me. I would like to thank you for encouraging my research and for allowing me to grow as a researcher. I would also like to thank my committee members, Professors Ismail Biskri, William Puech, Caroline Fontaine, Gouenou Coatrieux and Antoine Beugnard for serving as my committee members even at hardship. I also want to thank you for letting my defense be an enjoyable moment, and for your brilliant comments and suggestions, thanks to you. I would especially like to thank all of my friends and colleagues at UBO for their supporting and helping during my PhD trip.

A special thanks to my family. Words cannot express how grateful I am to my father, my brothers and my sisters for all of the sacrifices that you have made on my behalf. Your prayer for me was what sustained me thus far. At the end I would like to express appreciation to my beloved wife ESRAA who spent sleepless nights with me and was always my support in the moments when there was no one to answer my queries. Table 5. 5.14: Similarity metrics between w and w a in the case of image "hand" .................................. Table 5.15: Similarity metrics between w and w a in the case of image "brain 1" .............................. Table 5.16: Similarity metrics between w and w a in the case of image "brain 2" .............................. Table 5.17: Similarity metrics between w and w a in the case of image "leg" .................................... Table 5. 7.2: Similarity measures between w and w a based on PSNR, NCC and SSIM measures ......... Table 7.3: Comparison of the robustness of our method with some other related works [Guo 15] and [ Zheng 13

Table Of Contents

List Of Figures

List Of Tables

General introduction

With the huge developments and rapid growth in the technology field, Internet becomes the main communication media to transmit, share and exchange data between users. Internet provides fast, easy and low cost sharing way. But, it still produces a gap and a lack in the security and privacy issues such as integrity and authenticity. Moreover, the use of Internet as a central communication media of data opens new challenges and opportunities for duplicating, creating and manipulating the visual content of the digital material. Also, it opened new challenges in the field of illegal distribution and copyright issues which must be controlled. The ownership and the authorization to use the digital material also have to be proved.

On the other hand, one of the main concerns in the world is to develop the healthcare quality. The human healthcare is considered as the most important point throughout the world. The information technology contributes to the medical service improvement that is provided to people. Telemedicine represents the use of information and communications techniques to offer the health care where the patients and the physicians are disjointed by physical distance. The modern health care system like Hospital Information System (HIS) and Picture Archiving and Communication System (PACS) provide the health sector with the digital medical information like medical image in an easy and fast ways. The medical image is considered as a main core in telemedicine field. It is used for diagnosis in hospitals. So, any modification, even slight modification, will affect the physician's diagnosis.

Medical images request strong security to guarantee only the events of authentic modifications.

Interchange of medical images between clinics situated in different geographic places is a very commonly used way these days. But unluckily, this interchange happens through insecure and open networks, which create a threat of unfavorable acts and finally corrupted or lost data in the results. For these reasons and these threats, telemedicine has to provide security conditions of interchanges in order to guarantee the integrity and authenticity of the medical images during the transmission.

A huge amount of the medical images is captured in hospitals for diagnosis and research goals and are stored in databases. These databases must be protected against intentional and unintentional attacks and modifications. Such databases make possible to detect the disease and early treatments.

Meanwhile, the physician has to be sure that the image is free of manipulations before making the decision. For this goal, the watermarking is proposed as one of solutions to ensure about the medical image authenticity and integrity.

Using the authentication method provided by the watermarking, the physician will be able to detect some intentional alteration of the medical image and will not use such image to build the diagnosis.

Nevertheless, if the physician can be able to extract the embedded watermark perfectly, which usually takes a few seconds, he can continue safely with the diagnosis and treatments based on this image.

The watermark is not only authenticating the host image, but may also be useful in embedding extra information related to the host image. For example, information correlated to the patient as physician name, hospital and so on, are very useful in the telemedicine scenario.

The protection of digital medical image comprises at least two main aspects: security and authentication. In order to ensure the security, the information has to be protected from the unauthorized users while the authentication confirms that the received data is not affected or modified and is sent by the intended sender (watermarking). The cryptography technique proves the security issues by assuming the intended sender and intended receiver have some security aspects called keys.

So, after encryption of the digital material from the sender side, the person who has the key (receiver) can decrypt and access the content of the digital material.

Three main characteristics have to be ensured after the transmission of the medical image: confidentiality, authenticity and reliability. Confidentiality means that an authorized user can access and modify the medical image while an unauthorized user cannot access or take any information about the medical image. The user, at the destination side, who has the key, can decrypt the encrypted medical image and access to the patient information. Cryptography plays an important role to ensure this aspect. Authenticity is a characteristic that requires the fact that the received medical image at the destination is the same as sending from the source and belongs to the certain patient. Watermarking approach can achieve this aspect by a perfect extraction of the embedded watermark from the watermarked image. The third aspect is the reliability. It comprises the integrity and availability.

Integrity means that the received medical image must be intact from any modification. This aspect can also be achieved by extracting the exactly embedded watermark from the received image. The availability means that the medical image is available upon the request of the physicians or any medical party.

The cryptography approaches protect the data during the transition. The person who has the secret key and the algorithm can decrypt the data in a useful format. But after the decryption the data are no longer protected. Therefore, it is very hard to verify its integrity and its origin. This kind of protection is called priori protection methods. The watermarking approaches came as complimentary protection techniques to prove the data integrity, authenticity and its originality. After the data decryption, we still have the possibility to identify if the data is tampered or is in original form. This kind of protection is called posteriori protection methods [Bouslimi 12].

One of the goals of our research is to ensure and to prove the security of the medical image. This includes the authenticity of medical image and the proof of its integrity and its originality (owner).

Finally, this research focuses on supporting the health care system in order to implement a secure, robust and privacy system for the intact sharing and usage of the medical image.

In this thesis, we investigated the watermarking, cryptography and combined watermarking and cryptography approaches and apply them to telemedicine.

Thesis Organization

The thesis is divided in two parts. The first part includes the main principles and some of the previous studies in the watermarking, cryptography and combined watermarking and cryptography with a focus on the medical image field. This first part comprises four chapters (chapters 1 to 4).

In chapter one, we present the literature review of the digital image watermarking. We are focusing in this review on the robustness, imperceptibility and complexity properties in the existing approaches.

In chapter two, the cryptography approaches are investigated. Our goal is to focus on the complexity and security issues in the existing cryptography approaches.

Chapter three carried the hybrid watermarking and cryptographic existing approaches. Chapter four presents the telemedicine principle and medical image characteristics. Our aim is to show the importance of the medical image security properties and the gap in the existing approaches.

The second part presents our contribution based on robust watermarking in the spatial and frequency domain, informed and symmetric cryptography approach and joined (hybrid) watermarking and cryptography approach. This second part comprises 3 chapters (chapters 5 to 7)

Chapter five comprises five sections. The first one is the introduction. In the second section, we investigate a novel and robust watermarking approach in the spatial domain. Our approach is innovative and based on using Formal Concept Analysis. It proposes the generation of the optimal position for embedding. The watermark is built from some header information of the medical image.

It is embedded into the region of non-interest (NROI) of the medical image. Our goal is to provide watermarking solution with low computational complexity, high robustness, high imperceptibility and low degradation. In the third section, another robust watermarking approach is presented in the spatial domain. In this approach, we addressed the problem of generating watermarks as small as possible (small payload) based on ZBDD to adapt the hidden data to the real time applications by maintaining high robustness, high imperceptibility and low complexity within the medical image. The aim is to provide new adaptive watermarking method offering low complexity, high robustness and imperceptible watermarks. In the fourth section, we present a novel semi-blind watermarking technique in the spatial domain. The proposed algorithms covered two security issues: the tamper detection and the watermarking robustness. The approach is based on the Weber differential excitation descriptor. In the fifth section, we propose a new watermarking approach to ensure the CT scan medical image authentication and robustness, which is based on the wavelet transform in the frequency domain. The chapter ends with the conclusion.

In chapter six, we present our new informed symmetric cryptography approach. This approach exploits the characteristics of the image to generate the keys for encryption / decryption. It is based on N-gram technique. The main goal is to provide a solution for symmetric cryptography with more secure keys while maintaining low computation complexity.

Chapter seven deals with an innovative hybrid encryption and watermarking approach to improve the security and ensure the integrity of medical image content. It is based on one time pad (OTP) technique and a new formula of the chaotic map which provides a key matrix whose sizes is equal to the image size, where for each image pixel there is a mismatch-specific key value. The generated key stream used for the OTP cryptosystem is based on a new way of applying the chaotic map approach.

Here, the initial value of the key stream in the chaotic map is the same as the key used for watermarking. The properties of our chaotic map and OTP approach provided us with a reversible and predictable watermarking system.

FIRST PART

Digital Image Watermarking Chapter 1 1.1 Introduction

Digital Watermarking is the art of hiding secret information in the original data. The original data is readable and visual for all, while the hidden data is readable and changeable by the authorized user. It may be used to verify the authenticity and the integrity of the host signal or to show the identity of its owners. There is another field developed before watermarking for security issues: the steganography.

Watermarking is similar to the steganography. Both steganography and watermarking employ stenographic techniques to embed data covertly in noisy signals [Cox 07].

Steganography name is derived from the Greek where the prefix "stegano" means covered and the prefix "graphos" means write. The differences between steganography and watermarking are [Shih 07]: in steganography, the hidden information and cover information are unrelated each other, while in watermarking the cover and embedded data are related to each other. Also, in steganography, the message should be invisible, while in watermarking, it can be visible or invisible. Moreover, in steganography the main aim is to hide the data in a way the intruder cannot detect it, but in watermarking the main aim is to hide data such that the data cannot be removed or replaced by an intruder. So, the watermarking is more appropriate than steganography for preserving the security of digital images, due to its flexibility (choice between visible and invisible watermark, possibility to have a link between the hidden data and the host image) and because it makes it difficult to remove the hidden data. The data can be encrypted before embedding the watermark, as a second layer of protection [ Subramanyam 12]. As we illustrate in figure 1.1, the existing data security system is divided into information hiding and cryptography. Information hiding is also divided into watermarking and steganography. Watermarking techniques can be classified based on the human perception (visible or non-visible), based on reversibility (reversible or non-reversible), and based on the domain (frequency or spatial) [ Memon 10]. We will discuss the characteristics and classification of the watermarking system in the depth later on. In this chapter, in the first section, we discuss the definition of the digital image watermarking, the second section includes the characteristics of the watermarking techniques, the third section talks about the goal and the watermarking application, the fourth section discusses the classification of the watermarking embedding and extraction methods, the fifth section speaks about the visibility watermarking approaches, while the attacks and robustness will be discussed in the sixth section.

Finally, the quality image assessments will be discussed in the seventh section.

Properties of digital image watermarking

The digital watermarking system has important properties which must be achieved in the technique of watermarking. In this section, we discuss in details these properties:

Robustness

The robustness of the watermark is the ability to stand against different kinds of attacks. The common attacks are the image processing operations, like noise and cropping and geometric transformations like rotation and scaling. The attacks can be intentional attacks which try to remove and destroy the watermark in the watermarked image, or unintentional attacks, which are happening to the watermarked image during the transmission without aim to removing or impair the watermarked image. To measure the robustness, the following steps must be performed: apply different attacks to the watermarked image, then extract the watermark image from the watermarked image, and compare the original watermark with the extracted one.

In any attack cases, the robust watermarking approach has to resist and preserve the watermark image quality. These cases are:

1-Removal attacks like compression, which aim to remove the watermark, 2-Geometric transformation attacks like rotation, which aim to destroy the watermark, 3-Cryptographic attacks which aim to destroy the security key of the watermarking, 4-Property attacks which aim to add new watermark to the watermarked image.

The robustness as property is suitable to improve the copyright, the ownership issues and the medical application [ Malshe 12].

Imperceptibility

The imperceptibility [Shih 07] refers to the quality degradation between the original image and the watermarked image. Normally, the watermarked image should be perceptually similar to the original image. This property is called the imperceptibility or the transparency of the watermarking approach.

If in the watermarking process it happens that the original image after the embedding is affected, the whole technique is useless. In some applications which want the watermark to be perceptible for human eyes such as a logo for channels, a name of a person on some material and the other applications that want to show the owner of the materials, the imperceptibility can be low.

To evaluate the imperceptibility aspects in the watermarking system, we measure the fidelity between the watermarked image and the original image. The measurement tools show the degradation that happened to the watermarked image after the embedding. The common algorithms to measure the imperceptibility are Peak Signal-to-Noise Ratio (PSNR), Mean Square Error (MSE), Structure Similarity (SSIM) and Bit Error Rate (BER) [ Malshe 12]. We will discuss these tools in detail later on. Figure 1.3 shows an example of a watermarking approach with high and low imperceptibility.

Original Image Watermark Image

Watermarked Image (High Imperceptibility)

Watermarked Image (Low Imperceptibility)

Capacity and payload

The capacity refers to the available space of embedding in the original image, while the payload refers to the watermark size that will be embedded in the original image without noticeable to the reduction of the image quality and fidelity. The simpler capacity of a watermarking system is obtained with one bit for the watermark (Zero watermarks) [ Li 12]. Some of the applications require high capacity and low payload which means the watermark size is low (one bit) but will be embedded many times through the original image [Yaghmaee 15]. There is a trade-off between the capacity, robustness and imperceptibility. For instance, if the capacity is increasing, the robustness will decrease, while the imperceptibility will increase. Figure 1.4 illustrates the trade -off between the three properties. This aspect is very important for medical application, secure media, and other applications that want less capacity properties.

Security

A watermarking is secure if it is capable to fight intentional tampering attacks. It would include outstanding security even when the attacker knows the process for embedding and extracting the watermark. The power of the security of the watermark based on the key is selected. Let us consider the following scenario: the hacker attacks the watermark by removing it from the watermarked image and try to embed faked watermark. If the key used is secure, the system is considered as a secure system and it will deny the hacker. The security aspect is different from the robustness aspect. The robustness is surviving the common signal processing attacks. But the security is surviving the malicious modification. Some applications want to be secure while the others do not require it [Mousavi 14]. This property is desirable in multimedia security applications, ownership identification, fingerprint, telemedicine or medical image sharing.

Watermarking Requirements

Robustness Imperceptibility Capacity

Computational complexity

The watermarking system computational complexity is a very important and critical issue. In a watermarking system the size of the original image as well as the size of the watermark image determines the capacity. The capacity has an indirect influence of the computational complexity.

However, the time is the second important parameter of the complexity. The time complexity can be defined in terms of algorithm speed. To have a low complexity in time, the embedding and extraction processes time must be low. Moreover, the memory size of the equipment is important for the complexity. The watermarking algorithm complexity can be obtained by measuring the execution time of the embedding and the extraction processes [Cox 07]. This property is important and has to give a high consideration to the real time applications such as telemedicine, telediagnosis applications and online security application.

Blindness

The blind aspect is considered for the watermarking technique on the extraction side. The blind approach needs just the key. The non-blind system is more robust because the original image is available at the extraction process. But the blind system is the common way in watermarking. A blind system needs less memory space than a non-blind system.

Application of digital image watermarking

The watermarking is applied in many and different fields to achieve and/or to improve the security.

The watermarking approach can reach many security goals (copyright protection, transaction and finger print …). Each goal requires the appropriate properties among those mentioned in the previous section [Jabade 11] [Mousavi 14]. We can classify the most important applications as follows:

Copyright protection

One of the watermarking goals is to provide copyright for media material. It is about embedding the copyright information into the host image. The watermarked image has to resist against different kinds of attacks (removing, modifying, or adding new watermark). The technique proves the copyright owner into the material to avoid non-owners from claiming to be the legal owners of the data. The owner of the material can extract his/her watermark from the watermarked image to prove the right on the watermarked material. The watermarking approach in this application should be robust and invisible. Moreover, this application will not prevent the user from the copy of the digital image [ Kutter 99] [Wang 04 (a)].

Transaction tracking or fingerprinting

Fingerprinting requires the embedding of a different watermark for each customer. The watermark is usually related to the customer information like the customer identity. It makes it possible to track the images and to find where illegal copies are happening. Moreover, it makes it possible to detect the customer who breaks the rules and conditions of the agreements. This kind of application needs robust and invisible watermarking technique [Pankanti 99] [ Gunsel 02].

Authentication

The watermark is applied to the host image in order to verify its authenticity. In the extraction phase, the extractor can extract the watermark, then compare the extracted watermark with the original watermark to determine if the received data is authentic or not. These kind of applications deals with fragile and semi-fragile watermarking systems. Moreover, the original watermark it is required during the extraction phase [ Kundur 99] [Lu 01].

Integrity

The integrity aspects refer to the image safety. The watermark is embedded into the original host.

During the transmission process the watermarked image could be attacked (intentional or unintentional). The extractor will extract the embedded watermark and compare with the original watermark to verify its integrity. Any modification or small change in the watermarked image should be noticeable at the receiver side. This application requires fragile watermarking approach [Coatrieux 13] [Wong 98].

Tamper detection

Tamper detection is very critical in some fields as telemedicine in order to fight against counterfeiting of images. The hacker tries to tamper the watermarked image in unnoticeable way, where the normal user thinks it is un-tampered. The embedded watermark should be extracted by the authorized user.

The user has to know if the image is attacked or tampered and where the tampering happened. It is desirable of the approach to be a reverse approach, which means the technique can recover the original content after the watermark extraction. The watermarking system should be fragile [ Tan 11] [Fridrich 98] [ Lin 05].

Domains of image watermarking

Watermarking based on spread spectrum

The spread spectrum is a technique that is used in radio telecommunications in particular the military to disperse a signal over a wide band frequency so as to make it discreet and resistant to interference

[Wong 09].
It is clear that this model is immediately applicable to multimedia watermark.

We describe the approach proposed by [Bender 96] which is based on a pseudo pre-formatting the data to be embedded by dividing it at the image size. It then generates a random key of the size of the pre-formatted data and then applies a simplistic term binary operator "XOR" of this key and the spread data. It add the result to the host image for a sharp image. This is particularly interesting because it allows to expose several fundamental concepts of image watermarking algorithms namely the spread spectrum, the fact of using a secret key, amplitude modulation, etc ...

The watermarking system embeds the watermark information into the host image. There are many ways and techniques to embed the watermark or to extract it. Based on the algorithm and the way used to embed the watermark in the host image and to extract the embedded watermark from the watermarked image, we can classify the watermarking techniques into two main categories: spatial domain and transform domain with some of existing techniques as we illustrate in figure 1.5 [Mousavi 14]. In the next section, we will discuss the techniques in each domain. The weakness of the spatial domain in geometric attacks, especially in the noisy and compression attacks, is that the watermark can be easily changed by a third party [ Su 13]. There are many watermarking approaches applied in the spatial domain. We will review some of the common techniques in the following section.

Least significant bit (LSB)

Least Significant Bit (LSB) is known in the signal sample. It is exchanged in the input signal by embedding data bit in the least significant bit for the pixels. LSB is unnoticeable by the human eye.

The basic idea for LSB, is to present the pixel value into binary representation in 8 bits, then the LSB value is replaced with the watermark value: 0 becomes 1 and 1 becomes 0. Then the modified binary Let us assign the bit position from 1 to N, where N is the number of bits used to represent the data.

LSB will be the bit number In [Jain 14], the authors presented an invisible watermarking technique based on the LSB. The approach steps are calculating the height and width of the original image and the watermark image, and then scaling the original with scaling factor. After that, they generate a watermark object. Then embedding the watermark LSB set into the original LSB set.

Local binary pattern (LBP)

This approach is used for texture analysis and classification [ Ojala 02]. In LBP watermarking, the image is separated into non-overlapping square blocks, then the local pixel difference is obtained by calculating the spatial relative between the significant pixel and its adjacent pixel in each block. The local pixel difference is used for embedding and extraction of watermark and it is considered as the threshold. The advantages for LBP over LSB are the robustness against luminance modification, difference alteration and other attacks, and the weakness to other attacks such as filtering and blurring.

LBP can be used in semi-fragile watermarking techniques [Sachnev 09]. In [ Wenyin 11], a framework based on the Local Binary Pattern (LBP) in order to embed multi-level watermarking is proposed. The approach divided the image into non-overlapping 3 by 3 regions. Each local region is divided into three items: a vector containing the central pixel values, a vector containing the magnitude obtained from the differences between the central pixel and its neighbors and a vector of the sign value of the differences. The obtained vector's values are based on the Local Binary Pattern (LBP). The watermark is embedded by changing of the sign vector value in a local region. The approach was robust against some kinds of attacks like noise, contrast adjustment, luminance modification. Detector with Simulated Attacks (AHDSA) method. They applied simulated attacks to the original image to obtain the attack simulated image. Then, they determined the response threshold value in order to extract others features. The threshold was 20. AHDSA also provided them with the information about the location where the watermark should be embedded. This information is used as a key during the extraction process to determine the watermarking location. The extracted features and the watermark image have been embedded and extracted using a histogram based algorithm. The approach survived to geometric attacks like rotation, scaling, compression with low percent, cropping with percent up to 36%. The approach provided them with a capacity up to 128 bits. The image quality was decreased with the increasing of the capacity.

The histogram modification

Frequency domain

The frequency watermarking techniques are considered more robust than spatial watermarking techniques. Frequency domain or transform domain is more complex in computational complexity than spatial domain. The embedding and extraction process of all watermarking approaches in the frequency domain can be described as follows:

-The embedding process includes the image decomposition, watermark embedding and reversible image decomposing.

-The extraction process includes the image decomposition, watermark extraction and reversible image decomposition.

Among the frequency domain watermarking techniques, we can mention Discrete Wavelet Transform (DWT), Discrete Cosine Transform (DCT), and Discrete Fourier Transform (DFT) as the most known methods in the frequency domain. In the following section, they will be discussed in details.

Discrete wavelet transform (DWT)

Wavelets are mathematical functions. Discrete wavelet transform is a mathematical implementation for a hierarchical decomposition of an image. The transform is based on the waves called wavelets.

The wavelet provides the frequency and the spatial explanation of the image. DWT does a multiresolution decomposition description of the image. The decomposition procedure splits the image into low and high frequencies. The low frequencies contain the most important part of image information, while the high frequencies comprise the other information details. The watermark can be embedded in low or high frequency. Low frequency provides a good robustness, but with a degradation of the host image after embedding. Moreover, it is desirable to embed in the high frequency because it will not be noticeable by the human eye, but the robustness is low. Meanwhile, the wavelet transform deals with the compression, it provides a good robustness against JPEG attacks and filtering because the watermark is distributed through the image and is not located in specific pixels.

For one level DWT, the image is decomposed into four sub-bands: Low-Low (LL), Low-High (LH), High-Low (HL) and High -High (HH). In the case of two levels DWT decomposition, it produces another four sub-sub-band from the sub-band. We can reverse the approach by applying the inverse wavelet decomposition (IDWT). The general algorithm used for embedding the watermark in the original image is represented by the following formula:

(1.1)
where n is the watermark strength factor, s is the watermark embedding position, is the watermarked image, is the original image and is the watermark image.

The DWT schemes advantages comparing with the other techniques in the frequency domain are: good space frequency localization, multi-resolution properties, multi-scale analysis, flexible and simply adaptability to image, low complexity and a fast computation.

In [Ahmad 14 about the image while the high frequency contains the image details. If the watermark is inserted in the low frequency, the watermark will be robust but visible. Meanwhile, if it is inserted in the high frequency, the watermark will be invisible but less robust. So, the appropriate band is to embed the watermark in the middle frequency to avoid the image degradation and swap between the imperceptibility and robustness [Laouamer 15].

The DCT coefficient transformation of the signal is represented in the equation 1.5, while the inverse discrete cosine transform is represented in the equation 1.6 [ Laouamer 12] (1.5)

(1.6)
Where c(u), c(v) = (2) -1 / 2 for u, v = 0. And c(u), c(v) = 1 for u, v = 1,2,…,n-1. p(x, y) is the pixel value at position (x, y).

Figure 1.9 illustrates the general idea of the obtained image matrix after applying the DCT transform. The DWT transform is more suitable to human visual system than DCT transform. Also, DWT provides a multi-resolution decomposition, which can be shown at different levels of resolution and sequential procedures from low to high resolution. The DCT is based on a block which is not the case for DWT. Whereas, a higher compression ratio will affect in the blocks, and the visual artifacts are less evident in DWT than DCT. Meanwhile, DCT is a fully transforms frame which means any modification will be noticeable through the whole image while in DWT it is noticeable only locally [ Potdar 05].

The work in [Li 12] proposed a blind zero watermarking approach on the medical image features based on DCT. In the process the original image is transformed to DCT coefficients, then the 9 lowest frequencies are chosen: F(1,1),….,F [START_REF] Laouamer | Informed symmetric encryption algorithm for DICOM medical image based on N-grams[END_REF][START_REF] Alshaikh | Formal Concept Analysis to Improve Robustness on Medical Image Watermarking Schemes in the Spatial Domain[END_REF]. The value of low frequency coefficient is changed after attacks, but the vector of the signs of the coefficients remained unchanged even with strong geometric attacks. The feature vector is then generated. After that, watermarking and feature vector are used to generate the key sequence. The binary key sequence is computed by a HASH function. The key should be stored for using in the extraction process. One is used to represent positive or zero coefficient value while zero is used to represent a negative value for coefficients. In the extraction phase, the feature vector is generated. It consists of the signs sequence of the DCT coefficients. Then, the watermark is extracted by using the embedding key is extracted.

Low Frequency Middle Frequency High Frequency

The experimental results prove that the algorithm was robust and could detect the watermark without attacks, and with some common attacks (non-geometric attacks). But in the case of noise attacks, the image quality is not acceptable where the PSNR is around 10. In case of the filter attacks, the PSNR is around 20. Also, for JPEG attacks the PSNR is around 20. In geometric attacks, such as rotation and translation attacks PSNR are respectively around 12 and 13 dB. Moreover, the method provides a satisfying capacity; the computational complexity and the memory use are low.

The authors in [Lin 09] proposed a novel blind watermarking technique based on the DC components in the spatial domain. They merged the frequency and spatial domains in order to get better robustness and security for color host image. The proposed algorithm keeps the distribution features of the frequency coefficients and it has avoided the error resulting from the frequency transformation. The embedding steps were converting the image from RGB color into YCrCb color. Then, after obtaining the luminance Y of the YCrCb, dividing it into overlapped 8 × 8 pixel blocks. The method computes the DC coefficient C i.j (0,0) of each block. Based on the watermark information it decides the modifying magnitudes T1, T2. The possibility quantization can be computed by modifying magnitude T1, T2 and calculating the value for watermark embedding in DC coefficients for each block. Finally, the watermarked image is converted from YCbCr color into RGB color. In the extraction phase, the watermarked image is converted into YCrCb. Then, the luminance Y is obtained, and divided into 8 × 8 blocks. Next, the DC coefficient is obtained and the watermark value is computed. Finally, the inverse Arnold transform is applied to obtain the extracted watermark image. SSIM is used to measure the imperceptibility between the host image and the watermarked image (HVS). The proposed algorithm had high watermark invisibility and robustness against non-geometric attacks like JPEG compression and filter and geometric attacks like cropping, scaling, and rotation.

Singular value decomposition (SVD)

Singular Value Decomposition SVD is another frequency transformation method. It is a linear arithmetical implementation to decompose a matrix into its eigenvectors and eigenvalues. It has been widely used in the compression field cause its capability to provide the low rank calculation by alteration of an image into a new representation [Ranade 07]. The SVD can decompose a set of connected variables into unconnected variables. Moreover, singular values of an image are satisfying constancy, that is, when a small degradation is added to an image, it SV's do not modify significantly; and SV's represent mainly algebraic image features [ Liu 02].

Let us denote the image as I. I is a square image, N and M are the image dimensions. The SVD of I is defined as:

(1.7)
Where U and V are orthogonal matrices and S is a diagonal matrix.

The matrix U contains the left eigenvalues (left SVs) and the matrix V contains the right eigenvalues (right SV's), while the S matrix contains the eigenvalues (SVs). These singular values are arranged on the diagonal by a descending order where the highest value is the top left of the matrix while the lowest value is right down of the matrix. In watermarking schemes, after decomposition by SVD and embedding the watermark in a chosen matrix, the inverse SVD is applied to get a meaningful image.

In [Lei 14], the authors proposed a blind reversible watermarking scheme in order to ensure copyright protection of medical images. The approach uses the Recursive Dither Modulation (RDM) and the Differential Evolution (DE) optimization. They inserted double watermark into the original image.

Watermark embedding steps divide the original image into blocks. Then, scrambling algorithm is applied to both signature and logo data with an encryption algorithm to produce encrypted watermark text. Two levels wavelet transform were applied to each block and selected the low frequency coefficients. SVD was applied into low frequency wavelet coefficient for each block. The watermark was embedded by quantization using the RDM approach. After the embedding, inverse SVD and inverse DWT were applied to obtain the watermarked image. In the extraction phase, the watermarked image was divided into blocks. Then, two level DWT was applied. SVD algorithm was applied in the low frequency blocks to generate the singular values. Later, the singular values are normalized and the message shuffled, reshuffling the extract shuffled message. This last one was applied to obtain the watermark. The authors achieved a good balance between robustness, imperceptibility and capacity.

The algorithm has a high computational complexity.

Benhocine [Benhocine 13] proposed a new implementation of the SVD technique in the embedding and extraction process of an image watermarking approach. The authors purposed it to achieve a high robustness against geometric and non-geometric of attacks. They embedded the watermark in three cases of SVD. The first case was embedding the watermark in the three SVD matrices (U, S, V). The second case was embedding the watermark in U and V matrices. The third case was embedding the watermark in S matrix. The embedding is done using the linear interpolation 1.8 (1.8) where SVD represents the S, V and U matrices of the watermarked image, SVDw represents S, V and U matrices of the watermark image. SVDi represents S, V and U matrices of the original image.

. For the extraction process, it was done using the following linear interpolation (1.9) (1.9) where SVDwa represents the S, V and U matrices of the extracted watermark image. SVDwi represents S, V and U matrices of the original watermark image. SVDiwa represents S, V and U matrices of the watermarked image. The experimental results showed the robustness of the approach. Moreover, the watermark was imperceptible when t factor was close to one. The best quality to embed the watermark was in the S matrix. Some of the research works hybrid the techniques in the same domain or in different domains. For example, [Nema 14] and [ElGamal 13] hybrid DWT and DCT in the transform domain. The work of [Jose 12] combines DWT, DCT and SVD, while the works in [ Lenarczyk 13], [Oueslati 13] combined the spatial and frequency domain into image watermarking approaches.

Visible image watermarking 1.5.1 Visible image watermarking techniques

The watermarking techniques can be classified based on the human visual perception. The watermark can be embedded in a visible or in an invisible way. In some applications, two watermarks are embedded in the host image, one in a visible way and the other in an invisible way. This technique is called a dual watermark technique. One interest of this technique is that, if the visible watermark is attacked, the authorized user can retrieve the invisible watermark. Some applications require the watermark to be visible. This is for example the case of a logo of T.V. channel. The embedding visible watermark in the host signal will affect and degrade its quality. So the reverse watermarking technique is advisable with the visual watermarking in order to allow the authentic user to remove the embedded data and reestablish the original data. The main goal of the visual watermarking approach is to identify the ownership and the rights [Mousavi 14].

Visible image watermarking applications

In this section, we are reviewing some visible watermarking techniques. The visible watermark is desirable for fragile and semi fragile watermarking approaches. Moreover, it is used to improve the integrity, ownership, authenticity and tamper detection The authors in [Hsu 14] proposed a visible reversible watermarking technique. The watermark is a binary image while the original image is a grayscale image. They add to the original pixel values the watermark values directly. Then, the watermark information is hidden in the gray scale (watermarked) image in an invisible reversible steganography method. In extraction and reconstruction phase, the embedded watermark information is extracted and the watermarked image is reconstructed from the received image. After that, the watermark information is used to recover the original image. The authors provided double watermarking at the technique, the first one to watermark the original image in a visible way and the second one to hide the watermark information in an invisible way in order to recover the original image. In order to reduce the image size the authors compressed the first watermarked image before doing the invisible hiding steganography. The experimental results show a tradeoff between the watermark size and image distortion.

In [Weng 13], it is proposed visible reversible watermarking approach in order to protect the content integrity. The watermark is divided into many sub watermark images and the original host is a group of dynamic images. In steps are a capture of images, division and embedding of the watermark, generation of identification information and recovers and detects of the image. The generation of identification information can be used to produce the hash value avoiding tampered watermarks.

Moreover, the recovery and detection of image steps are used to ensure that the watermarked is recovered lossless and that the watermark is completely extracted. The proposed approach is a desirable solution for copyright protection and tamper detection. It can confirm the data integrity.

The work in [Tsai 10] presents a visible reverse watermarking approach in order to improve the original data authenticity and transparency. The approach comprises three stages: visible watermarking, protection and transparency compromise and reversible data embedding. In the visible watermarking, the watermark is embedded in the original image based on the pixel value mapping function. In protection and transparency compromise, the hash value of the original image is encrypted by the secret key. Then the generated sequence integer which is built from the zero mean and distinction variance is added to the visible watermark. The integer sequence avoids repairing an original image also it overrides the trade-off between transparency and robustness. In reversible data embedding, the authors embedded the recovered data and the authentication data based on the current reversible data embedding system. The authorized user can retrieve the original image while unauthorized user will retrieve the image with the added integer values noise.

Digital image watermarking attacks and robustness

The robustness is the strength of the watermarking approach against the general attacks. The robust watermarking preserves the watermark through the transmission process. If intentional or unintentional attacks are happening, the authorized user can retrieve the watermark with high quality.

This aspect is necessary in copyright application, the ownership issues and the medical application.

The common and image processing attacks will be discussed. Moreover, some of the watermarking approaches that focus on robustness will be presented.

Digital image watermarking attacks

The attack is this process aiming at destroying, manipulating and impairing the detection of the embedding watermark. Watermark attacks include unauthorized embedding, unauthorized detection, unauthorized removal and system attack. Known Original Attack (KOA) happens to watermarked and original content. Known Message Attack (KMA) happens to watermark contents and hidden messages. Watermark Only Attack (WOA) happens to watermarked contents [ Kavadi 12] [Voloshynovskiy 01], [ Malshe 12], [ Song 10] classified the watermark attacks into four categories explicitly Removal Attacks, Geometric attacks, Cryptographic attacks and Protocol attacks.

Removal attacks are those removing the watermark from the watermarked image, but they do break the security of the watermarking algorithm. Also, they preserve the content so the cover image is still available after the end of the attacks. After a removal attack are cannot rebuild the watermark image from the attacked watermarked image. Examples of these kinds of attacks are noisy (Gaussian, Salt and Pepper, uniform), compression (JPEG, JPEG 200), filtering (Mean, Median, Gaussian), histogram and sharpness attacks.

Geometric attacks are different from the removal attacks. Geometric attack aims to destroy the watermark image rather than to remove it from the watermarked image using the geometric distortion.

It is still possible to rebuild the watermark after the geometric distortion if the detail of the attack can be built. The method to correct this kind of attacks is called synchronization. Examples of these kind of attacks are cropping, rotation, translation, skewing.

Cryptographic attacks aim to destroy the security feature in the watermarking system, then to find how to remove the watermark embedded and try to embed a deceptive watermark. The example of this kind is the brute-force search method which tries to break the watermarking security by using a large amount of the possible meaningful security information. Another example is an Oracle attack which is trying to create a non-watermarked image at the decoder side if the decoder policies are accessible.

The protocol Attacks are aiming to add the attacker watermark in the watermarked image rather than to destroy or remove the watermark image and it will give the attacker the right in the ownership of the cover image. Moreover, it can estimate the watermark image from the watermarked image and copy it to another data called target attack.

Robust image watermarking approaches

In [ Subramanyam 12], Subramanyam et al. proposed a robust watermarking of compressed media for tamper detection, ownership declaration, or copyright management purposes. The proposed technique is dividing the input image into non-overlapping rectangular tiles. Then, it is applying the DWT technique. In result, multiple levels of DWT give a multi-resolution image, the lowest resolution contains the low-pass image, higher resolution contains the high pass, the resolution is divided into smaller blocks known as code-blocks, and each code encodes independently. The extraction of the watermark was done after decryption of the image. They analyzed payload capacity and quality of the image for different resolutions. The experimental results showed that the higher resolution carries a higher payload capacity without affecting too much the quality, and middle resolutions carry lesser capacity and leads to more degradation in the quality. This approach is weak against noise and filtering attacks.

In [Moghaddam 13], the authors applied new robust blind watermarking techniques based on an imperialist competitive algorithm (ICA) in the spatial domain. Firstly, the approach determines the location in the host image to be selected based on modified ICA. Secondly, 5 by 5 neighbors of the modified block are chosen and the least significant color in the neighborhood of each pixel is selected for embedding, then the best neighborhood which will increase the quality of the watermarked image is selected. The proposed approach is applied in the spatial domain in order to find the optimal position of embedding. It is robust against some kinds of attacks, but it is still weak against compression and sharpening attacks.

Wang et al. [Wang 14] improved the sample projection approach in order to achieve copyright protection. In this approach, they produced the enhancement of the code lines by inverting the sample projection approach. The improvements considered two aspects: lower distorted code lines and constructing long line segments. Lower distorted code line purpose is to reduce the distortion during the embedding process, while constructing the long line segments provides more robust and secure to prevent the unauthorized user from guessing the watermark. This approach was developed from a previous approach of sample projection. It is considered better in robustness against Gaussian, filter and compression, but weak against rotation salt and pepper noise, and AWGN noise.

The work in [ Gu 13] proposed new reversible and robust watermarking approach. They used the chaotic map scheme in order to find the optimal embedding position in the original image and also to find a threshold space of reversibility. These threshold works as adaptability between reversibility and robustness aspects. The approach crops the original image into a smaller image. The obtained image is divided into non-overlapping blocks with size 6 × 6. The chaotic map is iterated using equation 1.10 to avoid the damaging result algebra fraction operation (1.10) where is the parameter of n th iteration and is given.

The integer wavelet decomposition (IWT) one level is applied. The low level sub bands with size 3 × 3 for each block are chosen and the number of the optimal position in the LL is obtained using the equation 1.11:

(1.11)

where n starts with 5 which is considered the central pixel of the LL block. After finding the embedding position, the watermark is embedded. Then, inverse integer wavelet transform is done for each block with the new value of the LL sub band. The watermarked image is gotten. In the extraction phase, the initial values of the x 0 in the chaotic map and the chaotic map are assigned and they are the same value that is used in the embedding phase. Repeating the embedding steps including the cropping of the watermarked image, smaller image is obtained by applying IWT to get 3×3 low level blocks. The optimal numbers of n are found and the embedding position is gotten. Then, extract the watermark from the obtained position. The approach achieved a balance between the reversibility and the robustness. Moreover, the threshold values control the robustness and reversibility, but if the threshold is equal to 40 the approach is not reversible. The highest robustness is obtained when the threshold is equal to 12.

In [Thabit 14], the authors are presented a robust and lossless watermarking approach. The approach is based on the Slantlet Transform (SLT). After the modification of the sub band coefficient, the watermark will be embedded in the high frequency sub band. The approach is applied in the color medical image, general image and synthetic aperture radar image domain. The watermark can be embedded in three channels of image colors in order to achieve enough capacity. The embedding steps are the following: divide the original image into blocks. Then, apply the SLT decomposition for each block using the equation 1.12:

(1.12)

where s is the original image dimension, S is the SLT decomposition, SLT N is N × N SLT matrix.

After the SLT decomposition, the high frequency (low-high and high low) sub band is chosen. After, calculating the mean value for each sub band, they modified the difference between the mean values of the SLT coefficient in the high frequency band. The watermark was a bit and when the value of this bit is 1, the mean value of the high-low sub band SLT coefficient is more than the mean value of the low-high SLT coefficient. While the value of the watermark is 0, the mean value of the low-high SLT coefficient is more than the mean value of the high-low sub band SLT coefficient. Then, the inverse SLT is applied to get image block and pixel adjustment to obtain the watermarked image. In the extraction process, the watermarked image is divided and the SLT decomposition is applied. Calculate the mean value for each block of the coefficient in the high frequency. Then the watermark will be extracted based on the mean value of the SLT coefficients. If the mean value of the SLT coefficient of the high-low sub band is larger than the mean value of the SLT coefficient of the low-high, the watermark will be one. But if the mean value of the SLT coefficient of the low -high sub band is larger than the mean value of the SLT coefficient of the high-low, the watermark will be zero. The proposed approach provided high quality, capacity, imperceptibility and robustness against intentional and unintentional attacks.

watermark is embedded in the host matrix. In the extraction phase, the same embedding decomposition is applied to the watermarked image. Then, the watermark is extracted. The proposed approach is a suitable for the tamper detection and perfect authentication. It can find the tampered blocks and then location. The approach doesn't cite the geometric attacks.

Image quality measurement

The objective image quality metric shows a difference of roles in image processing uses. Firstly, it may be used to monitor and regulate image quality, such as to evaluate the transmitted image through the internet to control and allocate the resources. Secondly, it may be used to optimize the process and settings of image processing methods. For instance, the evaluation metric can support the optimal design of pre filtering and bit task algorithm at the encoder. Meanwhile, it supports the decoder in optimal reestablishment, error hiding and post filtering system. Finally, It may be used to benchmark the image quality processing approaches and algorithms [Wang 04].

The image quality can be measured for the watermark or the original image in order to assess the watermarking system. Image quality can be valuated using different methods. The optimal manner to make the visual experiment under controlled conditions is such that the human viewers can note the image quality degradation. Image quality assessment evaluates the original image by comparison with the watermarked image in order to see how the embedding effect on the image quality. Moreover, the assessments evaluate also the extracted watermark by comparing with the original watermark to measure the approach robustness [Dumic 14].

The objective quality assessments can be classified according to the reference image into three categories: full reference, non-reference and reduce reference. The full reference is the reference following which the evaluated image exists during the evaluation. If the evaluation is done without the original (reference) image, the evaluation is called non-reference or blind. In reduce reference, the original or reference image does not exist, but the extracted features information about the reference image is offered during the evaluation [Wang 04].

In the evaluation way, some of the existing techniques are based on pixel evaluation are: Mean Square Error (MSE) [Wang 09] [ Tan 13], Peak Signal to Noise Ratio (PSNR) [Tanchenko 14] [ Chauhan 13].

Some of them are based on the structural distortion like Structural Similarity (SSIM) [ Rehman 12] [Zengzhen 14] [ Tan 13]. In the following section, we are reviewing the most common algorithms in the watermarking image quality measurements.

Mean square error (MSE)

The mean square error is the average of the squared intensity differences between the original image and the watermarked image or between the extracted watermark and the original watermark. It is commonly used in the image quality measurements, because it provides a good approximation of the image quality degradation, it is fast in applying and easy in computing. To compute the MSE between two images, the following equation is used:

(

where I and are the original image and the watermarked one, respectively. m and n are the images size [Wang 09].

Peak signal to noise ratio (PSNR)

The PSNR is a distortion measure used in digital image, specifically in any image compression. It consists in quantifying the performance of the encoder by measuring the quality of reconstruction of the compressed image compared with the original image. PSNR is defined by:

(1.14

)
where P is the image depth. PSNR is depending on the MSE value of the reference image and the watermarked image. If the PSNR value is greater than 30 dB, the image quality is acceptable. A higher PSNR value means that the similarity and fidelity between the two images are better and the degradation and the distortion are lower [Tanchenko 14].

Structural similarity index measurement (SSIM)

PSNR and MSE quality measurement tools are based on the bit errors between the original and distorted images. There are full reference tools and statistical average in the evaluation, where the evaluation is obtained to be closer to the human visual system (HVS). SSIM is a quality measurement tool based on the structural similarity. The system of similarity measurement is comparing three components of each signal the luminance ( , contrast (c) and structural(s) [Wang 04].

The luminance is computed based on the following equation:

(1.15)
where m and n are two nonnegative images. is the mean intensity of the image z. and is small contrast and very close to zero.

To compute the second comparison of the structural similarity, the contrast of each image is calculated as the following equation:

(1.16)
where is the standard deviation of the image z, is small contrast and very close to zero.

The structural comparison is defined by the following equation

(1.17)
where is the covariance between image m and image n, is small contrast and very close to zero.

After calculating the three components, we combine them and the SSIM is defined as follows:

(1.18) where are the parameters to control the relation importance of the three components.

Bit error rate (BER)

Bit error rate also called bit error ratio is the number of receiving bits that have been altered, modified or even destroyed during the transmission process, divided by the total number of transmitting bits.

Normally, it is expressed as a percentage. The low percentage value refers to a high quality and low degradation of the received data [ Zhang 13].

BER is an efficient measurement tool in signal processing. It is widely used in the watermarking field.

BER measures the extracted watermark by correlating to the original watermark to prove the robustness of the watermarking method, or it measures the recovered image by correlating with the original image. The reliability of the watermark is correlated with the robustness and capacity aspects [Zhang 07].

In the watermarking approach, one measures the extracted watermark bits by correlating to the original watermark bits, in order to determine the degradation percentage in the received data using the following equation:

(1.19)
where erfc is the error function, is the original watermark and is the attacked watermark.

Conclusion

In this chapter, we have presented a state of the art of the techniques currently used in digital image watermarking. These techniques can be classified according to the method used for the embedding of the watermark or following the embedding area. Depending on the way of embedding, the techniques are considered as belonging either to the spatial domain or to the frequency domain. This state of the art has enabled us to identify the main lines leading to the design of a watermarking system and revealed the diversity of techniques used. However, the robustness of the watermarking is mainly checked visa-a-visa the existing standard attacks. Most efforts have been done towards an adequate management of compromise between robustness and visibility. Moreover, the notion of similarity has been introduced to measure the degree of resemblance between the original watermark and the one extracted after an attack and that allows determining the robustness of watermarking schemes. These measures are often metrics that quantify the proximity of spatial images in their characteristics.

The analysis of previous watermarking approaches has led us to the conclusion that the watermarking approaches in frequency domain still present some gaps against some scenarios of attacks, and also for the imperceptibility which remains a negotiate issue. However, the existing solutions based on spatial domain provide not enough robustness against attacks with high watermark payload.

Moreover, the computational complexity in watermark embedding/extraction has to be taken into account especially for a real time application.

Chapter 2 Digital Image Cryptography

Introduction

The protection of digital information comprises at least two featured problems: security problem and authentication. In the security problem the information has to be protected from the unauthorized users while the authentication confirms that the received data is not affected or modified and original as the intended sender. The cryptology technique proves the security issue by assuming the intended sender and intended receiver has some security aspects called keys. These keys can be the same with the sender and receiver sides (symmetric) or can be different which means the key used at the sender side is different from the key used on the receiver side (asymmetric). The algorithm used in the symmetric encryption is known as a cipher. Encryption algorithms are classified into block and stream cipher depending on the way the data are processed. Moreover, cryptography ensures the security issues such as confidentiality, authentication and reliability. Confidentiality aspect refers to the user who can access to the data, the authorized user who can read the data and the unauthorized user who does not have the permission and the access possibilities to the electronic data. The confidentiality is maintained under using the secret key, so the person who has that key will be able to read the data [Zhu 14] [ Eslami 13]. While, the authentication is the action of confirming that the received message is the unaffected and the original sending messages from the sender. The authentication of the digital message proves there is no modifying or altering through the transmission process and received without any tampering [ Gong 13] [ Rajput 12].

Furthermore, the reliability comprises the integrity and the availability. The integrity is the ability of the authorized user to modify, insert, delete and update the data and detecting the modification happened by the sender or the receiver. So, for each different message there is a different fingerprint encrypted by the secret key. The availability is the property that data can be available for the authorized user to be usable and accessible [Bouslimi 12] [Ran 14].

Cryptography: definition and principle

Cryptography is the art of encryption and decryption data in order to protect them during the transmission or the storage. The cryptanalysis is the art of studying and analyzing the cryptographic approach [Mel 01]. The cryptography and the cryptanalysis have a robust relative. In the next section, we will discuss the encryption and decryption phases in cryptography domain.

The main goal from the encryption is to insure the security of the sending message by reproducing the message in an unreadable way and sending it in the unsecure channel. The decryption phase consists in rebuilding the original message from the encrypted one. The general encryption and decryption scheme can be summarized in two phases as shown in figure 2.1: the encryption is denoted by E and the decryption D, where D is the reverse of E. The sender encrypts the original data P (the plain text), then transmits the encrypted data.

Cryptography classification

Cryptographic approaches can be classified into three main categories: symmetric, asymmetric and function encryption can be divided into: keyed hash function and un-keyed hash function. In the cryptography classification section, we will discuss the encryption algorithms categorization in detail.

We present, according to [Menezes 97], the three categories: symmetric, asymmetric and hashed key as shown in figure 2.2.

. The symmetric techniques can be divided into two categories: stream cipher and block cipher.

Stream cipher

In the stream cipher, the plain data will be a stream of data like bit or byte. It encrypts one character at the same time [ Kotulski 99]. Normally, the key is a pseudorandom number sequence applied to the plain text to generate the cipher text and that sequence will be applied to the cipher text to produce the plain text. This method is suitable for simple and fast application encryption because it uses small storage and buffer during the encryption and decryption process. Meanwhile, it takes long time for the huge data encryption application since it doesn't deal efficiently with the real time applications [Golić 97] [Gupta 14].

Block cipher

The block cipher is an encryption way applied to a block of text using a secret key. In general, it takes less time than stream cipher and more storage during the encryption and decryption process, but it is suitable for large data encryption application [ Kotulski 99].

Asymmetric cryptography

Asymmetric cryptography is also called public key or two key encryption methods. In 1976, Diffie and Hellman published the first paper about the public key encryption. In that research, the authors formulated and introduced a new contribution in the cryptography field [Diffie 76]. Normally, the first key is called public; it is used in the encryption phase, while the other key called private is used in the decryption phase or conversely, the private to encrypt and the public to decrypt [Bellare 95]. The sender encrypts the message (plain text) using the encryption algorithm and the public key to generate the cipher text. At the receiver side, it decrypts the cipher text using the decryption algorithm and the private key to get the original text as in figure 2.6. If the receiver can understand the decrypted message, the message is an authentic message and the receiver assumes the message encrypted using the public key of the sender. Else, the receiver drops the decrypted message and he will know that it is an inauthentic message.

Block Cipher key

A 1 A 2 . . A n B 1 B 2 . . B n

Figure 2.6: Encryption and decryption process based on asymmetric technique

The advantage of these techniques is that they do not require a security in transmission channel but they have major problems, particularly in term of calculation time. The general diagram of the encryption and decryption process of the asymmetric technique can be summarized in the following equations:

(2.3) (2.4)
where E is the encryption algorithm, P is the plain text, C is the cipher text, k1 is the public key, k2 is the private key and D is the decryption algorithm.

In the asymmetric technique, the sender and the receiver have to generate a key, one of them will be shared during the transition process while the other will be hidden and secure from the hacker and unauthorized user [Menezes 97]. The security of the asymmetric technique is based on the algorithm used and on the two keys especially the private key. The most known techniques based on the asymmetric technique are RSA [ Harn 13], DSA [ Kim 13], ELGAMAL [Khedr 14].

Hash function cryptography

Cryptographic techniques

In this section, we will present the most known techniques in the symmetric and asymmetric domains.

Symmetric encryption algorithms

One time pad encryption (OTP)

OTP is a stream cipher symmetric encryption technique. The general idea of OTP is to use a unique key for each letter or number. The key is used to encrypt letters or numbers in the plain text. The key didn't repeat again in the encryption keys at that time (one-time). The sender and the receiver must have a copy of the pad. In the encryption phase, the original message (plain text) is merged with the random strings using an XOR process, while the receiver decrypt the cipher text based on the same encryption key and reversing the encryption process. Theoretically, OTP is hard to break because for each string we use a unique and not repeated key. It is difficult to use since both the sender and the receiver must have the copy of the pad. Moreover, the key length has to be the same length as the plain text which is impractical and inefficient for large data encryption system [Dube 08]. The following equation explains the general idea of OTP encryption and decryption process: In the encryption phase, the plain text process through 16 circles and each circle has a sub key of size 48 bits. This sub key is generated from the secret key of the size 56 bits. The plain text is divided into two values with the same size (32 bit). In the decryption process, there is the same number of iterations, but with the reverse order of the key (from K n to K 1 ).

Rivest-Shamir-Adleman (RSA)

In 77, the new asymmetric algorithm is proposed based on a public and private keys cryptography algorithm, the Rivest-Shamir-Adleman (RSA) algorithm. RSA uses variable input message length and variable secret key length where the key is derived from the very large number, which is the product of two large primary numbers selected based on specific instructions [Rivest 78].

The encryption key is public and it is different from the decryption key (private). The public key is generated from the two primary numbers and it is shared while the private (primary numbers) is kept in hidden way. The user can use the public key for the encryption process, but the user who has the primary numbers can decode the cipher text. During the key generation, two keys are provided: one of them is public, it can be known by anyone and it is applied through the encryption process. The decryption process is done using the private key.

In encryption phase, the sender shares the public key with the receiver while the sender keeps the private key secret and performs the encryption process as shown in the following equation:

(2.7)
where c is the cipher message, m is the plain message, k 1 and k 2 are the public keys.

In the decryption phase, the private key has to be provided by the authentic user, and the module base is still the same encryption module base. The process is done as the following equation:

(2.8)
where k 3 is the private key. In digital signature approach, the public file contains the public key which is provided to any user. To sign the document, a user has to use the secret key. Any user can verify the authenticity using the public key, but the authentic user can forge the signature. The signature builds based on the following equation:

ElGammal encryption

(2.9)

where is the signature, m is the message to be signed, y is the public key, p is a large prime number, r and c is the pair (private and public) keys of m where .

In the verification phase, we verify the authenticity of the message signature by computing the both sides of the previous equation.

ElGammal has some specific properties. It is a randomization encryption operation. The cipher text for a certain message is not repeated, encrypting the same message twice provides us different cipher messages. The specific structure of the approach is that there is no clear relation between the approach functions [ElGamal 85].

Cryptanalysis

Cryptanalysis is both the art and science of the break of the cipher message without knowing the keys. It tests the algorithm robustness against attacks, or from unauthorized user to deciphering the secure message. The process depends on the nature of the technique and on knowing the properties of the original message and the cipher message. From the available information about the properties the user tries to achieve the key. MAC algorithm needs more cryptanalysis offers. In the hash function, the cryptanalysis center is on the inside structure of the compression technique [Chakraborty 14].

Differential cryptanalysis is a technique for breaking the cryptosystems. It was designed in 1990 by

Eli Biham and Adi Shamir [Biham 91]. Differential cryptanalysis is effective when the cryptanalyst can select plaintexts and obtain ciphertexts. The process searches for plaintext, ciphertext pairs whose difference is constant, and considers the differential performance of the cryptosystem. The difference of two elements P 1 and P 2 is defined as P 1 XOR P 2 for DES [ Biham 12]. The difference may be defined in a different way if the process is applied to some other cryptosystem.

Several attacks have been applied to cryptography algorithms. In the next section, we will discuss the most known of them.

Brute-force attack

Brute-Force attack is one of the attacks whose purpose is to break the cryptography algorithm by searching all the possibilities for the used keys till achieving the correct one. The resistance of any cryptography techniques against brute force attacks depends on the key length as more is the time to find the possible key from the existing information. It means the key size plays an important role and that the longer key size is more difficult to achieve. Any system that can discover the secret key faster than the brute force attack is measured an effective attack [ Kahate 13].

In the hash function cryptography technique, the robustness of the algorithm against the brute force attack is very weak, because the number of the inputs and the outputs of the hash function are infinite.

Moreover, the hash function requires to find two messages of changed lengths which hash to the similar hash value [Gupta 14 1]. [William 06] produced brute force attacks which applied to MD5 cryptographic algorithm. The author concluded for hash code of size 160 bits, that's the time to find the required collision is over four thousand years. The collision is to find two different length message with the same hash value [William 06]. However, the hash function is never allowed collision and the strength of the hash function depends on the length of the hash function technique. ]. We can say the algorithm is collision resistant if it is complex computationally to find two different inputs that have the similar and equals outputs. Birthday attacks in hash function cryptography require around 2 f/2 processes where f is the size of the hash value in bits. For SHA-1 of 160 bits, birthday attack needs 2 160/2 (2 80 ) hash processes.

Birthday attack

Meet in the middle attack

Meet in the middle attack is used to realize dual encrypted secret key of block cipher technique. The attacker is expected to access the plain message and the cipher message. He tries to encrypt the plain message by different keys. Meanwhile, it decrypts the cipher message in different keys in order to find the middle value of the encrypted plain message and the decrypted cipher message. Figure 2.9 illustrates the general diagram for meet in the middle attack.

Conclusion

In this chapter, we have presented the main concepts and principles of cryptography field.

Cryptography area comprises: symmetric (private), asymmetric (public) and hash function techniques.

Symmetric techniques are divided into stream cipher such as RC4 and block cipher such as DES. The symmetric approaches have a gap in the security issue of sharing the key while the asymmetric approaches take a long execution time. On the other hand, the symmetric techniques allow achieving less computational complexity compared to asymmetric techniques while the latter provides a more secure key.

A= K n E= K d E= K d B= K m

Alice

Eve Bob

Chapter 2: Digital Image Cryptography Hybrid Watermarking and Cryptography Techniques Chapter 3

Introduction

The cryptography approaches protect the data during the transition. The person who has the secret key and the algorithm can decrypt the data into a useful format. But after the decryption, the data are no longer protected and it is very hard to verify its integrity and its origin. This kind of protection is called priori protection methods. The watermarking approaches came as a complementary protection techniques to prove the data integrity, authenticity, its originality, availability, etc…. After the data decryption, we still have the possibility to identify if the data is tampered or if it is in original form. This kind of protection is called posteriori protection method [Bouslimi 12].

We discussed in the previous chapters the security issue for watermarking and cryptography separately. In this chapter, we will discuss the combination of watermarking and cryptography together. The encryption is a common way to secure and prove the data confidentiality. The second section presents the four known ways to combine the watermarking and encryption approach classifications.

Combined watermarking and encryption approaches classifications

The combinations of watermarking and encryption techniques are well-known. They can be classified according to the approach of combination as follows:

Watermarking followed by encryption (WFE)

In these kinds of approaches, the watermark is embedded in the host data, then the watermarked data are encrypted. On the receiver side, the watermarked encrypted data are decrypted, and after that the watermark data are extracted. here, i, w, s are the original data, the watermark data and the secret key in the embedding/extraction algorithm, respectively. i w is the watermarked data. k is the secret key in the encryption/decryption algorithm. Ei w is the encrypted watermarked data. Di w is the decrypted watermarked data.

In [Taneja 13], the authors proposed watermarking and encryption approach. The watermarking is done based on the Wavelet Packet Transform (WPT) and Singular Value Decomposition (SVD) methods, while the watermarked data is encrypted based on Set Partitioning in Hierarchical Trees (SPIHT) provided by developing the framework JSON Web Encryption (JWE), in order to ensure the data confidentiality and the content ownership.

In [Kannammal 14], the authors also proposed a dual watermarking and encryption approach in order to prove the authenticity and integrity of medical images. Two levels DWT transform is applied to the original data. The watermark is embedded in the low-high sub-band based on the Least Significant Bit (LSB) where low-high sub band is divided again into many blocks, then the medical information (as a second watermark) is embedded into these blocks also based on the LSB technique. The watermarked image is encrypted using the RSA, AES and RC4 algorithms. In [Saha 14], a hybrid encryption and watermarking image approach is proposed in which the encryption is done using One Time Pad (OTP) method while the watermarking is done based on discrete wavelet transforms. The key was built from each 8 by 8 block of the image. The watermark is encrypted using the XOR, then they embed the encrypted watermark in the original image in the middle frequency sub-band of the DWT coefficients. The weaknesses in this technique are the following: the key is extremely large to share, the way to produce the key is fragile, and the imperceptibility results are unacceptable. Moreover, the authors didn't measure the robustness of the their watermarking algorithm and also didn't test it against attacks.

In [ Pradhan 12], the authors proposed a watermarking scheme based on the Discrete Wavelet Transforms (DWT) applied to an image. The original image is decomposed using DWT and the medium frequency sub-bands are chosen for embedding. Then, Arnold transformation and Cross chaotic sequence are used to encrypt the watermark. The DWT transformation is applied to the encrypted watermark image and the medium frequency coefficients of the encrypted watermark image are embedded in the medium coefficients of the original image. The complexity of the proposed approach was very high due to the dual encryption on the watermark image. Also, there is a remarkable degradation of the retrieved original image after applying attacks.

The work in [ Zhang 11], the authors provided a novel and reversible watermarking approach for the encrypted image. After encrypting the whole data of an image based on a stream cipher way, the watermark information is inserted into the image by adapting a slight quantity of encrypted image. At the decryption side, the encrypted watermarked image is decrypted by using the encryption key.

While the watermark key is obtained by, support of spatial relationship in natural image, the embedded data can be successfully extracted and the original image can be perfectly recovered.

The authors in [Wu 14] proposed reversibile data hiding in the encrypted domain approach. The authors is used two reversible data hiding techniques in encrypted images, called a joint approach and a separable approach. The approaches have been introduced by assuming prediction error. In the joint approaches, the extraction and image rebuilding are made at the same time. The reversibility provided by the number of incorrect extracted bits while the approach achieved good visual quality of recovered data, particularly when embedding amount is high. In the separable approach, the extraction and the recovery of the image are disjointed. The separable approach provided enhanced reversibility and good visual quality of recovered image for high payload embedding.

Joint watermarking / decryption (JWD)

The method is considered as a secure embedding, where the watermarking technique is applied to the decrypted data on the receiver side. The sender encrypts the data and transmit them through the internet, the receiver receives the encrypted data and the unique specific information about the decrypted key (Client Specific Decryption Key (CPDK)). The decryption process and the watermarking process are convoluted and done at the receiver side, which means the decrypted result with the specific CPDK of the receiver produces content copy personalized of the receiver. JWD limits the bandwidth usage, reduces the server (sender) complexity. Moreover, it is useful in forensic tracking, fingerprinting and ownership identity applications [Celik 07].

The JWD general diagram is illustrated in the figure 3.5 In JWD approach, the sender generates different and unique key for each receiver that is used to decrypt and to embed the watermark. After the decryption, the watermark is embedded into the decrypted data (plain data) to obtain the watermarked data.

In [Kundur 04], the authors proposed video fingerprinting and encryption approach for digital rights controlling. They encrypted the sign of all the significant Discrete Coefficient Transform (the middle frequencies) for each frame, while they provided each user with a private decryption key to decrypt just the subset of these coefficients. The remaining coefficients knotted the form of the fingerprint.

The approach was perfect in its encryption phase, but the lack of effective discovery tools and security procedures limit its prospective using.

Bouslimi et al in their work [Bouslimi 14], presented a novel cryptography and a watermarking approach for medical image securing. They proposed a pair of existing watermarking technique based on Quantization Index Modulation and JWD approach. They insert dual watermark, one of them before the encryption includes the reliability evidence, and the other during the decryption process (JWD) includes traceability evidence. The authors' goals are to guarantee the confidentiality, the reliability and the traceability to identify the origin of the unlawful distribution of the medical images.

Joint watermarking / encryption (JWE)

In this way, the watermark is embedded through the encryption process which means merging the watermarking and encryption together at the sender side. In JWE, the watermark can be extracted in the spatial domain after the decryption, or in the encrypted domain from the encrypted image, or both of them [Bouslimi 12]. The general diagram of JWE is illustrated in the following figure. The experimental results showed a low image distortion and sufficient capacity to embed a reliability evidence. Its approach is slower than image encryption algorithms, but the execution time for the decryption process is not impacted. Another watermarking and encryption approach was proposed also by Bouslimi et al in [Bouslimi 12 (c)]. The watermarking algorithm comprises two watermarking approaches: least significant bit and quantization index modulation, while the encryption algorithm is based on stream cipher RC4.

Conclusion

In this chapter, we presented the combined watermarking and cryptography approaches. The joined watermarking and cryptography approaches are aimed to increase the security issue in the digital material. Cryptography is a way to secure the digital material, but the data are no longer protected after the decryption. So, the watermarking approach is a complementary security technique to ensure the security of the digital material. The watermark can be extracted any time to prove the ownership of the digital material. However, posterior protection aims to combine two techniques (cryptography and watermarking) to prove the integrity and authenticity of the digital material. In the literature, there are four know classifications of the combined watermarking and cryptography approaches based on the way of applying the techniques. We have illustrated them in section two in details.

Chapter 3: Hybrid Watermaking and Cryptography Techniques Digital Medical Image and Telemedicine Security. Chapter 4

Introduction

In this chapter, we will discuss the definition of telemedicine and medical image, the existing medical systems for storage and transfer (like HIS and PACS), the security characteristics in the medical image. Also, the medical image security applications will be presented.

The research and scientific concerns at the present time are focused to serve and develop the medical sector and make this service available for all. Traditionally, the patient has to visit the physician to get the diagnosis. Sometimes, the physician is too far physically from the patient and the patient's health doesn't allow him/her to move.

However, the main concern in the world is to develop the healthcare quality. The human healthcare is considered as the most important point throughout the world. Information technology has come to get rid of these problems and to contribute in the medical service improvement that is provided to people.

Telemedicine is the use of information and communications techniques to offer the health care where the patients and the physicians are disjointed by physical distance. The word telemedicine is a word combined from the prefix 'tele' derived from the Greek and it means the distance, which means telemedicine is a medicine in the distance. The modern health care system like Hospital Information System (HIS) and Picture Archiving and Communication System (PACS) provide the health sector with the digital medical information in easy and fast ways. Ledley is one of the famous researchers who employed the digital computer for the medical goals [Ledley 90]. In the united states in the 1950s, Ledley provided computer applications for dental projects at National Bureau of Standards. He conducted many projects to provide the medical sector with a high capability using computer applications, like Standard Eastern Automatic Computer (SEAC). One of the leading expert system was MYCIN, a system for computer based medical consultation application, which was implemented by Stanford University in 1976.

Digital image

A

Digital medical image

The normal method to generate digital medical image is to capture the image on X-ray films or radiographs, computed radiography (CR), and digital radiography (DR) techniques [Huang 11 (a)].

Medical imaging examinations include computed tomography (CT), X-ray computed tomography (XCT), nuclear medicine (NM), positron emission tomography (PET), single photon emission computed tomography (SPECT), ultrasonography (US), magnetic resonance imaging (MRI), digital fluorography (DF), and digital subtraction angiography (DSA) [Huang 11 (a)].

Picture archiving and communication system (PACS)

PACS is considered as the server of the medical images. It receives and archives images from devices such as Hospital Information System (HIS) and Radiology Information System (RIS). PACS are taken into account the different radiological imaging modalities, including patient data, study support information about the patient, a description of the patient case. PACS consists of two components: database server and archiving system.

After the examinations images are done, the HIS and RIS send the examinations image to the PACS server. The PACS extracts the descriptive information from the DICOM header. Then, update the database system and limit the target of the newly generated data. In the case of a huge amount of data, PACS compress them and store or update the database system.

PACS can be integrated with the Teleradiology system in the medical field. It can support the clinic with the necessary data about the patient. At the same time, it is used as a server containing the database for the hospital medical images. PACS can import medical image from the outside imaging center, then PACS sends the reports to the HIS and other medical expert system of the hospital. Also, the image center can send it to the expert system as in the Teleradiology model.

Moreover, PACS has many advantages regarding to Telemedicine sector. In case of PACS server down, imaging devices can send the images directly to the destination. However, PACS is less risk of losing the image data, because PACS considers multi copies broadcast distribution. Furthermore, the destinations of PACS have local storages, these storages keep the historical data for time, it means the data is still available for a longer time at the system. Another advantage of PACS is that it allows to modify the header of a DICOM image which has been stored in the system. Also, PACS is less liable for any modification of the network performance. [Huang 11 (b)].

Telemedicine

Telemedicine is the delivery of health care using telecommunication, computer and information technology, which includes medical images. Using only one part of the previous components does not consider Telemedicine. For example, using a telephone conversation would not be considered as telemedicine because of the absence of computer and information technology [ ATA 13].

Telemedicine can serve three models in the medical field: telediagnosis (store and forward), teleconsultation (just in time) and telemanagement (real time). In telediagnosis model, the patient examination and images are done by the referring physician site, while the results and images are transmitted to the professional physician side to get the diagnosis and treatments about the case.

There is a delay in the time in this scenario. The second model is teleconsultation, the referring physician site sends the results and the examination of the patient to the professional physician site to get the diagnosis and treatments about the case, while the patient is still awaiting the results. The third model is telemanagement, the professional physician site is connected with the patient in the examination room, and the medical management care is immediate. In this case, the patient will get Then, transmitting the data using telecommunication system. Meanwhile, at the expert side, the computer to display the received information is required. All the patient information has to meet the requirements of the hospital information system (HIS) or clinical management system (CMS), these requirements include data format and real time constraints. [Huang 11 (c)].

Teleradiology is more close to PACS functions in technology terms. But PACS deals with the DICOM image using the LAN network, while teleradiology uses the WAN network. Moreover, if the data is huge, the PACS will compress it in the system. But the teleradialogy is compressing the data even if it is not huge to achieve high speed and low cost using the WAN through the transmission [Huang 11 (c)].

Teleradiology can capture the image and digitize it in a high quality, reformatting the data to be in standard medical image formatting (DICOM), transmitting the image, reporting, storage and display the medical image [Huang 11 (c)].

Digital imaging and communication in medicine (DICOM)

The integration of different digital products, modalities, archiving and information medical systems ]. These security profiles treat the attributes using, associations' security, objects authentication and file security. The next section presents these security profiles in detail.

Secure use profiles

Secure use profiles provide a guide to use the attributes and other security profiles in a certain mode.

The profiles include the safe use of online electronic storage, bit maintaining and electronic signatures.

Secure transport connection profiles

These profiles specialize in the technique used in DICOM applications in order to establish a secure data exchange over a network and internet. Secure transport connection protects the information during the transmission. These profiles are similar to the secure socket layer (SSL), SSL is used in the security of the online web site. Secure transport connection profiles are an application of the asymmetric cryptography. So, the message sent can be read by the receiver and no one else can decode it. In these profiles, there are two opportunities to implement secure transport connection over:

transport layer security (TLS) and integrated secure communication layer (ISCL). The profiles provide DICOM with restricted features that are mandatory for implementation.

Digital signature profiles

Digital signature profiles support tools for the integrity checks using digital signatures. Digital signature lets validation of the identity structure, which is generated, approved or altered a DICOM data. The digital signature generator has to identify the DICOM data set, then calculate the MAC and the hash value. After that, embed the MAC value into the digital signature. While the receiver can verify the authenticity and integrity of the received data by recalculating the MAC value and compare it with the embedded MAC value. The profiles provide three potential ways of digital signature implementation (base, creator and authentication), depending on the content that will be embedded into DICOM.

Media security profiles

The media security profiles support a secure tool to protect the DICOM data against unauthorized access of the information. The profile defines a structure of the DICOM protection exchanging by compressing the data with a cryptographic wrapper. These security way is considered as an application of the asymmetric cryptography techniques.

These security profiles allow encrypting the image using the DES, DSA and other exciting encryption techniques. Whereas, the information after decrypting will not be protected. So, it is difficult to verify [Bouslimi 12 (b)]. Also, the DICOM security standard does icity and reliability its integrity, authent not preserve the confidentiality and integrity of the medical image data. Whereas, its header can be ng is a solution to ensure easily removed and regenerate a fake header by the attacker. So, watermarki and transmission. This way it can provide a standing guarantee the image security through the storage o increase the medical image , t of confidentiality and integrity of the data [Huang 11 (d)]. Moreover and cryptography techniques are applied to medical data. The general security, the watermarking illustration of the encryption and embedding methods are applied at the sender side as follows:

-Image preprocessing: to segment and extract the relevant patient information from the DICOM header.

-Data encryption: to encrypt the medical data and produce ciphered data form.

-Data embedding: to embed the secret information in the medical data.

Where extraction and decryption process are applied at the receiver side, these steps are:

-Extracting the secret information from the received medical data.

-Decrypting the medical data.

-Ensuring the received data integrity, authenticity and confidentiality.

Medical image security requirements

Medial image security is required by the health insurance portability and accountability act (HIPAA) to guarantee that the patient information privacy are protected [Act 96]. DICOM standard provides an optional guide for medical image production. However, in telemedicine, the medical image transmits between the referring site and expert site using the network. The security term becomes very important and critical issue is not just for storing the data in the medical system, but also during the transmitting operation over the network in telemedicine. That is to keep the patients' information in term of privacy, authenticity and integrity security characterization. These characterizations can be described as follows: Confidentiality means rejection of access to the patient information by unauthorized users. While the integrity refers to medical image safety through the transmitting from any tampering, changing or modifying. Moreover, the authenticity is to validate the image source and the image belongs to the correct patient [Bouslimi 12 (a)].

A lot of work is done in this field in order to achieve the highest security level of patient information, medical image and other information related to the patient. In the next section, The characteristics of the medical image confidentiality, integrity and authenticity are discussed.

Medical image confidentiality

The confidentiality means the authorized users can access, modify, or do any other allowed process at the patient information, while preventing the unauthorized user from the access to them or from the editing. It is considered the first step to guarantee the security issue of the patient information privacy [Al-Haj 14].

The Patient information has to stand up the law and ethics requirement of confidentiality. The information must have the critical and important quality of confidence about it. Moreover, the confidentiality of the information must be guaranteed during the transition. Also, The information using must keep the patient information security inside the responsible team like the physician, the lab worker and so on [Abbing 14].

There are two allowed reasons of public law for breaking confidentiality: the first situation, if the patient is accepted to reveal his/her information. The second situation, if it will improve and serve the public health sector [Klutas 77].

Medical image integrity

A code of ethics for health Informatics Professionals (HIPs) has provided us with the guidance and the principles of the health information protection [IMIA]. One of the critical and important point is the integrity. The patient information integrity means the data is intact from any intentional or unintentional modifying from unauthorized person. So, if an attack is happening from an unauthorized person, the person in charge of the medical information in the telemedicine system has to detect that.

Medical image authentication

Medical image authentication aims to identify the image source, the ownership and it is an origin as sending from the source. Which means there is no falsification happening through the transmitting process? The Medical image authentication is used to improve the tamper detection and tamper recovery. The authentication and the integrity are very close together [Al-Haj 14].

The general scenario to the medical image authentication is inserting data from the source side in the cover host image. Then send these images to the receiver. At the receiver side, the receiver has to extract the embedded data in the host image and verify if it is authenticated or not.

The medical image authentication schemes can be classified into: A digital signature (meta data) based and watermarking based. In the digital signature, the header data or physician digital signature that is stored along with the medical image is used to verify the data authenticity [

Medical image security applications

Many works in the medical image watermarking and cryptography techniques for security issue are proposed in the literature. We have presented in this section the most significant and important approaches of the watermarking and cryptography applications in the medical sector. Some of them presented the watermarking approaches in the frequency domain, while there are many works in the spatial domain. Based on previous studies, the frequency domain is better than the spatial domain in robustness security issue. But, spatial domain is better than the frequency domain in the complexity issue. Since we work with the real time applications (Telemedicine), our contribution focus in the spatial domain for less complexity goal, and improvement of the compromise between robustness, capacity and imperceptibility requirements.

In this section, we divided the existing security applications in the medical sector into two categories.

The first category is the pure watermarking techniques that are applied in the frequency and spatial domains. While the second category is the medical image application based on cryptography and watermarking techniques.

Pure watermarking applications in the medical image

In [ Kannammal 11], the authors presented multiple and fragile image watermarking of DICOM medical image based on Haar-DWT frequency domain of four levels. The approach addressed the problem of the source authentication, the medical information authentication and transmission of patient analysis details. Multiple watermarks are also used: the reference watermark, Tamper Assessment Factor (TAF), and physician's signature. When using the Haar wavelet technique, the authenticity was satisfied against some kind of attacks, but for other attacks such as rotation and cropping, contrast, flip, blurring, sharpening, salt and pepper noise, and Gaussian noise, we note a remarkable loss of the embedded data.

Another watermarking approach in the frequency domain is presented in [Fakhari 11]. A new and robust technique is proposed for medical image. The approach aimed to protect the copyright of the content and ensure the authenticity of the patient information. It consists to divide the image into three wavelet transform by using a graph theory approach to find optimal places to embed the watermark key. The algorithm ensures a good invisibility and robustness, especially against LSB attacks and is reliable enough for tracing the intruder.

In [ Dong 12], The authors presented a zero watermarking blind technique using both DWT and DCT in order to enhance the robustness against common and geometric attacks and the invisibility of watermark. Also, the approach aimed to provide a confidential and integrity (privacy) security issues of the medical information through the transmission between the hospitals. The technique had improved the process of choice of regions of interest (ROI). The embedding process consists to apply Arnold transform to the binary watermarking image, then decompose the image into one layer DWT, after that compute the DCT for the whole LL part to get featured vector. The lowest frequency in feature vector is chosen and one gets the sign sequence. The experimental result shows a good robustness against different attacks and high weakness when applying JPEG compression and Median Filter attacks.

[ Coatrieux 13] proposed a medical image system to verify the image integrity. The system extracts the signature information from the ROI or from the pixel blocks of the Region of Interest (ROI). Then, the extracted signature is embedded in the no significant part of the image Region of Non Interest (RONI). At the verification side, the extracted signature is compared with the recomputed signature at the three level protection L1, L2 and L3. For each integrity level, there is an independent and specific signature. The level one is focused on the detection, while the level two is imported in the localization, and the level three are focused on the approximation of the image degradation. The system has limited with some kinds of degradation and alteration like compression, filtering, rotation, and brightness. But it did not cover the other kinds of attacks. It is not global over all the images tampering.

In [Li 12], the authors presented a blind zero watermarking approach in the frequency domain. The approach is applied in the medical image and based on Discrete Cosine Transform (DCT). The scheme is merging the visual feature vector with encryption technique. Firstly, DCT technique is applied to the medical image and 9 th lowest frequency coefficients are chosen. After that, obtained the sign sequence of low frequency coefficients. By using the watermark information and the feature vector, they compute the key sequence based on the HASH function cryptography. The algorithm is given a full consideration of the visual properties of the watermark embedding, which means a low degradation in the watermarked image. The approach provides acceptable capacity and low in complexity. Also, it has a strong robustness against cropping and scaling attacks. But, the quality of the extracted watermark image is very low after noise, compressions, rotation, rotation and translation attacks. image integrity. The proposed technique provided robust reliability for medical image without any degradation in its quality. The encrypted data frame is similar to the original data frame. Also, the technique has to be improved in order to shrink the time required to encrypt and decrypt huge images.

In [Bouslimi 12 (a)], the authors presented a joint encryption and watermarking approach. The approach aimed to verify the integrity and authenticity of the medical image in the spatial domain as well as in the encrypted domain during the transmission and storage. The technique is based on the quantization index modulation (QIM) with encryption algorithm, encryption algorithm can be a stream cipher RC4 or a block cipher AES. The approach conducted two main processes: protection and verification. Protection phase consists in the watermarking and encryption of the medical image.

It embedded two messages by using two keys. Each message contains a security information called authenticity code (AC) which proves the image originality and integrity. In the verification phase, one message has to be extracted from the watermarked image using one key, while the other message has to be decrypted from the encrypted image using the second key. The reliability decision is conducted based on the two messages reliability. The performance evaluation of the Peak Signal to Noise Ratio (PSNR) achieved is around 49 dB without applying attacks. The experimental result shows that the quality is acceptable and the capacity is sufficient for embedding. Similar work is presented in [Bouslimi 12 (b)]. The authors combined the RC4 stream cipher and two replacements watermarking variations: Least Significant Bit approach and the Quantization Index Modulation.

A hybrid watermarking and encryption algorithm is also presented in [Kannammal 14]. The watermarking technique is performed based on symmetric matrix to build the new non-tensor product wavelet filter banks, where it provides the capability to disclose the singularity in several situations. While the encryption is performed based on three encryption techniques RSA, AES and RC4. The original image is natural image and the medical image is the watermark image. After one level wavelet decomposition, the medical image is embedded in the low high sub-band coefficient of the original image. The embedding is done by using least significant bit approach, then inverse decomposition is done to obtain the watermarked image. The watermarked image is encrypted by using RSA, AES and RC4. At the decryption/ extraction phase, the encrypted watermarked image is decrypted using RSA, AES and RC4 in order to obtain the watermarked image, then, wavelet decomposition one level is applied to the watermarked image to get the four sub-bands (LL, LH, HL and HH). The LH sub-band is considered to extract the embedded watermark image, and inverse LSB is applied to obtain the medical image (watermark). The scheme applied three different cryptography techniques with the watermarking technique. The encryption / decryption time was less for RC4 than for AES and RSA. Also, the performance and speed of RC4 were better than AES and RSA. The correlation value was around 1 for AES and RSA while it was around 0.9 for RC4, which means the image quality by using AES and RSA is better than by using RC4. The PSNR values were better by applying RC4 than AES and RSA (lossless). The approach has the ability to resist to different attacks like noise, rotation, contrast and brightness attacks, where the PSNR was around 91 dB after different attacks.

The authors in [Al-Haj 15 (a)] proposed cryptography algorithm and digital signature approach in order to prove the confidentiality, authenticity and integrity of the pixel data medical image as well as for the header. The cryptographic key and the signature are created from the header and pixel data, which has established a strong connection between the medical image data and security data applied in the algorithm. The scheme is based on asymmetric and symmetric data encryption to offer the confidentiality, integrity and authenticity of DICOM's header and pixel data. To attain the confidentiality, the pixel is encrypted, while the authenticity and integrity is attained by applying the digital signature. The approach is considered as two processes: encryption and signature generating process, decryption and confirmation process. At the encryption and signature generation process, the header and data pixel are encrypted using hash function and the output is divided into two parts. First part is used as encryption key while the second part is used as the initialization vector. The encryption key and the initialization vector are used to encrypt the confidential attributes of the header and data pixel based on AES-GCM. Then, by using CDSA, embedding the authentication tag of the header with the private key of the sending object and save the result as a digital signature in the header. The approach is robust against statistical attacks and it achieved acceptable encryption and decryption time performance (low in encryption and decryption time). But, the entropy was around 7 bits/pixel, also,

The PSNR was around 11 dB.

A lot of techniques merging watermarking and cryptography are proposed in previous studies. We have presented some of them. Other works can be found in [Bouslimi 15], [Guo 15] and [Al-Haj 15 (b)].

Conclusion

The medical image is one of the most important elements in the telemedicine and the health care sector. Therefore the security of medical image is very important to prevent the intentional or unintentional distortion. Meanwhile, the confidentiality, the authenticity and the integrity are working together. You cannot separate one from the others and each one depends on the others. In the literate review, there are two ways to obtain the security of medical images: watermarking and meta data (digital signature). Encryption technique can also be used to increase the security level.

DICOM security profiles allow encrypting the image using the DES, DSA and other exciting encryption techniques in the DICOM header. Whereas, the information after decrypting will not be protected. So, it is difficult to verify its integrity, authenticity and reliability. Also, the DICOM security standard does not preserve the confidentiality and integrity of the medical image data. Where, its header can be easily removed and a fake header can be regenerated by an attacker. So, watermarking is a solution to ensure the image security through the storage and transmission. This way it can provide a standard guarantee of confidentiality and integrity of the data. The current watermarking existing solutions do not provide efficient techniques to cover the confidentiality, integrity and authenticity of the digital medical data. Moreover, the existing approaches do not offer a good compromise between the watermarking requirements (robustness, imperceptibility and capacity) as well as complexity, since we work with real time applications (telemedicine).

Our work aims at filling some of the gaps of the previous solutions and to ensure the security of the medical image during the transmission and storing by providing watermarking solutions with better compromise between the watermarking requirements and cryptography solutions ensuring symmetric key security with less complexity.

.

SECOND PART

Our contributions are presented in this part. Chapter 5 includes pure watermarking approaches in the spatial and frequency domain, while chapter 6 presents a pure cryptographic approach. Also, we present a hybrid cryptographic and watermarking approach in chapter 7. All of these contributions are published in international journals or conferences.

In chapter 5, we aim at providing watermarking solutions to meet the real time requirements of telemedicine, namely execution time and memory space constraints. As we mentioned in the first part, robustness is another critical issue in telemedicine. Based on the previous studies, the frequency domain is better than the spatial domain in robustness security issue. The spatial domain is better than the frequency domain in the complexity issue. To meet real time constraints (less complexity as far as execution time and memory space are concerned) and improve the barter between robustness, capacity and imperceptibility, we have proposed the following solutions:

• An approach based on FCA which provides the way to find a distribution of the embedding area in order to improve the robustness and imperceptiblity. The payload of the watermark is not that large since it is generated from the header information of the DICOM image.

Moreover, the complexity of our approach is not huge.

• An approach based on ZBDD. We investigate the way to generate adaptive and informed watermark based on ZBDD rules, which has an impact on the storage space.

• An approach based on Weber's law which provides high robustness. Indeed, it generates informed watermark based on Weber differential excitation and the informed watermark gives the ability to detect the tampered zones.

• An approach in frequency domain based on DWT. It provides more robustness, high imperceptiblity as well as low complexity in comparison to existing approaches.

We can summarize the achieved goals of our work in watermarking part as follows: In combined watermarking and cryptography part (chapter 7), we are aiming to increase the security level of the digital material by taking the advantages of the two techniques with high concentration about complexity and reversibility aspect.

Watermarking approaches Chapter 5 5.1 Introduction

In this chapter, we will present our contributions in watertermarking domain. These solutions aim at meeting real time constraints (less complexity as far as execution time and memory space are concerned) and improving the barter between robustness, capacity and imperceptibility in telemedicine. The remaining of the chapter is organized as follows.

In the second section, we present our approach based on formal concept analysis to improve robustness of medical image watermarking scheme in the spatial domain. The third section deals with our watermarking approach which generates an optimal informed and adaptive watermark image based on Zero-Suppressed Binary Decision Diagram for medical images. The fourth section is dedicated to novel robust informed watermarking approach and tamper detection based on Weber Differential Excitation descriptor. The approaches presented in section 5.2, 5.3 and 5.4 are watermarking approaches in spatial domain. The last section presents a novel watermarking approach in the frequency domain, namely CT scan images watermarking scheme in DWT transform coefficient.

Formal Concept Analysis to Improve Robustness on Medical Image Watermarking Scheme in the Spatial Domain.

In this section (5.2), we present a novel robust approach for medical image watermarking in the spatial domain based on the Formal Concepts Analysis (FCA) model [ Ganter 12]. The FCA allows us to find an optimal insertion position in the non-region of interest (NROI) of medical images. We extract the watermark information from the header of medical image information (IODs). The watermark information is defined by Patient Name, Patient Date Of Birth, Patient Age and File Modified Date information. There are relations between these types of watermark information that can help us to know if any (cutting, adding, replacing) attacks have happened (Tamper Detection).

Our experimental results show that we extract the embedded watermark image with high quality, low payload and low computational complexity from the attacked watermarked image after attack scenarios. This part is organized as follows: in the second section, we present the FCA model, definitions and domains of application. The third section is dedicated to the proposed approach (embedding and extraction phase). Fourth section shows the experimental results (robustness, capacity, and complexity and tamper detection). The conclusion is presented in the fifth section.

Formal concept analysis (FCA)

FCA was initially developed in data analysis, knowledge representation and knowledge discovery in databases (KDD) [ Alqadah 11]. The FCA can provide a support for processing large dynamic, complex data sets with additional knowledge. It is a sub field of applied mathematics based on the lattice theory. Starting from a formal context built by a set of objects that share a number of properties, this method returns a lattice with a special property, the Galois property. The objects, and the properties which are also called attributes, can be more or less abstract depending on the type of application. In different applications, the appropriate choice of the context allows to obtain more information from the lattice. The FCA has been applied in various fields such as data mining, conceptual modelling, social networks and the semantic web [ Alqadah 11] and [Wille 92]. For FCA in ontology engineering, the paper of Richard [Richards 97] was the first paper using FCA in combination with ripple-down rules to extract ontological vocabulary from knowledge bases. FCA played the role of a tool for ripple down rules (RDR), performing the derivation of concepts and the relation between them. The authors in [Jiang 03] combined FCA with natural language processing for building ontology in the field of cardiovascular medicine. In our paper, this theory is applied with an appropriate choice of objects and attributes in order to determine the region of encryption of the watermark. Let us do a short presentation of the FCA. all the attributes in the Intent fall under all objects in Extent.

FCA definition

Sub-concept relation, Super-concept relation

The concept (A1, B1) is a sub-concept of the concept FCA can be illustrated more clearly through an example. Let us suppose we have records for a set of images. For each image, there is a set of its features. We note the features (M), M = {1,…., 8}, as shown as follows:

(A2, B2) if or . So (A2, B2)
Chapter 5: Watermarking Approaches 92

Objects(G)\Attributes(M) A B C D E F G H 1 ü ü ü ü 2 ü ü ü ü 3 ü ü ü 4 ü ü ü ü 5 ü ü ü ü 6 ü ü ü 7 ü ü ü 8 ü 9 ü ü ü ü 10 ü 11 ü ü ü ü 12 ü ü ü ü

H YCbCr

The images and their features : 1 . 5 Table Table 5

.3: Formal concepts of data given by the images and their features

In table 5.1, we have 12 images (G), G= {1,….., 12}. Our example describes the images and their features in 12×8 binary matrix I (table 5.2). In the following, C refers to a concept, and A and B are extent and intent, respectively. In table 5.2, the first formal concept, C0, contains zero object (extent) with all attributes (intent), which means no image contained all the descriptions. For the second formal concept, C1, the images 1, 5, 9 and 11 contain features 1,2,3,5. In the last concept, C8, it means that there is no feature contained in all the images from 1 to 12. The first concept includes zero object with all attributes and the next concept includes the sharing objects with their attributes and so on to the last concept. We denote the extent is increasing and the intent is decreasing until the intent is empty intent= (Incrementing way). In the same way, if we take a look at the concepts from C0 to C8, we note that the concept C8 includes all its extent (objects) with empty intent (attributes) and that the previous (C7) concept decreases the extent and increases the intent until the extent becomes the empty set extent= (Decrementing way). Figure 3 illustrates the lattice called also formal concept analysis line diagram between the images and the features they contain. applied FCA to analyze diseases, treatments and symptoms to find implications and relationship hidden in the data, FCA applied to be expert system in medicine.

For ontology engineering based FCA, the paper [Richards 97] was the first one to use. FCA in combination with a ripple down rules to extract ontological vocabulary from knowledge bases. FCA played as a tool into ripple down rules (RDR) and supported the derivation of concepts and the relation between them. In [Jiang 03], we can find a combination of FCA with natural language processing for building ontology in the cardiovascular medical domain.

We apply the FCA principle in the watermarking techniques to determine an optimal position of embedding, in order to obtain low complexity, low capacity, high robustness and high imperceptibility for the embedding and the extraction process. The optimality is considered here according to watermarking requirements.

The proposed approach

Embedding phase

Figure 5.2 illustrates the watermark embedding scheme. Our embedding steps can be summarized by the following: Modified Date (FMD) in the fourth watermark (w 4 ), as illustrated in the algorithm I. We have chosen these four watermark information from IOD's because there is a relation between them and, then, we can verify if the relation is kept. In our approach we calculated, from FMD and PDOB, the age and we compared the result with the watermark age.

The building of the watermark from the DICOM header can be summarized as follows: The extraction of the four regions of i, the building of the FCA lattice and the generation of the FCA matrix for each region are done as follows: We used the original image in 512 × 512 sizes. Figure 6.6 illustrates the original image and the watermarked images for two different values of factor t. As we can see in this figure, when t is close to 1 the watermark is invisible and there is no degradation in the image quality (figure 5.6, (b)), but if the t is close to 0 the watermark is visible and there is a little degradation in the image quality, as we can see in figure 5.6, (c).

Algorithm

Algorithm

Extraction phase

In the extraction phase (algorithm IV), the matrix positions that are extracted from a Boolean matrix based on FCA are required (LUpos, LDpos, RUpos, RDpos). Then the extraction done by using the linear interpolations is as follows:

(5.8)

(5.9)

(5.10) A Attacked watermarked image with t = 0. 98 B Retrieved the attacked watermark images with t = 0.98

Robustness

Table 5.4 shows the PSNR values for extracted watermarks from an attacked watermarked image after geometric and non-geometric attacks made with Stirmark, compared with the original watermark. We compared our results with the proposed methods in [[ Li 12], [ Tsai 12] and [ Miao 12]. Our proposed scheme outperforms the algorithms introduced in [Li 12], [ Tsai 12] and [ Miao 12].

In order to further verify the robustness under image processing operations, we added Gaussian, salt and pepper noise, JPEG compression with quality factors 60 and 90, and image filtering as 3 × 3 and 5 × 5, used in methods [ Su 13], [ Li 12], and [ Miao 12]. Table 5.5 lists the results of adding noise, which means that our proposed algorithm has stronger robustness. The metric used to measure the quality is a Normalized Cross Correlation (NCC). From the above results in tables 5.4 and 5.5, we can conclude that our proposed method has a stronger robustness against geometric, non-geometric and common image processing attacks.

Capacity

Our watermark consists of four watermark images. After applying various attacks as we see in figure 5.8, we can retrieve the watermark. Even though there are degradations in the watermark image quality, we still have the possibility to retrieve the watermark. Our approach provides a low capacity. This is because the watermark that is embedded is very small in terms of size compared with the original image size and in comparison with the works in [ Su 13] [ Li 12] [ Miao 12], as we can see in

Complexity

In terms of measuring the complexity with the proposed approach, we calculated the execution time for the embedding and extraction process using MATLAB 7.14 with a CPU of 2.4 GHz and 2 GB RAM. Our proposed approach has a lower complexity than [ Su 13]. Table 5.7 shows the execution time for embedding and extraction processes for our proposed methods and those of [ Su 13].

Tamper detection

Our approach makes it possible to detect if there have been removal attacks or the addition of any new watermarks. By subtracting the fourth watermark from the second watermark, our approach gives us the third watermark. By comparing the subtraction result with the third watermark, we can know if

Watermark size

Proposed Approach 200 Total = 880 bits 312 152 216 [ Su 13] 4096

[ Li 12] 1056

[ Miao 12] 1024 Of Birth), the result should be the patient age, this value is equal to .

FCA conclusion

We presented a reversible novel watermarking approach in the spatial domain. Our approach is innovative and based on using Formal Concept Analysis. Its main feature is that it generates the optimal position for embedding. The watermark is built from some header information of the DICOM image. It is embedded into the NROI of the medical image. Based on experimental results, our approach demonstrates a lower computational complexity, using low capacity for the watermark and has a high robustness. Moreover, the approach can detect the removal and/or addition and/or replacement during attacks, which would be useful for tamper detection issues. Although the proposed approach has been limited in this approach to medical image, it could be used with other kinds of images.

Moreover, our FCA approach has the ability to detect the attacks by comparing the extracted concepts from the watermarked image after attacks with the original concepts from the original image.

However, FCA provided a distribution embedding area, which makes the imperceptibility is high.

Generating Optimal Informed and Adaptive Watermark Image Based on Zero Suppresed Binary Decision Diagram

Watermarks generation manner is one of the most important aspects in watermarking schemes, and should aim to produce as small watermark as possible (low data quantity to be embedded in the multimedia) to decrease the complexity of computational processes. Although embedding a large amount of watermark data in almost all different media increases the chances of recovering it, this also increases the complexity, which can become impractical for real time applications. In this approach, we focus on the robustness of medical image watermarks and present the means to generate a small watermark. This idea is very innovative in the watermarking field. The proposed approach is based on Zero-Suppressed Binary Decision Diagrams (ZBDD) [Minato 01]. ZBDD has proven its effectiveness in many fields, such as data mining, big data processing, computer networks, etc.

Application of ZBDD to medical image watermarking will help us to take into account not only the complexity and the capacity factors but also the watermark robustness.

An optimized watermarking algorithm should have a minimum of calculation with a high robustness requirements. Such algorithms are useful for real time applications. The importance of capacity lies in not increasing the size of the original image with the addition of the watermark. The overall size of the watermarked image should be limited by embedding watermark data that are small and efficiently

robust. An invisible watermark plays an important role in increasing the robustness. So a robust watermark can be extracted perfectly after exposure to attacks.

It should be noted that until now, there has been no robust watermark algorithm which resists attacks when hiding data [Laouamer 13] [Tsougenis 14]. Generally, in order to have more chances to recover the watermark, we need to hide a greater quantity of data [ Shahid 12]. Also, another important point is how a watermark is generated. The watermark generated in a single, fixed operation and does not necessarily suit a large variety of different situations. Such generation process is a non-dynamic generation process. The fixed watermark obliges enough capacity.

In this approach, we proposed a solution regarding the problem of watermark generation and quantity of data to be dynamically embedded. The proposed approach, which we consider to be highly innovative and original in the field of watermarking, is based on Zero-Suppressed Binary Decision Diagrams (ZBDD). The ZBDD model is known to reduce the large-scale of data by removing the unimportant part. Moreover, the main idea of the proposed algorithm is to build an optimized watermark based on image features, which we call an informed watermark. The ZBDD procedure is used to obtain the highest value pixels, which give the watermark its characteristics. We have tested the robustness of our solution against many kinds of geometric and non-geometric attacks.

This part is organized as follows: Second section presents the binary decision diagram, ordinary binary decision diagram and zero suppressed binary decision diagram principles. Section three presents the proposed approach. Section four is dedicated to the experimental results. A comparative study is presented in section five. The chapter ends by the conclusion and discussions.

Binary decision diagram (BDD)

BDD is a way to represent Boolean functions. Representation by BDD was inspired by the Shannon representation [Shannon 38] for Boolean functions. This representation makes it possible, for a fixed i, to rewrite the function as:

where is the value of the function when x i =1, is the value of the function when

x i =0, and the symbols (union) and (intersection) from classical set theory stand respectively for the symbols from formal logic and lattice theory.

BDDs can represent large datasets in an efficient way for functions and are becoming the most popular choice for Boolean functions representation [ Günther 02]. It is easier to understand binary decision diagrams with an example, as illustrated in table 5.8, and figures 5.9 and 5.10. In this graph, the x 3 variable refers to x 2 by one of two values: one or zero. Then, every x 2 value refers, in the same way, to an x 1 value to reach the terminals of one or zero. The paths that reach a terminal node with the value 1 are the following:

x 1 x 2 x 3 F 0 0 0 0 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 0 1 0 1 1 1 1 0 0 1 1 1 1 (0) 1 1 0 1 T 0 T 0 a 0 a 1 0 [x3] [x2] [x2] [x1] [x1] [x1] [x1] 0 T 1 T (0) (1) (0) (1) (1) (1) (1) 1 T 1 0 a
In the binary tree graph, some of the paths or some of their sub-paths will be found to be inefficient.

The BDD reduces the representation of the binary tree graph as illustrated in figure 5.10, by eliminating unnecessary sub-paths. The BDD representation has two terminals, a 0 terminal and a 1 terminal. The nodes have two edges, the 0 edges and the 1 edges. All the possible combinations in the set will be represented by paths called "1 paths" if the terminal node is one, or "0 paths" if the terminal node is zero, as shown in figure 5.11 [Tzoref- Brill 13].

(1)

1 T 0 m 1 0 [x 3 ] [x 2 ] doi: 0 T 1 (0) [x 1 ]

Ordinary binary decision diagram (OBDD)

Ordinary Binary Decision Diagram (OBDD) is a structure which transforms a BDD into a more compact graph representing the same Boolean function, thus reducing the size of the graph. Unlike standard BDD, OBDD representation is unique in the sense that it does not depend on the variable order. OBDD can significantly enhance the graph representation by keeping the data volume small and thus using only a small amount of memory. The principle of OBDD is to delete duplicate nodes of a binary decision diagram that have no high value for large-scale data. OBDD is based on two reduction rules, the first of which consists of deleting duplicate node that refers to the same following node. graph. The second rule is to combine equivalent sub-graphs, as shown in Figure 5.12(b). The x node on the left side points to f 1 if the value is one, and to f 0 if the value is zero. In both these cases of x, we can reduce the representation by removing one x node [Kurai 07].

Zero-Suppressed binary decision diagrams (ZBDD)

Figure 5.13 shows a Zero-Suppressed BDD (ZBDD) [ Shahid 12] and [Shannon 38] for a given Boolean function and illustrates how a binary decision diagram is reduced in order to obtain a ZBDD.

The nodes from which both branches point directly at the terminal node 0 are removed. Figure 5.14 gives an example of node elimination whose full arc points to 0. Figure 5.13 (a) gives graph to be reduced and Figure 5.13 (b) gives the fully reduced graph. This representation is more convenient and concise than OBDD, particularly for some applications based on the combination set bits. So ZBDD are widely used for large-scale combination set data and deal with reduction rules that are explained in the ordinary BDD. In ZBDD, it is the combination between the inputs rather than their number that is important. We can apply logic operations for the combination set in the graph, such as union, difference, product, etc.

∩ (Intersection) × (Product) 0 0 0 X 2 1 1 1 X 1 X 3 (0) (0) (1) (0) 0 0 X 2 1 1 X 1 (0) (1) (0)
Table 5.10 describes the combination sets, their frequencies in the original image i, and their binary representation. In Table 6.3, we have to remove those combinations for which the frequency is equal to zero, such as {CEH, ACG, CEGH, ACGH, ACEH, ACEGH}. The symbol f 0 represents the least significant bit, f 1 represents the second least bit and so on until f 7, which represents the most significant bit.

5-Build the ZBDD Map for the result from the previous step for each combination set as illustrated in figure 5.14. 6-Find the ZBDD vector for the item set histogram as follows:

f 7 ={}, f 6 ={CE}, f 5 ={}, f 4 ={AC}, f 3 ={CH,CE,AC,CEG,ACH}, f 2 ={CH,CE,ACH,ACE}, f 1 ={CG,CE,ACE}, f 0 ={CH,CG,CE,AC,CGH,ACH,ACEG} H G F E D C B A A A E D C B A A B A f 0 f 1 f 2 f 3 f 4 f 5 f 6 f 7 0 1
7-Apply ZBDD rules. Based on the ZBDD reduction and sharing rules, we can note some paths are included in other paths, such as the combination CH represented in f 3, which should be involved in path ACH. So, after applying ZBDD, we can obtain the paths illustrated as follows:

• Remove f 7 , f 5 // because the combination sets have frequencies equal to zero • In f 3 , because CH is included in ACH, remove CH; because CE is included in CEG, remove CE; because AC is included in ACH, remove AC. // intersection and union rules The size of the watermark (the amount of text to be embedded) depends on the choice of combination and its number of occurrences (frequency). For example, choosing a watermark in the case of f 2 :

• In f 2 , because CH is included in ACH, remove CH; because CE is included in ACE, remove CE • In f 1 , because CE is included in ACE, remove CE. • In f 0 , because CH is included in ACH, remove CH; Finally: f 7, f 5 = f 6 = {CE} f 4 = {AC} f 3 = {ACH, CEG} f 2 = {ACH, ACE} f 1 = {CG, ACE} f 0 = {CGH, ACH, ACEG}
f 0 {CGH, ACH, ACEG} {1*3, 3*13, 4*1=46 } f 1 {CG, ACE} {2*3, 3* 6=24 } f 2 { ACH, ACE} {3*13,3*6=57 } f 3 {ACH, CEG} {3*13, 3*8=63 } f 4 {AC} {2*25=50 } f 5 0 0 f 6 {CE} {2*79= 158 } f 7 0 0 f i = ZBDD
to ROI

Chapter 5: Watermarking Approaches

The watermark embedding algorithm can be presented as follows (Algorithm III):

Watermark extraction

The extraction process for watermark w a (an attacked watermark), after applying an attack, consists in extracting w a from the attacked image i wa . This requires the reverse operation to the embedding process applied to the entire set of combinations selected at the embedding step. We thus extracted watermark w a for each type of attack we tested, which included JPEG, Median filtering, Adding noise and Rotation. We summarize the watermark extraction process in algorithm IV below.

Algorithm IV

Attacks and extracted watermark

To test the robustness of the proposed algorithm, the watermarked image i w was subjected to several types of attack. To do this, we used Stirmark Benchmark; one of the most commonly used benchmark software tools, by making attacks on a given image [ Petitcolas 12]. We chose some examples of the most dangerous attacks, described in table 5.12, and tested our algorithm on several medical images, We noted that for each image type and for each corresponding Boolean function, the original watermark w and the extracted watermark w a are very similar to one another despite the different attacks, indicating that the proposed approach has a high robustness.

In the following section, we measure the degree of similarity between w and wa through some wellknown metrics such as PSNR (Peak Signal Noise Ratio) [Huynh-Thu 08] and correlation coefficient (CC) [ Nakhmani 13] and [ Imamura 11].

Watermarked image quality, watermark robustness and evaluation

To measure the robustness and the imperceptibility of an image watermarking algorithm, several metrics can provide answers. In this part, we are particularly interested in PSNR and CC.

The Boolean functions are used in our tests for all the illustrated images were:

Watermarked image quality

Imperceptibility is defined by the degradation in the watermarked image after embedding. So, a good quality watermarking approach has to preserve the watermarked image quality and it should be similar to the original image. In table 5 The results in table 5.13 show that our watermarked image is of good quality, and that our approach preserves the image from degradation with very high fidelity.

Watermark robustness

In this section, we test the robustness of our approach against different and dangerous attacks. It can be noted that the degrees of similarity between the original watermark w and the extracted ones w a are very high, as can be seen in the results given in tables 5.14, 5.15, 5.16 and 5.17. We explain the results in the case of each metric. For PSNR, it should be noted that all its values for different attacks are beyond 34 dB, which means a strong similarity between w and w a . The CCs are very close to 1, which can be interpreted as a high similarity between w and w a .

Table 5.14: Similarity metrics between w and w a in the case of image "hand" Table 5.15: Similarity metrics between w and w a in the case of image "brain 1" 5.17: Similarity metrics between w and w a in the case of image "leg"

Comparative study

Our comparative study focuses on three aspects: imperceptibility, robustness and capacity.

Imperceptibility

Our comparative study focuses on three aspects: imperceptibility, robustness and capacity.

Imperceptibility was measured using PSNR and compared with the studies in [Tsougenis 14] and [ Shahid 12]. Indeed, those works propose adaptive watermarking approaches whose watermark properties are similar to ours. Table 5.18 shows the average values of PSNR for our approach compared with these previous studies.

Table 5.18: Comparative study of image quality Table 5.18 shows there is a clear difference between our results and those from [Tsougenis 14] and [ Shahid 12], as our image quality is much higher.

Robustness

In order to measure the robustness of our approach, we measured the PSNR and CC between the original watermark image and the attacked extracted watermark images. PSNR values were compared with the results in [Tsougenis 14] and average CC results were compared with those from [Shahid 12], as shown in tables 5.19 and 5.20. As we can note from tables 5.19 and 5.20, our approach obtained a better result than the previous studies in terms of robustness, with PSNR is around 37 dB and CC is around 0.9990

Attacks

Capacity

Capacity should be sufficient for the watermark payload, as is the case in our approach, but should also remain small enough to limit complexity. As shown in table

ZBDD conclusion and discussion

In this approach, we addressed the problem of generating watermarks as small as possible (small payload) to adapt the hidden data to real time applications by maintaining high robustness, high imperceptibility and low complexity within a medical image. We have proposed a novel and optimal approach that is completely innovative through its generation of an intelligent (adaptive) watermark based on ZBDD, a technique which has already proved its usefulness in many applications such as path reduction in wireless networks, production management, etc. An adaptive watermarking method based on Zero-Suppression in ZBDD can generate a watermark with a minimum size while preserving a strong robustness, thus fulfilling the needs mentioned above for low computational complexity and real time applications. We tested our algorithm under several attack scenarios and measured its robustness in the case of invisible watermarking based on linear interpolation. The results obtained show that our techniques represent a new-generation watermarking method offering low complexity, high robustness and imperceptible watermarks. This work compares favorably with the results from other methods in terms of imperceptibility, robustness and capacity.

A Novel Robust Informed Watermarking approach and Tamper Detection Based on Weber Law

In this section, we present our semi blind and informed watermarking approach based on the Weber differential descriptor to build a watermark from the original image in order to achieve high robustness and to detect the tampered zones. We divide the original image into n by m blocks and the centered pixel is chosen to be concerned for watermark embedding in the spatial domain. The tamper detection is proved into tampered watermarked image by comparing the extracted watermark after attacks with the original watermark image. We focused also through this approach on the watermarking robustness and tested it against different scenario of attacks. The experimental results

show the perfect covering of tamper issue and also the watermark robustness.

The structure of this chapter is as follows: the second section presents the Weber law. The third section presents the proposed approach. Section four shows the obtained experimental results, while section five describes the proposed approach for tamper detection. In section six the comparative study and finally the conclusion are presented.

Weber law

Weber law in general describes the relation between quantity and intensity and also how to increase the ratio of the quantity regarding to the intensity. The ratio of the incremental threshold with the background intensity is constant, sometimes called Threshold Versus Intensity (TVI). When the increment threshold is measured on various intensity backgrounds, the threshold increases in the intensity proportion. This relationship is defined in Weber's law [Chen 08], [ Liu 13], [Chen 10]:

(5.12)

where represents the incremental threshold, the initial value of the intensity and is a constant value of the fraction result. The previous fraction is known as Weber fractional as illustrated in figure 5.22. eights neighbors where M1 is the pixel x i-1 and y j-1 , M2 is the pixel x i and y j-1 , M3 is the pixel x i+1 and y j-1 , M4 is the pixel x i+1 and y j , M5 is the pixel x i+1 and y j+1 , M6 is the pixel x i and y j+1 , M7 is the pixel

x i-1 and y j+1 and M8 is the pixel x i-1 and y j : The second Weber descriptor, the Orientation, consists to compute the orientation of the current pixel based on the following interpolation:

M 1 M 8 M 7 M 2 M 0 M 6 M 3 M 4 M 5
(5.14)

Robustness based proposed approach

Through this chapter, we will build our watermark based on the host image information using Weber Differential Excitation descriptor . We divide the image into 3 by 3 overlapping blocks, then we compute the differential excitation for each block. The obtained matrix will be considered as the used watermark (Informed watermark). In the extraction phase, the extractor will extract the attacked watermark from the attacked watermarked image, then compare the original watermark with extracted one and finding the differences between both in order to precise the tampered blocks.

Embedding phase

The watermark embedding process is summarized by the following steps:

1-Divide M X N original image into an F number of 3 X 3 blocks. M and N are the image size, while F is the number of producing blocks.

2-Calculate the Weber differential excitation descriptor for each block using the equation described above.

3-The obtained values (M/3 X N/3) are considered as the informed watermark images w s as we can see in figure 5.25.

4-For each block in the original image, choose the center pixel and embed the intensity of the watermark pixel using the following linear interpolation:

(5.15) where is the watermarked of the block n; is the watermark intensity of the block n and is the center value of the original image of block n, such as .

Extraction phase

In the extraction process and after tampering the watermarked image, we extract the watermark image from tampered watermarked image and we find the tampered blocks as illustrated in the following steps:

1-Divide the M X N watermarked image into an F number of 3 X 3 blocks; M and N are the image size; and F the number of producing blocks.

2-Extract the watermark value for each block of the pixel of the center using the following linear interpolation:

(5.16)

In the equation 5.16, is the extracted block n.

Experimental results

The used gray scale medical images are of size 255 X 255 taken from [DICOM] as shown in figure 5.24 (we take into account that the image size divided by 3, the result is integer output without rest). Based on the value of , we can control the visibility/invisibility of the watermark. We can note from figure 5.26 that when is close to zero, there is degradation in the watermarked image and the watermark become visible. When equal to 0.5, the degradation will be less. Moreover, if is close to one, there is no degradation in the watermarked image and the watermark became invisible, which is the suitable case of our embedding process. We illustrate in figure 5.27 the applied attacks on the watermarked images and we calculated the corresponding PSNR values between the original watermark and the extracted one after each attack. The watermarked image is attacked using Stirmark Benchmark software [ Petitcolas 12]. We note that we achieved a high robustness through the PSNR values which exceeds the 34dB. So all the PSNR values are around 50-60 dB.

Tamper detection based proposed approach

We tried to tamper the watermarked image as shown in figure 5 . 28 where the circles illustrates the tampered zones. We extract the watermark from the tampered watermarked image, then we compare the extracted watermark with the original one in order to obtain the tampered blocks.

We note also the differences between the original and extracted watermark for each medical image. In the tamper detection appeared in figure 5.29, we can note that our proposed approach can determine perfectly the tampered blocks.

Comparative study

In order to prove the robustness and capacity of our method, we compared the payload and image quality with the work in [ Walia 13 Based on our results, we note our approach is perfectly detected the tempered zone. Moreover, our work carries more watermark bits with a higher quality and less degradation than [ Walia 13].

Weber conclusion

In this approach, we presented a novel semi-blind watermarking technique in spatial domain. The proposed algorithms covered two security issues: the tamper detection and the watermarking robustness. The approach is based on the Weber differential excitation descriptor. We have tested our approach on different medical images with several scenarios of attacks and we have obtained a high efficiency of our algorithms both for robustness and tamper detection.

Chapter 5: Watermarking Approaches

5.5A Novel CT Scan Images Watermarking Scheme in DWT Transform Coefficient

In this part, we present our watermarking framework in the frequency domain based on DWT technique, which makes it possible to ensure the image's authenticity and, as a consequence, the reliability. Our approach also presents a high robustness and less complexity regarding the proposed algorithms in the literature.

In our approach, we apply one level DWT for both the used watermark and the original images. Then, we embed the watermark in the original image by using linear interpolation presented by our team in previous works such as [Laouamer 13], [ Benhocine 13], [Benhocine 08] and [Benhocine 09]. Linear interpolation provides an imperceptible watermark without degradation in the quality of the watermarked image. However, the novelty and the contribution of this approach is in the extraction phase, which takes into account the watermarked image in the extraction process and not just the attacked watermarked image.

In the second section we present the wavelets decomposition principle. The third section is dedicated to the new watermarking approach we have proposed. In the fourth section, we present the test results of our algorithm. The chapter ends by a conclusion and perspectives in the fifth section. The multi-resolution domain offers several advantages. The first advantage is that it defend for the used watermarking algorithms to be robust against JPEG 2000 compression. The second advantage is its power to choose the frequency set that is watermarked to control the most noticeable visual degradation in low and high frequencies. The embedding in the low frequency sub-band provides a high robustness, but the embedded watermark become visible which affects the image quality. This means a degradation in the watermarked image [ Laouamer 13]. While the embedding in the high frequency sub-band supports more visibility and low degradation, but less robustness [Swami 13].

This property is due to the impairment of the visual human contrast sensitivity at high frequencies [Laouamer 15].

Proposed watermarking approach

In our work, we apply one level DWT for both the used watermark and the original images. Then, we embed the watermark in the original image by using linear interpolation presented by our team in the works [ Laouamer 13], [ Benhocine 13], [Benhocine 08] and [Benhocine 09]. Linear interpolation provides an imperceptible of the watermark without degradation in the quality of the watermarked image.

Our technique considers two phases: embedding and extraction processes. In the embedding phase, one level DWT is applied to the watermark and also to the original image. Then, we embed the watermark using linear interpolation. The inverse DWT (DWT -1 ) is applied to the DWT coefficients of the watermarked image in order to obtain a "readable" watermarked image. In the extraction phase, one level DWT is applied to the watermarked and watermark images. We achieve the embedding process using linear interpolation to get a new watermarked image. Then, the attacked watermarked image and the new watermarked image are used to extract the attacked watermark using the linear interpolation.

Finally, DWT -1 is applied to the extracted attacked DWT watermark image to obtain a readable attacked watermark image.

Chapter 5: Watermarking Approaches

Watermark embedding

Figure 5.31 illustrates the watermark embedding process which is based on the level-1 wavelet decomposition. The watermark is embedded through a linear interpolation where and i, w and i w are respectively the original image, the watermark and the watermarked image.

w DWT , i DWT and i wDWT are respectively the watermark, the original image and the watermarked image in wavelet decomposition. The main steps of the embedding process are as follows:

1. Divide the original image i and the watermark w into 8 × 8 blocks.

2. Apply the DWT (one level) to each block obtained in step one for the images i and w. The matrices of the DWT coefficients give as results the i DWT and w DWT matrices.

Mark w DWT in i DWT by the following equation:

where i wDWT are the watermarked matrices (visually this matrix is unreadable, so to make it readable we need to apply the step 4) and t is a given value .

4. Apply the DWT inverse operation (DWT -1 ) to all the blocks in order to obtain the readable image iw.

Watermark extraction

The novelty and the contribution of this is in the extraction phase, which takes into account the watermarked image in the extraction process and not just the attacked watermarked image. Figure .32 shows the extraction scheme. We denote by "mark", the embedded watermark by linear interpolation, while "extraction" refers to the watermark inverse embedding:

Where w a , i wa and w iDWT are the extracted watermark, the attacked watermarked image and inverse DWT of watermark image, respectively. We summarized this process as follows:

1. Apply the DWT one level for each block of w and i w to obtain w DWT and i wDWT .

2. Mark w DWT in i wDWT by using equation (5.20) to obtain w iDWT.

3.

Apply the DWT one level to each block of the attacked watermarked image i wa to obtain i waDWT which is the DWT coefficient matrix of the attacked watermarked image.

4. Unmark i waDWT with the same t value used in the embedding process using the equation (5.21) to obtain w aDWT .

5. Apply the DWT inverse to all the blocks of in order to obtain a readable and significant image w a . Chapter 5: Watermarking Approaches name. The watermarking process has a secret key, that varies exclusively between 0 and 1 in order to achieve a visible /invisible watermarking. We tested our proposed watermarking algorithm against several kinds of attacks of the Stirmark Benchmark [ Laouamer 13] and [Benhocine 09]: median filtering, JPEG compression, rotation, noise and PSNR attacks. Through the obtained results we can conclude that the invisible watermarking (where t is close to 1) gives better results compared to the visible one (t = 0.2) and the semi-invisible one (t = 0.5) where the extracted watermarks are similar to the original one. As for the robustness of the proposed approach, we conducted tests in several cases (according to the values of t). In figure 5.34, the first level (a) shows the attacked watermarked images, the second level (b) shows the extracted attacked watermark image and the third level (c) shows the differences between the original watermark image and the extracted attacked watermark in case of t=0.98. Chapter 5: Watermarking Approaches

Robustness measurements

To assess the robustness of the proposed approach, we introduce the latest techniques used in the literature. It consists to calculate the Peak Signal to Noise Ratio (PSNR), Structural Similarity Index SSIM [ Hore 10] and Universal Quality Index (UQI) [Wang 02] between the original watermark and the extracted watermark as we can see in

Imperceptibility measurements

Our approach achieves a high imperceptibility regarding the watermark embedding. The degradation in the watermarked image after watermark embedding is very low. The optimal imperceptibility in our scheme is when t is close to 1 (t=0.98). We have evaluated the imperceptibility for our approach by measuring the PSNR between the original image and the watermarked image.

Comparative study

In this section, we compare the robustness of the proposed technique with the works in [Ahmad 14] and [Benrhouma 15]. We provided the values of PSNR and SSIM of the extracted watermark. Those works have used the DWT technique, where the watermark image size in those works has the same size with the watermark used in our work. It is obvious from the table 5.25 and 5.26, and figures 5.47 and 5.48, that our results are better than those results in term of robustness by measuring the PSNR.

Attacks

DWT conclusion

We proposed in this part a new watermarking approach to ensure the CT scan medical image authentication and robustness, which is based on the wavelet transform. This approach is applicable to any kind of images, but more appropriate to the medical image because it maintains a high image quality and generates less degradation than existing methods. The embedding process is performed by a linear interpolation which makes it possible to have an inverse watermark after embedding. Our tests were performed on a sample of 250 images. The results obtained are very encouraging, especially when the watermark is invisible (the watermarking key t close to 1). We have evaluated the robustness of our approach by comparing the original watermark and the extracted one after applying attacks. The comparison has been achieved by applying the best known similarity measures between the original and the extracted watermarks as the PSNR, SSIM, UQI. The experimental results and the comparative study show that the proposed technique present more robustness against different kinds of attacks than some relevant works presented in [Ahmad 14] and [Benrhouma 15].

Conclusion

In this chapter, we presented our contributions in watermarking field. They consist of thress solutions in the spatial domain (FCA, ZBDD and Weber) and one solution in the frequency domain (DWT).

Chapter 5: Watermarking Approaches Our FCA based watermarking approach is reversible and novel. Its main feature is that it generates the optimal position for embedding. The watermark is built from some header information of the DICOM image. It is embedded into the NROI of the medical image. Based on experimental results, our approach demonstrates a lower computational complexity, using low capacity for the watermark and has a high robustness. Moreover, the approach can detect the removal and/or addition and/or replacement during attacks, which would be useful for tamper detection issues. Although the proposed approach has been limited in this approach to medical image, it could be used with other kinds of images. Moreover, our FCA approach has the ability to detect the attacks by comparing the extracted concepts from the watermarked image after attacks with the original concepts from the original image.

FCA also provided a distribution embedding area making the imperceptibility high.

In ZBDD approach, we addressed the problem of generating watermarks as small as possible (small payload) to adapt the hidden data to real time applications by maintaining high robustness, high imperceptibility and low complexity within a medical image. It is a novel and optimal approach that is completely innovative through its generation of an intelligent (adaptive) watermark based on ZBDD.

ZBDD is a technique which has already proved its usefulness in many applications such as path reduction in wireless networks, production management, etc. An adaptive watermarking method based on Zero-Suppression in ZBDD can generate a watermark with a minimum size while preserving a strong robustness, thus fulfilling the needs mentioned above for low computational complexity and real time applications. We tested our algorithm under several attack scenarios and measured its robustness in the case of invisible watermarking based on linear interpolation. The results obtained show that our techniques represent a new-generation watermarking method offering low complexity, high robustness and imperceptible watermarks. This work compares favorably with the results from other methods in terms of imperceptibility, robustness and capacity.

In Weber approach, we presented a novel semi-blind watermarking technique in spatial domain. The proposed algorithms covered two security issues: the tamper detection and the watermarking robustness. The approach is based on the Weber differential excitation descriptor. We have tested our Chapter 5: Watermarking Approaches approach on different medical images with several scenarios of attacks and we have obtained a high efficiency of our algorithms both for robustness and tamper detection.

Our DWT approach is a new watermarking method to ensure the CT scan medical image authentication and robustness. This approach is applicable to any kind of images, but more appropriate to the medical image because it maintains a high image quality and generates less degradation than existing methods. The embedding process is performed by a linear interpolation which makes it possible to have an inverse watermark after embedding. Our tests were performed on a sample of 250 images. The results obtained are very encouraging, especially when the watermark is invisible (the watermarking key t close to 1). We have evaluated the robustness of our approach by comparing the original watermark and the extracted one after applying attacks. The comparison has been achieved by applying the best known similarity measures between the original and the extracted watermarks as the PSNR, SSIM, UQI. The experimental results and the comparative study show that the proposed technique present more robustness against different kinds of attacks than some relevant works presented in [Ahmad 14] and [Benrhouma 15].

The watermarking approaches provided the way to ensure the authenticity, integrity as well as the copyright issue but they did not ensure the confidentiality of the digital medical image. Cryptography aims to improve the confidentiality of the digital medical image. In the next chapter, we will present a novel and informed symmetric cryptography approach based on N-gram.

Informed Symmetric Encryption Algorithm for DICOM Chapter 6 Medical Image Based on N-grams 6.1 Introduction

There are two basic criteria for the choice of an image encryption/decryption method. The first one is computation complexity (cc), while the second is purely security. As for as cc is concerned, most of public key encryption systems are very slow and need more calculus. For example, the RSA algorithm is considered several hundred times slower than AES in software implementations and it is completely out of touch with hardware implementation. Similarly, it is very difficult and take more time to find the big number factorization in two prime numbers, so it becomes so inappropriate to use RSA comparatively to a symmetric system because the keys are so larger for the RSA and therefore encryption/decryption are getting longer. It is for this reason that they are not suitable for images [Puech 06]. For the security reason, problems related to the structure of public key encryption systems are posed. We note that the necessary keys size in public key cryptosystems to reach adequate security is greater than the key size in secret key cryptosystems. The notion of the importance of the key size to ensure security is not only legitimate in the case of the secret key.

In fact, these systems are based on the hypothesis that the only possible attacks are those we call exhaustive attacks that involve enumerating all possible keys. For example, in the case of a 128 bits key, the size of the enumerated space is 2 128 . But, in the case of the public key, the key size has legitimacy only when considering the same system. Indeed, the 512 bits RSA system for example, is less secure than 128 bits AES system. The only correct way to evaluate a public key cryptosystem is the complexity of the best known attack. What makes the difference; we are never free from theoretical breakthroughs. Very recently, work has successfully factored a 512 bit number [ Ismail 10]. As a result, to have adequate security for the next years, it is generally advisable to use numbers n of 1024 bits.

In this approach, we propose a new way to generate symmetric keys for image encryption / decryption in particularly the medical images by an informed process based on a technique that has been Chapter 6: Informed Symmetric Encryption Algorithm for DICOM Medical Image Based on Ngrams demonstrated on textual analysis called N-grams. We denote by an informed cryptosystem, a system that generates keys based on the original image characteristics to be encrypted. Our obtained results are very significant. We detail them in this chapter.

The organization of this chapter is the following: in the second section the N-grams principle is presented. The third section is dedicated to the proposed algorithm, while, the fourth section presents the experimental results. The chapter ends with the conclusion.

N-Gram

The N-grams technique present many advantages. We cite it's more important one [Brown 92] [ Cavnar 94]:

• Compared to other techniques, the N-grams automatically capture the roots of the most common pixels.

• They operate independently of the nature and the quality of the image. In addition, with the Ngrams, we do not need prior image segmentation.

• They are tolerant to small changes in the pixels intensities, for example, when an image is scanned; the optical recognition is often imperfect. So, it is possible that the pixel of value 220 is read as pixel value ± ε (ε is known as a small value). A system based on pixels will be in difficulty to recognize that it is the pixel with value 220 because of misreading, while, a system based on N-grams is able to take into account the other N-grams in order to keep the recognition performance despite the deformation rate more or less acceptable.

For any given sequence, the N-grams series of this sequence (for n = 2: bigrams, n = 3: trigrams, n = 4: quadrigrams, etc. ...). are as follows: The N-grams principle was applied to the text. We exploit this theory to encrypt/decrypt images with another point of view differently compared to what exists in the literature. So, for a grayscale image of size N × M, the bigrams and trigrams matrix (n = 2, n = 3) of size N × M -1 and N × M-2 respectively are defined as follows: Chapter 6: Informed Symmetric Encryption Algorithm for DICOM Medical Image Based on Ngrams

Sequence (n)=
Original Image I Bigrams Matrix of I ú ú ú ú ú ú ú ú ú ú ú ú ú ú û ù ê ê ê ê ê ê ê ê ê ê ê ê ê ê ë é NM Nj N N N iM ij i i i M j M j
ú ú ú ú ú ú ú ú ú ú ú ú ú û ù ê ê ê ê ê ê ê ê ê ê ê ê ê ë é - - - - - - - - - - NM NM j N j N N N N N iM iM j i j i i i i i M M j j M M j j M M
ú ú ú ú ú ú ú ú ú ú ú ú ú û ù ê ê ê ê ê ê ê ê ê ê ê ê ê ë é - - - - - - - - - - - - - - - - - - - - NM NM NM j N j N j N N N N N N N iM iM iM j i j i j i i i i i i i M M M j j j M M M j j j M M M j

Proposed algorithm based on N-grams

Our proposed approach is illustrated in the following scheme (figure 6.2). We found that the PSNR value is in the vicinity of 72 dB, which means that there is no significant degradation between each original image and the decrypted. The histograms of the original images and those decrypted in figure 6.4 are presented in figure 6.6 and 6.7 (for bigrams and trigrams respectively) show the same distributions of grayscale and the high resemblance between the original image and the decrypted one by measuring also the difference image which very close to the black image.

Conclusion

A limited number of cryptographic methods have been proposed until these days. These methods are mainly based on the key generation either in a symmetrical or asymmetrical way, where each has drawbacks both in terms of slowness (case of asymmetric systems) or secret key security (case of symmetric systems). The work presented in this chapter consisted to discover new perspectives in the field of cryptanalysis. This perspective is based on exploiting the characteristics of the image to generate symmetric keys for image encryption / decryption process which is purely informed. In this process, we have used the N-gram technique. This technique was used in the linguistic engineering and textual analysis. We have implemented this approach for securing medical images in particular.

The used key is generated from the image itself (informed) using N-grams with n = 2 (bigram) and 3 (trigram). The PSNR between the original image and the decrypted image is around 72 dB, while the histograms of the original images and the decrypted images have the same distributions of grayscale and show a high resemblance between the original and the decrypted one. The obtained results are very significant and encouraging.

In the next chapter, we will present a hybrid watermarking and cryptography approach. The technique aims to take advantage of the benefit of both the cryptography and watermarking techniques.

Introduction

In this chapter, we propose a watermarking and encryption system based on a One Time Pad (OTP) encryption algorithm, which generates the key stream using an innovative approach. Indeed, A new chaotic map approach has been proposed and used for key generation.

The proposed hybrid scheme consists in applying a One Time Pad (OTP) encryption algorithm and a semi-blind watermarking approach to the host medical image. The encrypted watermark is embedded in the encrypted host image, directly in the spatial domain. The results obtained show perfect watermark extraction even after applying some attack scenarios.

The organization of this chapter is as follows: in the second section, we present the principles of One Time Pad (OTP) and chaotic maps. The third section deals with the proposed watermarking and cryptographic system. Section four is dedicated to attacking tests and their outcomes and section five for a comparison with other approaches. The chapter ends with a conclusion in section six.

One time pad principle and chaotic maps

One time pad refers to any encryption method in which each byte in the plaintext is encrypted by a corresponding key in the key stream. The one time pad key stream must be generated randomly and each value of the key will be between 0 and 255 in the case of RGB images. The inconvenience of OTP is that the key used cannot be reused more than once. This means that if the same plaintext is encrypted twice, the key will be generated differently. In the encryption process, the key stream should be of the same or a larger size than the plaintext [Rubin 96], [Leone 15].

Theoretically, the OTP cannot be broken because finding the key used for encryption will be a very difficult task, as its length depends on the length of the plaintext. As the plaintext lengthens, this will have an impact on the key length and it will become more difficult to discover the key [Cao 15]. The number of attempts needed to obtain the encryption key is defined by the following equation:

Proposed approach

Our present approach is based on two processes: encryption/watermarking and decryption/extraction.

In the encryption/watermarking process, we first generate the key using our chaotic approach, and Decryption/extraction consists in building the key using the same chaotic map equation. The attacked encrypted watermarked image is decrypted using the same OTP approach. Finally, we extract the attacked watermark image. This process can be summarized as follows.

The encryption and watermarking process

The encryption and watermarking process includes the key generation using our chaotic map. In this process, the encryption is based on the OTP technique. We then proceed to the embedding phase directly in the spatial domain. Here, we illustrate all the steps needed to carry out the encryption/watermarking phase.

Chaotic map key generation

We generate the key with a size n × m using the chaotic map, which is based on the first key (initial value). Any modification in the first key will automatically change the whole key stream. The principle of OTP encryption is to find a different key for each plaintext. We build the key stream defined by a matrix with the same size as the original image. Our chaotic equations are described by the following equations:

(7.1) (7.2) (7.3)
where is the first key element in the key stream; is a constant . is the r th key in the first column . MaxIntensity is the highest value of the pixel intensity, which is equal to 255; and is the key of the row r and the column c such that .

The classical chaotic map provides keys with high sensitivity to the initial value, but without a domain space limit and a lower possibility that values will be similar. Our new formulation of the chaotic map provides us with a key matrix equal to the image size. For each image pixel there is a mismatchspecific key value. So, the similarity in the key values is still lower or may be zero. In order to keep the image information without losing pixel values, we did not exceed the image pixel range. Indeed, the domain space based on our formula is between zero and 255, which is equal to the image pixel range. So, the encryption based on our formula produces an image as a result. Moreover, our formula uses α as the initial value, while it is also the security key for the watermarking. This reduces the complexity of the overall encryption and watermarking process. By providing a high mismatch key based on our formula and the chaotic map condition concerning the sensitivity to the initial value, we can achieve the condition necessary for the OTP, whereby for each pixel we have to encrypt with a difference (one time) key.

Encryption based on OTP and the embedding process in the spatial domain

This step describes the OTP encryption and embedding process, which generates output consisting of an encrypted and watermarked image ENi w . Figure 7.1 illustrates this step. In this phase, we generate the key using our chaotic map. We encrypt the original and the watermark images based on OTP. Then, we embed the encrypted watermark into the encrypted original image by the following steps:

1-Generate the key matrix using equations 7.1, 7.2 and 7.3.

2-Read the original image i.

The decryption and extraction process

To increase the security of our approach, so as to avoid potential hacking, we do not send the key to the receiver side. So, we regenerate the key using equations 7.1, 7.2 and 7.3, illustrated in the encryption phase, and then decrypt the attacked encrypted watermarked image . Finally, we extract the attacked watermark image . The decryption and extraction processes are conducted as follows:

1. Generate the key matrix using equations 7.1, 7.2 and 7.3.

2. Read the attacked encrypted watermarked image .

3. Decrypt the using the following equation: watermarked image in figure 7.3 (e). Also, it is semi-visible in the watermarked image when the α value is 0.5, see figure 7.3 (f). However, the watermark is visible when α = 0.01, figure 7.3 (g). As we can see in these results, the best case for an invisible watermark is one for which the value of α is close to one.

Performance under watermark attacks

In this section, we present the applied attacks to watermarked image. We applied the geometric and non-geometric attacks of table 7

Encryption attacks

For the encryption attack tests, we considered the xor encryption attack as an example in order to evaluate the robustness of our approach, not only against geometric and non-geometric attacks but also for the encryption attacks. In our case, we applied the xor attack with: Here also, we note that the PSNR, NCC and SSIM values are very encouraging, which allows us to conclude that our approach is robust even against cryptographic attacks.

Comparative study

We evaluated the robustness of our encryption and watermarking approach by comparing it with some other known methods proposed in the literature. The results show that our approach is more robust than the others against different kinds of attacks. Table 7.3 gives the results compared with those obtained with the approaches described in s [Guo 15] and [ Zheng 13 It is obvious that the proposed approach gives a better robustness than the methods presented in [Guo 15] and [ Zheng 13].

Conclusion

In this approach, we proposed an innovative hybrid encryption watermarking scheme to improve the security and ensure the integrity of medical image content. The new formula of the chaotic map provided us with a key matrix equal to the image size, where for each image pixel there is a mismatch-specific key value. The generated key stream used for the OTP cryptosystem is based on a new way of applying the chaotic map approach. Here, the initial value of the key stream in the chaotic map is the same as the key used for watermarking, where the embedding and extraction are based on linear interpolation. Medical image encryption and watermarking were done by generating the key stream. A linear-interpolation based watermarking approach was also proposed to reinforce the robustness. The properties of our chaotic map and OTP approach provided us with a reversible and predictable watermarking system. If a change is made to the first value of the key, the extractor can know that there has been tampering based on the linked values of the keys, and can recover the lost data.

Our contribution focuses on a new form of chaotic map to generate keys with specific properties, as well as achieving better efficiency, high robustness and low complexity in the encryption and watermarking approach.

The obtained results are very encouraging with regard to both security and robustness compared with existing techniques. The known similarity measurement metrics PSNR, NCC, SSIM and BER were used to assess the efficiency of the proposed approach.

The experimental results of the watermark extraction prove the efficiency of encryption based on our chaotic map improvement and OTP approach, as the extracted watermark image quality is higher than that produced by the existing encryption and watermarking approaches with which it was compared.

The real advantage is that it offers an improvement of the security of medical images and a protection of the integrity of medical image content compared with other methods.

Conclusion and Future Works

Conclusion and Future Works

Conclusion and Future Works Conclusion

Telemedicine requires high-security. The medical image has to be protected during the transmission.

Confidentiality, authenticity and integrity are the main requirements in the medical field. The watermarking technique can demonstrate and ensure the integrity and the authenticity of the medical image after the transmission, while the cryptography can verify the confidentiality of the medical image.

Nowadays, there are a lot of approaches for securing the digital medical material during the transmission either based on watermarking or cryptography. The exciting security solutions based on the watermarking technique have a gap in the watermarking requirements. The compromise towards an adequate management between robustness and visibility is still unanswered. Moreover, real time application like telemedicine requires less computational complexity, where the time is a very important factor in the telemedicine scenario requirements. The existing approach did not provide a good security solution to dealing with the all telemedicine watermarking requirements. Based on that, we need a watermarking approach to provide a high robustness, low degradation in the watermarked image and less complexity of the embedding and extraction process.

The other way to secure the digital material is based on cryptography technique. The cryptography technique proves the security issue by assuming the intended sender and intended receiver has some security aspects called keys. The existing symmetric cryptography approaches in the medical image have a gap in the security issue of sharing the key while the gap in the existing asymmetric cryptography approaches in the medical image is that it takes a long execution time. On the other hand, the symmetric techniques allow achieving less computational complexity compared to asymmetric techniques while the latter provides a more secure key. So, we need a cryptographic approach to providing the digital medical image with a securing system with less complexity and high-security sharing key.

Conclusion and Future Works

In this chapter, we briefly concludes the thesis and highlights the major contributions. We aim to ensure and prove the security characteristics of the medical image during the transition, which can not only authenticate medical image, but would also be able to prove its integrity and its originality (owner). The authorized user in the telemedicine system would be able to extract the secret information, also the user would be able to detect any modifications in the received medical image.

Finally, this research focuses on supporting the health care production in order to implement a secure, robust and privacy system for the intact sharing and usage of the medical image.

In this thesis, we have proposed robust and innovative watermarking approaches for authenticity and integrity of the digital medical image. Some of them are in the spatial domain, as the approaches are based on the FCA and ZBDD principles. In FCA approach, we investigated a novel and robust watermarking approach in the spatial domain. Our approach is innovative and based on using Formal Concept Analysis to generate the optimal position for embedding. The watermark is built from some header information of the DICOM image. It is embedded into the region of non-interest (NROI) of the medical image. Our approach demonstrates a lower computational complexity, using low capacity for the watermark and has a high robustness. Moreover, the approach can detect the removal and/or addition and/or replacement during attacks, which would be useful for tamper detection issues. In ZBDD approach, we addressed the problem of generating watermarks as small as possible (small payload) based on ZBDD to adapt the hidden data to the real time applications by maintaining high robustness, high imperceptibility and low complexity within the medical image. The results obtained show that our techniques represent a new-generation watermarking method offering low complexity, high robustness and imperceptible watermarks.

Furthermore, we presented a novel semi-blind watermarking techniques in the spatial domain in order to cover two security issues: the tamper detection and the watermarking robustness. The approach is based on the Weber differential excitation descriptor. The obtained approach has a high efficiency. Our algorithms seems to be very good both for robustness and tamper detection issues.

Conclusion and Future Works

Regarding our contribution for watermarking in the frequency domain, we have also proposed a new watermarking approach in the frequency domain to protect and to ensure the CT scan medical image authentication and robustness, which is based on the wavelet transform. It uses a linear interpolation with a coefficient t, the results obtained are very encouraging, especially when the watermark is invisible (interpolation coefficient t close to 1).

Our watermarking approaches either in spatial and frequency domain are semi-blind in order to achieve two goals. One of them is the robustness. The authentic receiver can extract the watermark from the watermarked image in order to ensure the copyright and the owner of the material. The second goal is the authenticity and integrity. The decoder can compare the extracted watermark with the original watermark in order to ensure the authenticity of the digital medical image which can be subject to malicious or unmalicious attacks.

The confidentiality of the medical image is considered in this work by proposing cryptographic approaches which solve some of the problems identified in this domain (complexity, robustness, imperceptibility). In this perspective, we have proposed an approach exploiting the characteristics of the image to generate the key of encryption / decryption. It is purely informed encryption and decryption approach based on N-gram technique. We have implemented this approach for securing the confidentiality of the medical images. The PSNR between the original image and the decrypted image is around 72 dB, while the histograms of the original images and the decrypted images have the same distributions of grayscale and therefore a show high resemblance between the original and the decrypted.

Finally, we proposed an innovative hybrid encryption and watermarking scheme in order to ensure the reliability (integrity and authenticity) and confidentiality of the digital medical image based on OTP and a new chaotic map approach. The new formula of the chaotic map provided us with a key matrix equal to the image size, where for each image pixel there is a mismatch-specific key value. The generated key stream used for the OTP cryptosystem is based on a new way of applying the chaotic map approach. The properties of our chaotic map and OTP approach provided us with a reversible and Conclusion and Future Works predictable watermarking system. The experimental results of the watermark extraction prove the efficiency of encryption based on our chaotic map and OTP approach. The real advantage, compared with other methods is that it contributes to the improving of the security of medical images and of the integrity protection of medical image content.

In this thesis, the two main parameters representing the features of the medical image watermarking, namely the robustness and the execution time were considered.

Our approaches, by comparing with the existing approaches, have high robustness regarding to the geometric and non-geometric attacks. Also, we achieved less degradation in the watermarked image after the watermark embedding, as well as, less execution time for embedding and extraction process.

Furthermore, we have proposed efficient and innovative way to generate an adaptive watermark is proposed. In addition, a novel cryptography approach has been proposed. Its advantages compared with the existing cryptography approaches are that the complexity is low while the key is secure.

Future works

As far as future works are concerned, we plan to continue our research in the following directions:

• Blind image watermarking

The introduced watermarking approach in our thesis is based on a semi-blind watermarking technique. The original watermark is required during the extraction phase. Our approaches provided a good compromising between robustness, imperceptibility, complexity and capacity in the digital medical image field. However, blind watermarking technique increases the security factor in this domain. There are several blind image watermarking approaches that have been presented in the watermarking field. But, their robustness is not high enough in comparison to the semi-blind techniques.

• New measurement tools based on FCA Formal Concept Analysis is a mathematical method. It is presented in chapter 5 section 2. We proposed a robust and low degradation watermarking system, where the FCA principle worked to find the optimal insertion position in the medical image (5.2). We aim to use the FCA principle to measure the image quality by exploiting the image features. The FCA measurement tool will be designed to Conclusion and Future Works measure the degradation either between the original image and the watermarked image to measure degradation due to the watermarking, or between the original watermark and the extracted watermark to measure the robustness of the watermarking technique.

• Relational concept analysis (RCA)

In 5.2, we have presented the FCA principle to find the optimal embedding area in the medical image.

RCA is the extension of the FCA, which provides a conceptual hierarchy. RCA is more general and allows a deeper analysis than FCA. RCA considers several contexts with the relation between them, it takes into account the object categories and links between objects and it provides a set of interconnected lattices. In other words, the relation between objects and attributes can be extended to a relation between concepts (concept relation). By investigating RCA in the watermarking field, we suppose the obtained results will help improve the robustness of the watermarking.

• Orientation Weber law descriptor for tamper recovering

In 5.4, we proposed a novel watermarking technique for two goals. One of them is the robustness and the other is the tamper detection. The approach is based on the first Weber law descriptor (differential excitation ) in order to detect the tampered zones in the watermarked image. However, the approach is discovering the tampered zones but does not recover the original watermark. By using the second Weber law descriptor (Orientation ), we believe that the original image can be reconstructed from the watermark image. The orientation Weber law will provide a blind recovery watermarking system for the original image.

• Chaotic map cryptography

In chapter 7, we presented a new way to generate the encryption and decryption key based on chaotic map. The initial value is the security key that is used in the watermarking system and the other key is linked to the initial value (initial condition). Our chaotic map has provided us with an efficient and effective generating encryption key way, where the key size was the same as the image size.

Moreover, the key is generated one time at the sender and one time at the receiver. However, the link between the secret key and the control factors must be generated accurately to verify that the chaotic map is developing in a chaotic method. We believe that deep study of this approach is still required to improve the security in the algorithm.

Figure 1 .

 1 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

1 :Figure 1 . 2 :Figure 1 . 3 :Figure 1 . 4 :Figure 1 . 5 :

 112131415 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 1 . 6 :

 16 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 1 . 7 :

 17 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 1 .

 1 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 1 . 9 :

 19 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 1 :

 21 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 2 :

 22 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 3 :

 23 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 4 :

 24 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 5 :

 25 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 6 :

 26 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 7 :

 27 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 8 :

 28 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 2 . 9 :

 29 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 3 . 1 :

 31 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 3 . 2 :

 32 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 3 . 3 :

 33 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 3 . 4 :

 34 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 3 . 6 :

 36 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 4 . 1 :

 41 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 4 . 2 :

 42 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 4 . 3 :

 43 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 1 :

 51 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 2 :

 52 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 3 :

 53 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 4 :

 54 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 5 :

 55 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 6 :

 56 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 7 :

 57 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 8 :

 58 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 9 :

 59 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 10 :

 510 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 11 :

 511 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 . 12 :

 512 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 .

 5 Figure 1.1: Data security system [Mousavi 14] .................................................................................... Figure 1.2: Characteristic watermarking system ................................................................................... Figure 1.3: Example of watermarking imperceptibility ........................................................................ Figure 1.4: The trade-off between the three properties watermarking .................................................. Figure 1.5: Watermarking domains ......................................................................................................Figure 1.6: LSB watermarking approach ..............................................................................................Figure 1.7: Local Binary Pattern of eight neighbours. ..........................................................................Figure 1.8: 2-level-DWT decomposition .............................................................................................Figure 1.9: Image DCT frequency coefficients.....................................................................................Figure 2.1: The general encryption and decryption diagram ................................................................Figure 2.2: Cryptography main area .....................................................................................................Figure 2.3: Encryption and decryption process based on symmetric technique ...................................Figure 2.4: Stream cipher diagram ........................................................................................................Figure 2.5: Block cipher diagram .........................................................................................................Figure 2.6: Encryption and decryption process based on asymmetric technique .................................Figure 2.7: DES structure .....................................................................................................................Figure 2.8: AES-128 bit encryption process .........................................................................................Figure 2.9: General idea of meet in the middle attack ..........................................................................Figure 3.1: WFE approach in the case of the embedding-encryption process. ....................................Figure 3.2: WFE approach in case of the decryption-extraction process............................................. Figure 3.3: EFW Approach in case of the encryption-embedding process. .........................................Figure 3.4: EFW approach in case of the extraction-decryption process............................................. Figure 3.5: JWD general diagram .........................................................................................................Figure 3.6: JWE general diagram .........................................................................................................Figure 4.1: General telemedicine scenario ............................................................................................Figure 4.2: Medical image components ................................................................................................Figure 4.3: NROI & ROI medical image ..............................................................................................Figure 5.1: Line diagram of formal concept analysis for images and their features .............................Figure 5.2: Watermark embedding scheme ..........................................................................................Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each submatrix ....................................................................................................................................................Figure 5.4: 144 × 8 Boolean Matrix for each area picked up ...............................................................Figure 5.5: iw and w watermarked and watermark images ..............................................................Figure 5.6: Watermark embedding with different values of t .............................................................Figure 5.7: Watermark extraction scheme ..........................................................................................Figure 5.8: Attacked watermarked and retrieved watermark images..................................................Figure 5.9: Example of a binary tree graph ........................................................................................Figure 5.10: Example of a BDD representing the given function .......................................................Figure 5.11: The BDD for a given combination set ............................................................................Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharing............................ Figure 5.13: Reducing ZBDD represented by a given function ................................Figure 5.14: ZBDD Map for an item set histogram ............................................................................Figure 5.15: Determination of the image main ROI ...........................................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 5 .

 5 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 6 . 1 :

 61 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 6 . 2 :

 62 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 6 . 4 :

 64 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 6 . 5 :

 65 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.17: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function ..................................................................... Figure 5.18: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.19: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ................................................................. Figure 5.20: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function ............................................................................. Figure 5.21: Attacks on the watermarked brain image i wa and the extracted watermarks w a in the case of the Boolean function .................................................................Figure 5.22: Weber Law description................................................................................................... Figure 5.23: 3×3 block ........................................................................................................................Figure 5.24: Original medical images i s ..............................................................................................Figure 5.25: Informed watermark images w s ......................................................................................Figure 5.26: Various watermarked images with different values of α ................................................Figure 5.27: The applied attacks and the corresponding PSNR values ..............................................Figure 5.28: Tampered watermarked images ......................................................................................Figure 5.29:Differences between watermarked image and tampered watermarked image .................Figure 5.30: 2D Medical image wavelet transform with one level decomposition. ...........................Figure 5.31: Watermark embedding process. .....................................................................................Figure 5.32: Watermark extraction process. .......................................................................................Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.34: Watermark extraction results when t=0.98 .....................................................................Figure 5.35: Watermark extraction results when t=0.5 ......................................................................Figure 5.36: Watermark extraction results when t=0.2. ......................................................................Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.38: Watermark extraction results when t=0.98. ...................................................................Figure 5.39: Watermark extraction results when t=0.5. .....................................................................Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key). ..Figure 5.41: Watermark extraction results when t=0.98. ...................................................................Figure 5.42: Watermark extraction results when t=0.5. .....................................................................Figure 5.43: Watermark extraction results when t=0.2. .....................................................................Figure 5.44: Robustness measures in case of SSIM and UQI .............................................................Figure 5.45: Robustness measure in case of PSNR. ...........................................................................Figure 5.46: Imperceptibility results for different values of t .............................................................Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15] ..........Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15] ...........Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver. .........................................................................................................................................Figure 6.2: Proposed system for medical image securing................................................................... Figure 6.3: Example for computing the pixel length matrix ...............................................................Figure 6.4: Results of the bigrams proposed encryption/decryption process .....................................Figure 6.5: Results of the trigrams proposed encryption/decryption ..................................................

Figure 6 . 6 :Figure 6 . 7 :

 6667 Figure 6.6: Histogram of some of tests images ( Case of bigrams) .................................................... Figure 6.7: Histogram of some of tests images ( Case of trigrams) ....................................................Figure 7.1: Encryption and embedding processes ..............................................................................Figure 7.2: Decryption and extraction process ...................................................................................Figure 7.3: Encryption and watermarking results ...............................................................................Figure 7.4: Test results for decryption and extraction ........................................................................Figure 7.5: xor encryption attack example ..........................................................................................

Figure 7 . 1 :

 71 Figure 6.6: Histogram of some of tests images ( Case of bigrams) .................................................... Figure 6.7: Histogram of some of tests images ( Case of trigrams) ....................................................Figure 7.1: Encryption and embedding processes ..............................................................................Figure 7.2: Decryption and extraction process ...................................................................................Figure 7.3: Encryption and watermarking results ...............................................................................Figure 7.4: Test results for decryption and extraction ........................................................................Figure 7.5: xor encryption attack example ..........................................................................................

Figure 7 . 2 :

 72 Figure 6.6: Histogram of some of tests images ( Case of bigrams) .................................................... Figure 6.7: Histogram of some of tests images ( Case of trigrams) ....................................................Figure 7.1: Encryption and embedding processes ..............................................................................Figure 7.2: Decryption and extraction process ...................................................................................Figure 7.3: Encryption and watermarking results ...............................................................................Figure 7.4: Test results for decryption and extraction ........................................................................Figure 7.5: xor encryption attack example ..........................................................................................

Figure 7 . 3 :

 73 Figure 6.6: Histogram of some of tests images ( Case of bigrams) .................................................... Figure 6.7: Histogram of some of tests images ( Case of trigrams) ....................................................Figure 7.1: Encryption and embedding processes ..............................................................................Figure 7.2: Decryption and extraction process ...................................................................................Figure 7.3: Encryption and watermarking results ...............................................................................Figure 7.4: Test results for decryption and extraction ........................................................................Figure 7.5: xor encryption attack example ..........................................................................................

Figure 7 . 4 :

 74 Figure 6.6: Histogram of some of tests images ( Case of bigrams) .................................................... Figure 6.7: Histogram of some of tests images ( Case of trigrams) ....................................................Figure 7.1: Encryption and embedding processes ..............................................................................Figure 7.2: Decryption and extraction process ...................................................................................Figure 7.3: Encryption and watermarking results ...............................................................................Figure 7.4: Test results for decryption and extraction ........................................................................Figure 7.5: xor encryption attack example ..........................................................................................

Figure 7 . 5 :

 75 Figure 6.6: Histogram of some of tests images ( Case of bigrams) .................................................... Figure 6.7: Histogram of some of tests images ( Case of trigrams) ....................................................Figure 7.1: Encryption and embedding processes ..............................................................................Figure 7.2: Decryption and extraction process ...................................................................................Figure 7.3: Encryption and watermarking results ...............................................................................Figure 7.4: Test results for decryption and extraction ........................................................................Figure 7.5: xor encryption attack example ..........................................................................................

1 :

 1 The images and their features .............................................................................................. Table 5.2: The relation between Objects and Attributes ....................................................................... Table 5.3: Formal concepts of data given by the images and their features ......................................... Table 5.4: PSNR quality measurements for extracted watermark after attacks .................................. Table 5.5: NCC results after common image processing attacks ........................................................ Table 5.6: The bits used for the watermark image .............................................................................. Table 5.7: Comparisons of the execution time between the proposed method and the method in [Su 13] ....................................................................................................................................................... Table 5.8: Truth Table for the given Boolean function F ................................................................... Table 5.9: Items set histogram ............................................................................................................ Table 5.10: Item set histogram and binary representation .................................................................. Table 5.11: The available spaces for the item set histogram .............................................................. Table 5.12: Description of the attack types used ................................................................................ Table 5.13: PSNR values between i and iw ........................................................................................ Table

  18: Comparative study of image quality ................................................................................ Table 5.19: PSNR robustness measurements and comparison with the work [Tsougenis 14]. .......... Table 5.20: CC Robustness measurements and comparison with the work [Shahid 12]. .................. Table 5.21: Adaptive watermark image size (bits) and compared with the works [tsougenis 14] and [shahid 12]. ......................................................................................................................................... Table 5.22: Comparison of the payload and imperceptibility with work in [Walia 13] .................... Table 5.23: Robustness measurements after different attacks ............................................................ Table 5.24: Imperceptibility measurement based on PSNR. .............................................................. Table 5.25: PSNR comparative results ............................................................................................... Table 5.26: SSIM comparative results ................................................................................................ Table 7.1: The applied attacks descriptions ........................................................................................ Table

  ] ...........................................................................................................................................

Figure 1 . 1 :

 11 Figure 1.1: Data security system [Mousavi 14] A characteristic watermarking system is shown in figure 1.2 which comprises watermark embedding

Figure 1 . 2 :

 12 Figure 1.2: Characteristic watermarking system

Figure 1 . 3 :

 13 Figure 1.3: Example of watermarking imperceptibility

Figure 1 . 4 :

 14 Figure 1.4: The trade-off between the three properties watermarking

Figure 1 . 5 : Watermarking domains 1 . 4 . 1

 15141 Figure 1.5: Watermarking domains1.4.1 Spatial domainThe spatial domain refers to the fact that the watermark information is embedded directly into the

  into decimal pixel values. In fact, the change is to add or to subtract 1 to the bit value. This change will not affect to the image quality and will not be perceptual. This technique is extremely sensitive to changes and insecure in case of attacks such as noise, rotation, compression or even the act of removing all the least bit [Agung 12] [Chopra 12] [Bajaj 14].

Figure 1 . 5 Figure 1 . 7 :

 1517 Figure 1.7: Local Binary Pattern of eight neighbours.

Figure 1 .

 1 8 presents the general diagram of the second level wavelet decomposition.

Figure 1 . 8 : 2 -

 182 Figure 1.8: 2-level-DWT decomposition

Figure 1 . 9 :

 19 Figure 1.9: Image DCT frequency coefficients.

  There are different software in order to apply different kinds of attacks, especially geometric and non geometric attacks such as Checkmark [Voloshinovskiy 01], Optimark [Solachidis 01], Certimark [CER 00],….. The most known and used is Stirmark [Petitcolas 98, Kutter 99].

Figure 2 . 1 :

 21 Figure 2.1: The general encryption and decryption diagram By C we denoted the cipher text through the channel where C = E (P). At the receiver side, the

  hash function. All of them depend on certain factors called keys [Kotulski 97]. The symmetric encryption uses one key called private key, for both encryption and decryption processes. The asymmetric encryption uses two keys: one of them, called public key is used through the encryption process, the other called the private key, is used through the decryption process. Symmetric encryptions can be divided into two categories: block cipher and stream cipher encryption. The hash Decryption D Encryption E Encryption E Plain Image P Cipher Image C

Figure 2 . 2 : Cryptography main area 2 . 3 . 1

 22231 Figure 2.2: Cryptography main area 2.3.1 Symmetric cryptography Symmetric cryptography is also called single key because it uses one key in both the encryption

  Figure 2.4 illustrates the general encryption and decryption diagram of the stream cipher. In this figure A1, A2,…, An represent the original text and B1, B2,…, Bn represent the ciphered text.

Figure 2 . 4 :

 24 Figure 2.4: Stream cipher diagram The most known techniques in the stream cipher are Rivest Cipher 4 (RC4) [Gupta 14] and one time

Figure 2 . 3 :

 23 Figure 2.3: Encryption and decryption process based on symmetric technique

Figure 2 .

 2 5 illustrates the general encryption and decryption diagram of the block cipher. In this figure, (A1, A2,…, An) represent the original text and (B1, B2,…, Bn) represent the ciphered text.

Figure 2 . 5 :

 25 Figure 2.5: Block cipher diagram The most known techniques in the block cipher are DES [Standard 99] and AES [Chitu 05]. In the

(2. 5 )

 5 for = 1,2,3,. ,n(2.6) where are the cipher and the decrypted text, respectively; E and D are the encryption and decryption operations; is the plaintext; is the key stream that is used for encryption and is the text position. The condition:[Rubin 96].2.4.1.2 Data encryption standard (DES) Data Encryption Standard (DES) is a block cipher symmetric technique. It consists in encrypting 64bit plain text to generate the same size of the ciphered text using 56 bit secret key size[Standard 99].This method has been established by IBM to resolve the need for the data security in their products and it is confirmed by the National Bureau of Standard [Biham 91]. The main idea of the DES is based on the product cipher and Feistel cipher. The product cipher executes several operations to produce a complex encryption function. The internal function of the DES is called a round function which iterates a number of times serially, while the Feistel cipher is the iterated cipher which maps the plain text into the cipher text [Menezes 97]. Figure 2.7 illustrates the working of DES technique.

  where a,b,c,…,n are the 32 bit input; A,B,C,…,N are the 32 bit output; K 1 ,K 2 ,…K n are the secret keys. F is the function in the various rounds, n = 8. The DES is used in wide encryption applications. The first version to reduce DES to eight rounds was in [Biham 91]. After that, many other authors proposed approaches for designing DES secret attack to find all the key possibilities within a short time [Wiener 94], [Rouvroy 03], [Quisquater 05].2.4.1.3 Advanced encryption standard (AES)After the DES algorithm, at the end of the 1990s, the National Institute of Standards and Technology (NIST) declared the need to improve and implement new encryption techniques. A lot of algorithms were suggested. In 2000 the Rijndael algorithm was chosen [Chitu 05]. The algorithm is a block cipher algorithm and it is based on symmetric technique. There were editions AES-128, AES-192 and AES-256 where the block size and the key size of AES-128 is 128, 192 for AES-192 and 256 for AES-256. It is based on the repeated round process. During the round, many operations are performed on the block of data. AES encryption consists of 10 rounds of process for 128 bits, 12

Figure 2

 2 Figure 2.7: DES structure

Figure 2 . 8 :

 28 Figure 2.8: AES-128 bit encryption process

  algorithm comprises the three well known processes: key generation, encryption and decryption.

  ElGammal encryption is an asymmetric technique based on Diffie-Hellman technique. It is defined byTaher in [ElGamal 85]. It has come to solve the difficulties of computing discrete logarithm over limited domain. This method is applied in many cryptography fields. One of them is a digital signature approach. The general diagram of the ElGammal scheme comprises three steps: key generation, encryption and decryption. The key generation phase generates two keys: one of them is public and the other is private which must be kept secret with the sender[Menezes 97].

Figure 2 . 9 :

 29 Figure 2.9: General idea of meet in the middle attack Alice sends the value A= K n and Bob send the value B=K m . Eve computes the value of E=K d by using

  Figure 3.1 illustrates the general diagram of WFE embeddingencryption processes. Figure 3.2 illustrates the WFE decryption-extraction processes [Bouslimi 14].

Figure 3 . 1 :

 31 Figure 3.1: WFE approach in the case of the embedding-encryption process.

Figure 3 . 2 :

 32 Figure 3.2: WFE approach in case of the decryption-extraction process.

2

 2 Encryption followed by watermarking (EFW)In this approach, the encrypted watermark is embedded into the encrypted original data. It comes with the benefit of homomorphism encryption[Bouslimi 14]. This operation is to be conducted in the encryption domain. On the other side, the decoder has to extract the encrypted watermark and encrypted original data then decrypt them. The general diagram of the processes is shown in the figure 3.3 and figure 3.4.

Figure 3 . 3 :

 33 Figure 3.3: EFW Approach in case of the encryption-embedding process.

Figure 3 . 4 :Chapter 3 :

 343 Figure 3.4: EFW approach in case of the extraction-decryption process.

Figure 3 . 5 :

 35 Figure 3.5: JWD general diagramwhere CPDK is the unique specific decryption key and D w is the decrypted watermarked data.

Figure 3 . 6 :

 36 Figure 3.6: JWE general diagram

  Telemedicine back to the 1920s: the radio signals have been used to link public health physician's station of ships at sea with medical emergencies. Telemedicine revolution was in the 1970s: scientific revolution occurred based on the ATS-6 satellite techniques project, wherein, the clinical staff in remote Alaskan and Canadian villages was linked with the main hospitals in distant cities or capitals [Krol 97]. Chapter 4: Digital Medical Image and Telemedicine Security

  digital image is a two-dimensional array of positive integer values where and , and M and N are nonnegative integer values representing the number of row and column, respectively. The coordinate (x, y) represents the image pixel position. represents the image pixel values. In the case of a three dimensional image, is used where , and Y is anonnegative integer[Huang 11 (a)].

  the diagnosis from the expert physician directly after the examinations and images. For each model, different tools and information technology technique are required. [Cavaro 13].

Figure 4 .

 4 Figure 4.1 represents the general idea of using the telemedicine between referring site which involves

Figure 4 . 1 : General telemedicine scenario 4 . 3 . 1

 41431 Figure 4.1: General telemedicine scenario 4.3.1 Telemedicine and teleradiology Teleradiology is a subcategory of telemedicine. It is transmitting the medical image of the patient

  terms demanded to generate a standard format for medical images. Digital Imaging and Communications in Medicine (DICOM) established to be the standard format of medical image in order to store, transmit, save, and use it. DICOM was developed by the corporation between The American College of Radiology (ACR) and National Electrical Manufactures Association (NEMA) to produce standard for data transfer in 1983. In 1985, the ACR-NEMA standard versions 1 published and improved the way to store and transfer the data in a non-proprietary form. The second version enhanced the achievement of the standard definition, data structure and encoding. DICOM version 3 was in 1993, the main difference was based on network protocol by TCP/IP protocol. The data structure model was based on a unique definition for services and objects such as image objects, patient objects, etc.The DICOM's header contains the patient information, physician details and hospital information,where they are known as information object definition IOD. All of these objects in the header have a meaning. The data is divided into several groups, each group contains connected data, such as group 10 which contains the data of patients, the unique identifiers (UID) in terms of technology details in the image such as X-Ray exposure.The DICOM's body contains the important information about the patient case, we can classify the body into the region of interest (ROI) which is normally at the center, and the region of non-interest (RONI) which is the border of the image.

Figure 4 .

 4 2 and 4.3 illustrate the medical image parts [Bairagi 11].

Figure 4 . 2 :Figure 4 . 3 : 4 :

 42434 Figure 4.2: Medical image components

  Schneider 96] [Umamageswari 14] [Lo 14]. In watermarking, embedding invisible information in the host data, then it extracts and verifies the authenticity. The watermarking approach is widely used for the security goal. [Vellaisamy 14] [Memon 14].

  The basic notions in FCA are: a formal context that is a triple set , where I G×M is a binary relation. This triple set can be represented by a cross table, as a set of rows G (formal objects) and a set of columns M (formal attributes); the points where they cross represent the relation I. The notation gIm stands for (g, m) I, which is read as: the object g has the attribute m [Ganter 12]. Î Two sets and are defined:(5.1)the set of all objects in G sharing all attributes in X (5.2)the set of all attributes in M falling under all objects in Y A formal concept is considered to be a unit of two parts: the Extent (a set of objects), and the Intent (a set of attributes) such that all the objects in Extent have all the attributes in Intent and conversely i.e.

  is a super-concept of (A1, B1). The relation sub-concept-super-concept is denoted by ≤. Being a subconcept of a super-concept means that the extension of the sub-concept is contained in the extension of the super-concept, which is equivalent to the relationship where the intention of the super concept contains the intention of the sub-concept[Zenou 04].

Figure 5 . 1 :

 51 Figure 5.1: Line diagram of formal concept analysis for images and their features5.2.2 FCA domainsThe FCA application is very diverse, since FCA has been applied with some disciplines such as

Figure 5 . 2 : Watermark embedding scheme 1 -

 521 Figure 5.2: Watermark embedding scheme

Figure 5 . 3 :Figure 5 . 4 :, 4 -

 53544 Figure 5.3: (a) Extraction of four 12 × 12 sub-matrices from i, (b) Decimal representation of each sub-matrix

Figure 5 . 5 :

 55 Figure 5.5 A illustrates the watermarked image after embedding the four watermark images

Figure 5 . 6 :

 56 Figure 5.6: Watermark embedding with different values of t (a) Original image, (b) and (c) watermarked images

  watermarked image in the FCA concept positions. Figure5.7 illustrates the extraction scheme for our approach.

Figure 5 . 7 :Figure 5 . 8 :

 5758 Figure 5.7: Watermark extraction scheme

Figure 5 .Figure 5 . 9 :

 559 Figure 5.9 shows a binary graph representation of F

Figure 5 . 10 :

 510 Figure 5.10: Example of a BDD representing the given function

Figure 5 . 11 :

 511 Figure 5.11: The BDD for a given combination set

Figure 5 . 12 :[

 512 Figure 5.12: Ordinary binary decision diagram: a) node deletion, b) node sharingFor example, in Figure5.12(a), the node x refers to the same function of either of its potential values

Figure 5 . 13 :

 513 Figure 5.13: Reducing ZBDD represented by a given function ZBDD uses algebraic operations to reduce the size of the combination set: these algebraic operations

Figure 5 .

 5 Figure 5.14: ZBDD Map for an item set histogram

Figure 5 .Figure 5 .

 55 Figure 5.15: Determination of the image main ROI

  Figures 5.16, 5.17, 5.18, 5.19, 5.20 and 5.21 below illustrate the watermarks extracted after applying

  Figures 5.16, 5.17, 5.18, 5.19, 5.20 and 5.21 below illustrate the watermarks extracted after applying

Figure 5 .Figure 5 .Figure 5 .Figure 5 .Figure 5 .Figure 5 .

 555555 Figure 5.16: Attacks on the watermarked hand image i wa and the extracted watermarks w a in the case of the Boolean function

Figure 5 .

 5 Figure 5.22: Weber Law description

Figure 5 .

 5 23 shows how to compute the differential excitation of the pixel M(x i , y j ) with

Figure 5

 5 Figure 5.23: 3×3 block

3 -Figure 5 .Figure 5 .

 355 Figure 5.24: Original medical images i s

Figure 5 .

 5 Figure 5.25 presents the informed watermark image built from each original image, while figure 5.26

Figure 5 .

 5 Figure 5.26: Various watermarked images with different values of α

Figure 5 . 5 Brain 2

 552 Figure 5.27: The applied attacks and the corresponding PSNR values

Figure 5 .Figure 5 .

 55 Figure 5.28: Tampered watermarked images

5. 5 . 1

 51 Wavelet decomposition principle Discrete Wavelet transform (DWT) is a mathematical model for decomposing a signal. It is valuable for handling of a non-fixed signals. The decomposition is based on small waves called wavelets. The one level wavelets decomposition principle for a given image is illustrated in figure 5.30. In fact, this decomposition can have several levels called n-levels, multi-resolution domain. The result of this decomposition gives four sub-bands: Low-Low (LL), Low-High (LH), High-Low (HL) and High-High (HH). The LL sub-band contains the estimated original image while the other sub-bands contain the missing details. The LL sub-band output from any stage can be decomposed further [Swami 13].

Figure 5 .

 5 Figure 5.30: 2D Medical image wavelet transform with one level decomposition.

Figure 5 .

 5 Figure 5.31: Watermark embedding process.

Figure 5 .

 5 Figure 5.32: Watermark extraction process.5.5.3 Experimental resultsWe performed our tests on a gray CT scan medical image database that contains 250 images of size

Figure 5 .

 5 33 illustrates the head original image, watermark image and head watermarked images obtained after applying our algorithm with several values of the secret key t (0.2, 0.5 and 0.98) for a visible, semi-visible and invisible watermarking.

Figure 5 .

 5 Figure 5.33: Embedding watermark by linear interpolation with different values of t (secret key).

Figure 5 .

 5 Figure 5.34: Watermark extraction results when t=0.98

Figure 5 .

 5 Figure 5.35: Watermark extraction results when t=0.5 In figure 5.36, the first level (a) shows the attacked watermarked images, the second level (b) shows

Figure 5 .

 5 Figure 5.36: Watermark extraction results when t=0.2.

Figure 5 .

 5 figure 5.41 illustrate the results for used images sample such as: brain and hand image, while figure

Figure 5 .

 5 Figure 5.37: Embedding watermark by linear interpolation with different values of t (secret key).

Figure 5 .

 5 Figure 5.38: Watermark extraction results when t=0.98.

Figure 5 .

 5 Figure 5.39: Watermark extraction results when t=0.5.

Figure 5 .

 5 Figure 5.40: Embedding watermark by linear interpolation with different values of t (secret key).

Figure 5 .

 5 Figure 5.41: Watermark extraction results when t=0.98.

Figure 5 . 42 :

 542 Figure 5.42:

Figure 5 .

 5 Figure 5.43: Watermark extraction results when t=0.2.

Figure 5 .Figure 5 .

 55 Figure 5.44: Robustness measures in case of SSIM and UQI

Figure 5 .

 5 Figure 5.48: SSIM comparative results with the works in [Ahmad 14] and [Benrhouma 15]

Figure 6 . 1 :

 61 Figure 6.1: The process of the proposed system for images securing exchange between the sender and the receiver.

Figure 6 . 2 :

 62 Figure 6.2: Proposed system for medical image securing. Algorithm: 1. Reading DICOM Image // size 256×256 ( grayscale) 2. Apply compression with JPEG Algorithm 3. Compute N-Grams of compressed image // n=2,…,end of the image rows// for our case we take n=2,3 4. Computing the pixel length matrix and consider it as the first key (key1) 5. Decrypting the encrypted image using the both keys, where key2 in represented by the value n of the N-grams.

Figure 6 . 3 :Chapter 6 : 6 . 4 Figure 6 . 4 :Figure 6 . 5 :Figure 6 . 6 :Figure 6 . 7 :Chapter 6 :

 63664646566676 Figure 6.3: Example for computing the pixel length matrix (a) Original input, (b) Corresponding pixel length matrix.

Chapter 7 : 7

 77 Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map Efficient and Robust Encryption and Watermarking Technique Chapter Based on a New Chaotic Map Approach

Chapter 7 :

 7 Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map where is the key stream for index , and is the length of the plaintext.One Time Pad can be represented by the following equation:for = 1, 2, 3,…., nwhere is the ciphered text; E the enciphering operation; is the plaintext; is the key stream that is used for encryption and is the text position.There are many ways to generate the key, one of which is called Auto Key. Auto Key generates the key in a simple and straightforward manner. The new value of the key has no correlation or fixed relation with the original key stream[Rubin 96]:Let A and B be two independent simple substitutions. Let L be the new key stream for A and B substitutions, so: for = 2, 3,…., n where is the first key, which will be used for the first plaintext; is the first value in the substitution A, and is the last value in the substitution B. Auto key guarantees that the key will be the whole of key stream and that there is no similarity in the key's values[Rubin 96].Chaos theory explains the result of a technique that is highly sensitive to the initial conditions[Kocarev 01]. A Chaotic map is a method that generates the stream of values based on the first generated value by making some small changes in the next stream value. This method is applied in many fields like compression, encryption and modulation. The chaotic map is widely used in cryptosystems[Yap 15]. It is used in cryptography because of its predictable nature and its sensitivity to the initial value[Sneyers 97].

Chapter 7 :

 7 Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map then encrypt the original and the watermark images by applying our OTP approach. Then, we embed the encrypted watermark into the encrypted original image in the spatial domain.

Chapter 7 :

 7 Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map

Figure 7 . 1 :

 71 Figure 7.1: Encryption and embedding processes where . i, w, ENi, ENw and ENi w are the original image, original watermark image, encrypted original image, encrypted watermark image and encrypted watermarked image,

7 :

 7 Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map 3-Read the watermark image w. 4-Encrypt the original and the watermark images using the following equations: m and n are the image size; x=1,…,m. y=1, …,n. ENi and ENw are the encrypted original image and encrypted original watermark, respectively. 5-The obtained encrypted image is embedded by a linear interpolation as defined in the following equation: (7.6)

(7. 7 )Chapter 7 :

 77 Figure 7.2 illustrates the decryption and the watermark extraction process.

Figure 7 . 2 : Decryption and extraction process 7 . 4

 7274 Figure 7.2: Decryption and extraction process

Figure 7 . 3 :

 73 Figure 7.3: Encryption and watermarking results (a) original image, (b) watermark image, (c) encrypted original image, (d) encrypted watermark, (e) encrypted watermarked image with α = 0.99, (g) encrypted watermarked image with α = 0.5, (f) encrypted watermarked image with α = 0.01.

Figure 7 .

 7 4 illustrates different kinds of attacks where the attacks descriptions are illustrated in table 7.1.

Figure 7 . 4 :

 74 Figure 7.4: Test results for decryption and extraction

Figure 10 .

 10 Figure 10.5 illustrates the extracted watermark obtained after the xor attack. To assess the robustness

Chapter 7 :

 7 Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map

Figure 7 . 5 :

 75 Figure 7.5: xor encryption attack example (a) attacked encrypted watermarked image, (b) encrypted watermarked image, and (c) extracted watermark

Chapter 7 :

 7 Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map

  Table Of Contents ......................................................................................................................................... 3

6: LSB watermarking approach

  1 while the N represents the Most Significant Bit (MSB) as we illustrated in the following figure (figure 1.6).

	Bit Position	N(MSB)					2	1(LSB)
	Original value (149) 10	1	0	0	1	0	1 0	1
	Watermarked value (148) 10	1	0	0	1	0	1 0	0
	Figure 1.

.2.2 Discrete cosine transform (DCT)

	The inverse DWT (IDWT) is applied to obtain the watermarked image. In the extraction phase, three calculated the image feature matrix and applied hash function for each sub-bands (LL, LH, HL, HH).
	level DWT is applied to the watermarked image and the original image. Then, by using the linear Then, based on XOR function, they embedded the watermark into the original image. Finally, the
	interpolation 1.3 can retrieve the embedded watermark or by 1.4 to retrieve the original image. inverse DWT is applied. The image features are analyzed into its factored form using DWT. The
	LL2 produced coefficient data are quantized to obtain the image hash. The proposed approach achieved LH2 LH1 (1.3)
	HL2 HH2 high PSNR (good quality) with low computational complexity and execution time.
	(1.4)
	HL1 are the low frequency retrieved watermark, low frequency retrieved original HH1 1.4DCT transforms a signal from the spatial domain to frequency domain [Paunwala 12]. It provides a where and
	image, respectively. high robustness against the JPEG standard for image compression [Tataru 12]. It transforms the image
	The approach provides acceptable imperceptibility if q is close to zero and k is close to one. If the into non-overlapping m × m blocks where the left top coefficient is DC coefficient value and the
	extractor wants to retrieve the watermark image, the original image is required. If he/she wants to others are AC coefficients [Laouamer 12]. Normally, the block size is 8 by 8 items. The human eyes
	retrieve the original image, the original watermark is required. The approach is robust against frequent are more sensitive to low frequencies than high frequencies. DCT splits the image into three different
	attacks, but it has low robustness against noise attacks. frequency bands: low, middle and high frequency. The low frequency contains the major information
	In the work of [Basheera 11], it is proposed a blind watermarking technique. The watermark is
	embedded as a secrete medical information into host color image using DWT. The watermark is
	embedded in the low level (LL) sub bands of the blue channel of the original image. The embedding
	process is: decomposition of the host image into three color channels, embedding of the watermark
	into the LL sub band of the blue color channel of the host image based on discrete wavelet transforms
	], Ahmad et al. proposed non-blind watermarking techniques in the frequency domain in (DWT) three levels. Then, they compressed the data with Zigzag techniques to convert two
	three levels DWT. The watermark is embedded in the low frequency sub-band using blending dimensions to one dimension image. Finally, inverse DWT is applied to obtain the perceptual
	technique. In the embedding phase, three level DWT is applied to the original and the watermark watermarked image. In the extraction process, the watermarked image is decomposed based on DWT,
	image. Then, they embed the watermark in the original image by using the linear interpolation (1.2) the LL sub-band is divided into three color channels. The blue channel is chosen. Then inverse Zigzag
	technique is applied to obtain two dimension blue channel image. Finally, inverse DWT is applied to
	(1.2) achieve the watermark image. The experimental result shows that the method is imperceptible and
	where gives a high quality without attacks. But it also shows that the method has a low robustness against is the third level DWT watermarked image, k and q are factors , is the third
	level DWT watermark, cropping, filtering and noising attacks. is the third level DWT original image.
	[Maneesha 15] proposed a digital image watermarking technique in the frequency domain based on
	DWT. The original image and the watermark image are decomposed into two levels DWT. Then, they

  Hash function is used to generate the hash value of a given text for cryptography requests like text Digital Image Cryptography modification in the input text will provide us with a different text as output, which is farthest from the previous one[William 06].The hash function is a one way function. It generates a fixed message size from variable message size.It is hard to find the plain message from the given hash message[Ferguson 01].The hash function can be classified into two main categories depending on the use or not of a key: hash function which depends on the secret key called keyed hash function and hash function which does not depend on a secret key called un-keyed hash function. An example of this type is Message Authenticate Code (MAC)[Procter 14]. The un-keyed hash functions[Menezes 97] are the Message

	Chapter 2:
	Public Key
	Encryption
	Algorithm
	Original Text	Encrypted Text
	Decryption
	Algorithm
	Private Key

integrity, text authentication, and other security facilities [Mel 01]. Hash function agrees variable input message sizes and generate static size output. It is called the hash code. Any slight change or Digest 4/5(MD4, MD5) [Gupta 14 (a)] and Secure Hash Algorithm 0/1(SHA-0,SHA-1) [Biham 15]. The hash function is recognized as message abstract, hash code, digital fingerprint and checksum [Chakraborty 14].

Hash functions can also be classified in two categories depending on the strength of the one way function. Indeed, there are two types of one way function: weak function and strong function [Chakraborty 14]. Weak one way function is easy to calculate, however, it is hard to get the inverse from the given hash value. The strong function is complicated to calculate, but it's impossible to find the inverse message from the given hash value. Using hash function in the cryptography means one way function applying which is unable to derive the original message from the given hash value

[Schneier 07

].

Table 5 .2: The relation between Objects and Attributes

 5

	Features	Description
	A	Grayscale
	B	Color
	C	Smooth
	D	Nature
	E	Flat
	F	Attacked
	G	Watermarked

Table 5 .4: PSNR quality measurements for extracted watermark after attacks

 5

	PSNR	AFFINE_5 CROP_50	JPEG_90	MEDIAN_7
		48.4227	41.4469	45.6388	45.7755
		41.8699	43.8399	41.9063	43.6029
		39.4454	38.5097	41.4123	41.0731
		45.5536	39.0599	46.3968	47.1297
	[Li 12]	29.65	27.65	29.27	30.31
	[Tsai 12]	16.58	13.38	26.93	27.25
	[Miao 12]	11.56	10.50	17.61	18.64
	PSNR NOISE_80	ROT_45	ROTCROP_2 ROTSCALE_2
		47.3029	52.2202	47.3536	43.7296
		43.3088	40.6519	42.5764	41.5464
		39.9710	36.9476	39.3824	37.8864
		42.0503	38.8461	42.1563	44.9723
	[Li 12]	12.12	11.58	13.56	14.53
	[Tsai 12]	33.14	31.56	33.55	33.72
	[Miao 12]	7.93	18.65	19.21	19.18

Table 5 .5: NCC results after common image processing attacks

 5

table 5 .

 5

	6. Our original image size is 512 × 512.

Table 5 .6: The bits used for the watermark image

 5

	Time	Proposed method	[Su 13]
	Watermark	0.4125	0.5244
	embedding time
	Watermark extraction	0.3392	0.3701
	time
	Total time	0.7517	0.8945

Table 5 .7: Comparisons of the execution time between the proposed method and the method in [Su 13] any

 5 removal or addition has taken place. For instance, after the extraction phase, we obtained four

	watermarks	By subtracting the	(File Modified Date) from	(Patient Date

Table 5 .8: Truth Table for the given Boolean function F

 5

Table 5 .11: The available spaces for the item set histogram

 5

	Item set histogram	Combinations	Offered spaces (pixels)

  The main region of interest in a medical image (ROI) is the visual part with the most important and relevant information of interest to physicians. Generally, medical images in gray scale are displayed with a black, uniform background. Although this background does not have an interest in itself, it makes it possible to see the ROI more clearly and understand the portions of the image required to make a diagnosis.

	reduction and sharing (fi)
	end
	f = selection among suitable fi
	offered_space=0
	for each CS in f
	offered_space= length(CS)*freq(CS)
	end
	/*generate watermark w
	w= worig(offered_space);
	end
	5.3.2.2 Watermark embedding

Table 5 .13: PSNR values between i and iw

 5 .13, we show the quality of the watermarked image by calculating the PSNR values between the original image and the watermarked image.

	PSNR	Hand	Brain1	Brain2	Leg
	B.F. 1 69.3270	66.8331	82.2948 69.9027
	B.F.2	69.1272	60.9207	75.8523 71.8387
	B.F.3	75.0513	70.5129	84.3446 75.1708
	B.F.4	71.7414	70.5129	84.3446 75.1708

Table 5 .16: Similarity metrics between w and w a in the case of image "brain 2"

 5

	Attacks	BF1		BF2		BF3		BF4
		PSNR	CC	PSNR	CC	PSNR	CC	PSNR	CC
	CROP_50	40.1018 0.9997 29.8648 0.9943 33.8518 0.9976 34.1164 0.9978
	JPEG_90	37.8505 0.9989 29.7957 0.9941 33.9366 0.9976 34.0512 0.9976
	MEDIAN_9	40.0017 0.9997 30.0467 0.9945 33.8998 0.9977 34.0351 0.9978
	NOISE_80	37.9189 0.9988 29.9442 0.9942 33.8388 0.9973 32.9113 0.9971
	ROT_45	37.6157 0.9997 29.9805 0.9943 33.7080 0.9973 33.7733 0.9979
	ROTSCALE_-2 37.3323 0.9987 29.9660 0.9943 34.4483 0.9977 34.8564 0.9978
	Attacks	BF1		BF2		BF3		BF4
		PSNR	CC	PSNR	CC	PSNR	CC	PSNR	CC
	CROP_50	36.2317 0.9980	21.9538 0.9996	39.2713 0.9992 39.2713 0.9992
	JPEG_90	36.9611 0.9980	44.5078 0.9999	39.9858 0.9993 39.9858 0.9993
	MEDIAN_9	36.9611 0.9980	44.5078 0.9999	39.3802 0.9992 39.3802 0.9992
	NOISE_80	35.6333 0.9972	40.4267 0.9991	37.1534 0.9988 35.4368 0.9990
	ROT_45	36.2402 0.9979	47.2953 0.9999	36.4254 0.9989 36.4254 0.9989
	ROTSCALE_-2 36.2317 0.9980	42.6714 0.9997	38.2038 0.9991 38.2038 0.9991
	Attacks	BF1		BF2		BF3		BF4
		PSNR	CC	PSNR	CC	PSNR	CC	PSNR	CC
	CROP_50	36.0896 0.9987	38.3022 0.9993	37.4646 0.9990 37.4646 0.9990
	JPEG_90	36.1037 0.9987	37.3736 0.9990	37.4191 0.9990 37.4191 0.9990
	MEDIAN_9	35.9711 0.9986	38.8671 0.9993	38.5087 0.9992 38.5087 0.9992
	NOISE_80	34.3726 0.9981	36.1465 0.9989	35.3957 0.9984 36.7105 0.9988
	ROT_45	35.6692 0.9987	36.6145 0.9992	37.2541 0.9990 37.2541 0.9990
	ROTSCALE_-2 35.6677 0.9985	39.3871 0.9994	38.6096 0.9992 38.6096 0.9992

Table 5 .19: PSNR robustness measurements and comparison with the work [Tsougenis 14].Table 5 .20: CC Robustness measurements and comparison with the work [Shahid 12].

 55

Table 5 .21: Adaptive watermark image size (bits) and compared with the works [tsougenis 14] and [shahid 12].

 5

	5.21, our approach provided a low

Table 5 .22: Comparison of the payload and imperceptibility with work in [Walia 13]

 5 ], whose authors proposed a watermarking method based on Weber law (table 5.22).

	Chapter 5: Watermarking Approaches
		Images	Payload	PSNR
		Brain		71.39
	Our	Brain 2	7225	68.35
	approach	Hand		69.28
		Leg		70.79
		Head	398	58.67
	[Walia	Brain	431	58.39
	13]	Angio	379	59.65
		Abdome	567	56.90
		n

table 5 .

 5 23, figure 5.44 and figure 5.45.

	Attacks	PSNR	SSIM	UQI
	JPEG	69.1732	0.9997	0.9863
	MEDIAN	51.1326	0.9986	0.9611
	NOISE	41.1456	0.9794	0.9153
	PSNR	65.8942	0.9999	0.9999
	ROTATION 43.2264	0.9713	0.9237

Table 5 .23: Robustness measurements after different attacks

 5

Table 5 .

 5 24 shows the imperceptibility results of different values of t. While figure5.46 shows the chart of these results.

	Image		PSNR
		t=0.2	t=0.5	t=0.98
	Head	39.2345 41.4658 56.3476
	Brain	39.4574 40.6244 54.3487
	Hand	38.5657 41.7065 55.5504

Table 5 .24: Imperceptibility measurement based on PSNR. Figure 5.46: Imperceptibility results for different values of t

 5 Based on the previous table and figure, our approach achieves a high imperceptibility when t=0.98.Moreover, the results indicate that the technique offers a high fidelity and imperceptibility, which means that our approach reserves the image quality after embedding, and there is no degradation effected to the watermarked image.

Table 5 .25: PSNR comparative results Figure 5.47: PSNR Comparative results with the works in [Ahmad 14] and [Benrhouma 15]

 5

		[Ahmad 14] [Benrhouma 15] Proposed technique
	JPEG Compression	28.287	38.71	69.1732
	Noise	20.272	25.74	41.1456
	Median	27.497	14.22	51.1326
	Rotation	43.596	36.68	43.2264

Table 5 .26: SSIM comparative results

 5

  p 1 p 2 p 3 p 4 ,….., p i,… p n Bigrams(n-1)= p 1 p 2 , p 2 p 3 , p 3 p 4 ,….., p i-1 p i,… , p n-1 p n Trigrams(n-2)= p 1 p 2 p 3, p 2 p 3 p 4 , p 3 p 4 p 5 ,….., p i-2 p i-1 p i,… , p n-2 p n-1 p n Chapter 6: Informed Symmetric Encryption Algorithm for DICOM Medical Image Based on Ngrams

  ......... .......... .......... .......... .......... .......... ..........

	p 11		p 12	p 12	p 13	...	p 1	j	1	p 1	j	... ..........	p 1	1	P 1
	p	21	p	22	p	22	p	23	...	p	2	1	p	2	.......	p	2	1	p	2
	p	31	p	32	p	32	p	33	...	p	3	1	p	3	.........	p	3	1	p	3
	... .......... .......... .......... .......... .......... .......... ..........
	p	1	p	2	p			2	p	3	...	p	,	1	p	,	... ..........	p	1	p
																					...
	p	1	p	2	p		2		p	3			...	p	,	1	p	,	...	p	1	p

.

Trigrams Matrix of I

  .1 to the watermarked image. Efficient and Robust Encryption and Watermakring Technique Based on New Chaotic Map

	Attacked encrypted watermarked image Chapter 7: Attack type Cropping	Original image Attack Description Cropping watermarked image (up to 50%) Decrypted attacked watermarked image	Extracted attacked watermark image
	No attacks	JPEG Noise	JPEG compression of watermarked image with a quality factor QF=80 Add 1% salt and pepper noise into the watermarked images.
		Rotation	Rotating image with 45 degree
		Scale	Reduce the watermarked image (up to
	Cropping		30%)
	JPEG
	Noise (salt & pepper)
	Rotation
	Scale

Table 7 .1: The applied attacks descriptions

 7 Also, we calculated the Peak Signal to Noise Ratio (PSNR) values, the Normalized Cross Correlation (NCC), the Structural Similarity Index (SSIM) and Bit Error Rate (BER) between the original watermark w and the extracted watermark w a after applying the different geometric and the nongeometric attacks. The obtained results are given in table 7.2. We note that all the PSNR exceed 34 dB and that NCC and SSIM values are very close to 1. Moreover, BER is close to zero. This means that there is an almost perfect similarity between w and w a .

	Attacks	No Attacks	CROP	JPEG	NOISE	ROT	SCALE
	PSNR	59.1131	51.5059 57.2738 58.7928 51.1538	51.5962
	NCC	0.9974	0.9972	0.9985	0.9975	0.9969	0.9975
	SSIM	0.9992	0.9966	0.9990	0.9991	0.9961	0.9966
	BER	0.0262	0.0641	0.0373	0.0267	0.0620	0.0623

Table 7 .2: Similarity measures between w and w a based on PSNR, NCC and SSIM measures

 7

Table 7 .3: Comparison of the robustness of our method with some other related works [Guo 15] and [Zheng 13]

 7 ].

	Attacks	CROP	JPEG	NOISE	ROT		SCALE
	PSNR/ BER	PSNR	BER	PSNR	BER	PSNR	BER	PSNR	BER	PSNR	BER
	Our Approach 51.50 0.06 57.27 0.03 58.79	0.02	51.15 0.06 51.59 0.06
	[Guo 15]	39	0.05	39.3	0.05	39.8	0.025	38	0.05	38.3	0.05
	[Zheng 13]	37.9	0.07	37.5	0.05	37.8	0.04	37.7	0.1	37.7	0.09

  Kannammal, A., & Subha Rani, S. (2014). Two level security for medical images using watermarking/encryption algorithms. International Journal of Imaging Systems and Technology, 24(1), 111-120. Kavadia, C., & Shrivastava, V. (2012). A Literature Review on Watermarking Techniques. International Journal of Scientific Engineering and Technology, 1, 2277-1581.

	Conclusion and Future Works
	[Kannammal 14]

[Kavadi 12] [Khedr 14] Khedr, H. I., El-Gammal, W., & Zidan, W. I. (2014). Design and Implementation of a Computerized Integrated Nuclear Material Accounting System for Egypt. InInternational Conference on Nuclear Security: Enhancing Global Efforts. Proceedings of the Interational Conference.

ACKNOWLEDGEMENTS

First and foremost I would like to express my special appreciation and thanks to my advisors Professors Laurent Nana, Anca Pascu and Lamri Laouamer, you have been a tremendous mentors for

List Of Publications

Fragile image watermarking approaches

A fragile watermarking is a watermarking which cannot accept the modification or the changing of the image, and for which the watermark is destroyed in case of a modification. It is used for content authentication, integrity and tamper detection applications. We can classify the fragile watermarking into: hard and soft authentication. The hard authentication doesn't allow the changing even if it is occurring from the authorized user and the watermark will be broken. While the soft-authentication accepts slight modification from the authorized user, but the watermark is broken and damaged against intentional and dangerous attacks. Semi-fragile watermarking is also called a soft authentication [Mousavi 14] and [ Malshe 12].

In [Walia 13], proposed a watermarking technique in the spatial domain is presented. The work is based on Weber law and its two properties: differential excitation and orientation. The authors divided the image into 3 × 3 blocks. Then, they computed the differential excitation of the center pixel with its 8 neighbors. The positive excitation value of the neighbor's pixel is selected. Finally, the watermark is inserted and the selected pixel intensity is modified.

The proposed technique has a high imperceptibility; it is sensitive to noise attacks like a Gaussian. It can tolerate compression attacks (JPEG) which are less than 15% compression rate. The localization of the altered region by cut and paste attack was satisfying. It is useful in the hard authentication application.

The authors [Al-Otum 14] have proposed a semi fragile watermarking technique for authentication and tamper detection of gray scale images. The proposed approach is based on a discrete wavelet decomposition algorithm modification. The modification is based on expanded bit multi-scale quantization. The watermark is a random bit sequence and it is expanded into three same watermark values to be embedded in three different spaces. Two level DWT is applied and the low frequency sub band is chosen. The watermark is embedded into LL2, LL HL1 , LL LH1 . The embedding steps are the following: The original image is divided into 4 × 4 blocks using wavelet decomposition. A second decomposition level of wavelet transform is applied in order to build the host matrix. Then, a quantization function is applied for each matrix to obtain the quantization value for each matrix. The Chapter 1: Digital Image Watermarking In the literature review, a lot of watermarking works are applied to the medical image either in the frequency or spatial domains. We have presented some of them. Other works are presented in [ Arsalan 12], [Badshah 15], [ Bhalerao 13] and [Lei 14].

Cryptography and watermarking applications in the medical image

In this type of approaches, cryptography and watermarking techniques are combined to renforce the security requirements [Puech 08]. [Ribeiro 14] proposed software to outsource the medical image in the Cross-Enterprise Document Sharing (XDS). XDS's combination outline offers an essential guideline for sharing the healthcare documents through the medical society. The authors' outcomes are the confidentiality, interoperability and search ability of the medical information in XDS system.

The proposed approach is based on the new searchable encryption system (PPSE). They tried to improve and guarantee the healthcare data protection in the cloud domain.

In [Umamageswari 14], the authors presented encryption and watermarking approach in order to achieve high confidentiality, authenticity and reliability of the medical image. The hash value of the medical image is computed, then the extracted message is encrypted using the RSA technique to get the digital signature. The digital signature and patient information obtained are considered as the watermark. They are embedded in the host image using the reversible watermarking technique. At the receiver side, The receiver extracts the patient information and the digital signature to check its authenticity and integrity also to achieve high confidentiality. The embedding and extraction process based on the secret key to achieve higher authenticate level. The technique provided high capacity (embedding large data) into the medical image. The degradation and the distortion of the medical image data is happening after a compression like JPEG.

The authors in [Kobayashi 09] presented encryption technique of the DICOM images. The original pixel data is encrypted and the encrypted version is stored instead of the original data. The techniques based on three entities: the header data to identify the patient data. The pixel data to validate the image itself. And the authentication entity data to improve the authorship of the image. On the verification side, the authenticating entity has to deal with the stored security data in the header and the pixel data, then the encrypted data has to be decrypted using the security data to determine the The extraction steps can be summarized in the following algorithm (algorithm IV).

Algorithm

Experimental results

We performed our tests on a database of 100 DICOM images and here we took as an example the stomach CT medical database images of size 512 × 512. The original images come from [DICOM] while the watermark contains the four watermark images built from the header of the medical image.

The watermarking process has as the secret key t, which varies exclusively between 0 and 1 in order to achieve visible and invisible watermarking. Similarly, we tested our proposed watermarking algorithm against several kinds of attacks, introduced using Stirmark Benchmark [ Petitcolas 12], such as median filtering, JPEG compression, rotation, etc... We added Gaussian, salt and pepper noise and other attacks as shown in figure 6.8 A, figure 6.8 B shows the retrieved attacked watermarks. Through the obtained results we concluded that the invisible watermarking (t close to 1) gives better results The item set histogram describes the numbers of the combination sets and their frequency in the dataset. As an example, table 5.9 gives the combination sets and their frequencies in the data.

.

Proposed approach to hide data in a medical image

In this section, we present our approach to the watermarking process. Three stages will be discussed.

The first step is the generation of the watermark based on the ZBDD in an informed and adaptive way. The second step is the embedding of the generated watermark in the host image and the last step consists in extracting and examining the watermark after attacks have been applied.

ZBDD-based informed and adaptive watermark generation

As mentioned above, the embedding process requires generation of the watermark. This step is based on ZBDD, which helps us to optimize the size of the generated watermark in an adaptive and informed manner. By informed watermarking, we mean the creation of a watermark based on the existing information of the original media (in our case: the patient name of the header's medical image). By adapting, we mean generation of a watermark with the smallest size possible. This adaptability is an important quality of a practical watermarking method for real-time applications. The process of watermark generation can be summarized as the following steps:

1-Define the Boolean selection function f, whose value is not always zero. In order to illustrate the process, let us consider f defined as follows:

8-Based on the offered spaces, as illustrated in table 5.11, choose the item set histogram that provides enough watermarking space (capacity) and good payload. f7, f5 and even f1 are not appropriated (low capacity). f2 meets the requirements, so we chose f2 with combination {ACH, ACE}. ACH's frequency is 13 and its combination length is three characters (13*3=39 positions). ACE's frequency is 6 and its combination length is also three (6*3=18 positions). Therefore, the total available number of positions for watermark embedding is 57 (39+18=57).

9-Generate a suitable watermark based on the available size of the chosen combination set. The generating algorithm steps are described in the algorithm I.

The watermark-generating algorithm can be summarized in the algorithm I as follows:

Protection des contenus des images médicales par camouflage d'informations secrètes pour l'aide à la télémédecine

Muath AlShaikh

Cette thèse aborde la problématique de l'image médicale en tant qu'élément important de la télémédecine sous l'angle de la sécurité de l'information transmise. Nous appliquons les méthodes de cryptographie, de tatouage de l'image (watermarking) et des méthodes hybrides, cryptographie-watermarking à la sécurité de l'image médicale.

La thèse est structurée en une introduction, une première partie dédiée à l'état de l'art

Introduction

Dans l'introduction, il est présenté l'importance de la sécurité et de la sureté de l'information dans le contexte de l'Internet et des nouvelles technologies.

Summary In French

Par ailleurs, dans le contexte de l'importance croissante dans le monde de la qualité du système médical, la télémédecine occupe un rôle très important. Dans le cadre de cette dernière l'image médicale occupe une place importante.

La protection de l'image médicale comprend au moins deux aspects principaux : la

Summary In French

L'étude comparative réalisée dans la section 7.5 entre cette méthode et celle de [Walia 13] montre que notre méthode donne de meilleurs résultats pour la capacité et la dégradation.

Elle permet une plus grande capacité de la marque avec moins de dégradation que celle de [ Walia 13]. Dans la section 5.5.2 nous présentons le principe de décomposition du signal en ondelettes. Ensuite, dans la section 5.5.

Summary In French

La méthode des N-grams présente plusieurs avantages :

• Elle capte automatiquement les racines de plusieurs pixels communs.

• Les N-grams sont indépendants de la nature et de la qualité de l'image. Par les N-grams nous n'avons pas besoin de faire une segmentation à priori de l'image.

• Ils tolèrent un petit changement de l'intensité des pixels.

L'organisation de ce chapitre est la suivante : dans la section 6.2, nous présentons la théorie des N-grams (bi-grams, tri-grams, ….). La section 6.

Travaux futurs

Les recherches entreprises seront continuées dans les directions suivantes :

• Tatouage aveugle

• Nouvelles mesures de qualité du tatouage basées sur la FCA

• Application de l'analyse des concepts relationnels (Relational Concept Analysis (RCA)) au tatouage de l'image

• Approches de tatouage basées sur le deuxième descripteur de la loi de Weber

Medical Image Content Protection by Secret Information Hiding to Support Telemedicine

Abstract

The protection of digital medical image comprises at least two main aspects: security and authentication. In order to ensure the security, the information has to be protected from the unauthorized users while the authentication confirms that the received data is not affected or modified and is sent by the intended sender (watermarking). The cryptography technique proves the security issues by assuming the intended sender and intended receiver have some security aspects called keys. So, after encryption of the digital material from the sender side, the person who has the key (receiver) can decrypt and access the content of the digital material.

In this thesis, we have brought several contributions. The main one is the provision of robust and reversible medical image watermarking solutions in the spatial domain based respectively on FCA and ZBDD. The second one is a semiblind medical image watermarking approach for the tamper detection. Another contribution is the proposal of a secure symmetric encryption system based on N-gram. The last contribution is a hybrid watermarking and cryptography medical image system which focuses on a new form of chaotic map to generate keys with specific properties, and achieves better efficiency, high robustness and low complexity than the existing approaches.

Keywords: Watermarking, Cryptography, DICOM, Medical Image, Attacks, Robustness, Imperceptibility, ZBDD, FCA, Weber, Chaotic Map, OTP, N-gram.