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Blood culture

A blood culture is a medical laboratory test used to detect bacteria or fungi in a person's blood. Under normal conditions, the blood does not contain microorganisms: their presence can indicate a bloodstream infection such as bacteremia or fungemia, which in severe cases may result in sepsis. By culturing the blood, microbes can be identified and tested for resistance to antimicrobial drugs, which allows clinicians to provide an effective treatment.

To perform the test, blood is drawn into bottles containing a liquid formula that enhances microbial growth, called a culture medium. Usually, two containers are collected during one draw, one of which is designed for aerobic organisms that require oxygen, and one of which is for anaerobic organisms, that do not. These two containers are referred to as a set of blood cultures. Two sets of blood cultures are sometimes collected from two different blood draw sites. If an organism only appears in one of the two sets, it is more likely to represent contamination with skin flora than a true bloodstream infection. False negative results can occur if the sample is collected after the person has received antimicrobial drugs or if the bottles are not filled with the recommended amount of blood. Some organisms do not grow well in blood cultures and require special techniques for detection.

The containers are placed in an incubator for several days to allow the organisms to multiply. If microbial growth is detected, a Gram stain is conducted from the culture bottle to confirm that organisms are present and provide preliminary information about their identity. The blood is then subcultured, meaning it is streaked onto an agar plate to isolate microbial colonies for full identification and antimicrobial susceptibility testing. Because it is essential that bloodstream infections are diagnosed and treated quickly, rapid testing methods have been developed using technologies like polymerase chain reaction and MALDI-TOF MS.

Procedures for culturing the blood were published as early as the mid-19th century, but these techniques were labour-intensive and bore little resemblance to contemporary methods. Detection of microbial growth involved visual examination of the culture bottles until automated blood culture systems, which monitor gases produced by microbial metabolism, were introduced in the 1970s. In developed countries, manual blood culture methods have largely been made obsolete by automated systems.

Medical uses
Blood is normally sterile. The presence of bacteria in the blood is termed bacteremia, and the presence of fungi is called fungemia. Minor damage to the skin or mucous membranes, which can occur in situations like toothbrushing or defecation, can introduce bacteria into the bloodstream, but this bacteremia is normally transient and is rarely detected in cultures because the immune system and reticuloendothelial system quickly sequester and destroy the organisms. Bacteria can enter the blood from infections such as cellulitis, UTIs and pneumonia; and infections within the vascular system, such as bacterial endocarditis or infections associated with intravenous lines, may result in a constant bacteremia. Fungemia occurs most commonly in people with poorly functioning immune systems. If bacteria or fungi are not cleared from the bloodstream, they can spread to other organs and tissues, or evoke an immune response that leads to a systemic inflammatory condition called sepsis, which can be life-threatening.

When sepsis is suspected, it is necessary to draw blood cultures to identify the causative agent and provide targeted antimicrobial therapy. People who are hospitalized and have a fever, a low body temperature, a high white blood cell count or a low count of granulocytes (a category of white blood cells) commonly have cultures drawn to detect a possible bloodstream infection. Blood cultures are used to detect bloodstream infections in febrile neutropenia, a common complication of chemotherapy in which fever occurs alongside a severely low count of neutrophils (white blood cells that defend against bacterial and fungal pathogens). Bacteremia is common in some types of infections, such as meningitis, septic arthritis and epidural abscesses, so blood cultures are indicated in these conditions. In infections less strongly associated with bacteremia, blood culture may still be indicated if the individual is at high risk of acquiring an intravascular infection or if cultures cannot be promptly obtained from the main site of infection (for example, a urine culture in pyelonephritis or a sputum culture in severe community-acquired pneumonia). Blood culture can identify an underlying microbial cause in cases of endocarditis and fever of unknown origin.

The pathogens most frequently identified in blood cultures include Staphylococcus aureus, Escherichia coli and other members of the family Enterobacteriaceae, Enterococcus species, Pseudomonas aeruginosa and Candida albicans. Coagulase-negative staphylococci (CNS) are also commonly encountered, although it is often unclear whether these organisms, which constitute part of the normal skin flora, are true pathogens or merely contaminants. In blood cultures taken from newborn babies and children, CNS can indicate significant infections. The epidemiology of bloodstream infections varies with time and place; for instance, Gram-positive organisms overtook Gram-negative organisms as the predominant cause of bacteremia in the United States during the 1980s and 1990s, and rates of fungemia have greatly increased in association with a growing population of people receiving immunosuppressive treatments such as chemotherapy. Gram-negative sepsis is more common in Central and South America, Eastern Europe, and Asia than in North America and Western Europe; and in Africa, Salmonella enterica is a leading cause of bacteremia.

Collection
Blood cultures are typically drawn through venipuncture. Collecting the sample from an intravenous line is not recommended, as this is associated with higher contamination rates, although cultures may be collected from both venipuncture and an intravenous line to diagnose catheter-associated infections. Prior to the blood draw, the top of each collection bottle is disinfected using an alcohol swab to prevent contamination. The skin around the puncture site is then cleaned and left to dry; some protocols recommend disinfection with an alcohol-based antiseptic followed by either chlorhexidine or an iodine-based preparation, while others consider using only an alcohol-containing antiseptic to be sufficient. If blood must be drawn for other tests at the same time as a blood culture, the culture bottles are drawn first to minimize the risk of contamination. Because antimicrobial therapy can cause false negative results by inhibiting the growth of microbes, it is recommended that blood cultures are drawn before antimicrobial drugs are given, although this may be impractical in people who are critically ill.

A typical blood culture collection involves drawing blood into two bottles, which together form one "culture" or "set". One bottle is designed to enhance the growth of aerobic organisms, and the other is designed to grow anaerobic organisms. In children, infection with anaerobic bacteria is uncommon, so a single aerobic bottle may be collected to minimize the amount of blood required. It is recommended that at least two sets are collected from two separate venipuncture locations. This helps to distinguish infection from contamination, as contaminants are less likely to appear in more than one set than true pathogens. Additionally, the collection of larger volumes of blood increases the likelihood that microorganisms will be detected if present.

Blood culture bottles contain a growth medium, which encourages microorganisms to multiply, and an anticoagulant that prevents blood from clotting. Sodium polyanethol sulfonate (SPS) is the most commonly used anticoagulant because it does not interfere with the growth of most organisms. The exact composition of the growth medium varies, but aerobic bottles use a broth that is enriched with nutrients, such as brain-heart infusion or trypticase soy broth, and anaerobic bottles typically contain a reducing agent such as thioglycollate. The empty space in an anaerobic bottle is filled with a gas mixture that does not contain oxygen.

Many commercially manufactured bottles contain a resin that absorbs antibiotics to reduce their action on the microorganisms in the sample. Bottles intended for paediatric use are designed to accommodate lower blood volumes and have additives that enhance the growth of pathogens more commonly found in children. Other specialized bottles may be used to detect fungi and mycobacteria. In low and middle income countries, pre-formulated culture bottles can be prohibitively expensive, and it may be necessary to prepare the bottles manually. It can be difficult to access the proper supplies and facilities, and in some regions, it may not be possible to perform blood cultures at all.

It is important that the bottles are neither underfilled nor overfilled: underfilling can lead to false negative results as fewer organisms are present in the sample, while overfilling can inhibit microbial growth because the ratio of growth medium to blood is comparatively lower. A 1:10 to 1:5 ratio of blood to culture medium is suggested to optimize microbial growth. For routine blood cultures in adults, the Clinical and Laboratory Standards Institute (CLSI) recommends the collection of two sets of bottles from two different draws, with 20–30 mL of blood drawn in each set. In children, the amount of blood to be drawn is often based on the child's age or weight. If endocarditis is suspected, a total of six bottles may be collected.

Culturing
After the blood is collected, the bottles are incubated at body temperature to encourage the growth of microorganisms. Bottles are usually incubated for up to five days in automated systems, although most common bloodstream pathogens are detected within 48 hours. The incubation time may be extended further if manual blood culture methods are used or if slower-growing organisms, such as certain bacteria that cause endocarditis, are suspected. In manual systems, the bottles are visually examined for indicators of microbial growth, which might include cloudiness, the production of gas, the presence of visible microbial colonies, or a change in colour from the digestion of blood, which is called hemolysis. Some manual blood culture systems indicate growth using a compartment that fills with fluid when gases are produced, or a miniature agar plate which is periodically inoculated by tipping the bottle. To ensure that positive blood cultures are not missed, a sample from the bottle is often inoculated onto an agar plate (subcultured) at the end of the incubation period regardless of whether or not indicators of growth are observed.

In developed countries, manual culture methods have largely been replaced by automated systems that provide continuous computerized monitoring of the culture bottles. These systems, such as the BACTEC, BacT/ALERT and VersaTrek, consist of an incubator in which the culture bottles are continuously mixed. Growth is detected by sensors that measure the levels of gases inside the bottle—most commonly carbon dioxide—which serve as an indicator of microbial metabolism. An alarm or a visual indicator alerts the microbiologist to the presence of a positive blood culture bottle. If the bottle remains negative at the end of the incubation period, it is generally discarded without being subcultured.

A technique called the lysis-centrifugation method can be used for improved isolation of slow-growing or fastidious organisms, such as fungi, mycobacteria, and Legionella. Rather than incubating the blood in a bottle filled with growth medium, this method involves collecting blood into a tube containing an agent that destroys (lyses) red and white blood cells, then spinning the sample in a centrifuge. This process concentrates the solid contents of the sample, including microorganisms if present, into a pellet, which is used to inoculate the subculture media. While lysis-centrifugation offers greater sensitivity than conventional blood culture methods, it is prone to contamination because it requires extensive manipulation of the sample.

Identification
If growth is detected, a microbiologist will perform a Gram stain on a sample of blood from the bottle for a rapid preliminary identification of the organism. The Gram stain classifies bacteria as Gram-positive or Gram-negative and provides information about their shape—whether they are rod-shaped (referred to as bacilli), spherical (referred to as cocci), or spiral-shaped (spirochetes)—as well as their arrangement. Gram-positive cocci in clusters, for example, are typical of Staphylococcus species. Yeast and other fungi may also be identified from the Gram stain. A Gram stain identifying microbial growth from a blood culture is considered a critical result and must immediately be reported to the clinician. The Gram stain provides information about the possible identity of the organism, which assists the clinician in the selection of a more appropriate antimicrobial treatment before the full culture and sensitivity results are complete.

In traditional methods, the blood is then subcultured onto agar plates to isolate the organism for further testing. The Gram stain results inform microbiologists about what types of agar plates should be used and what tests might be appropriate to identify the organism. In some cases, no organisms are seen on the Gram stain despite the culture bottle showing indicators of growth or being reported as positive by automated instruments. This may represent a false positive result, but it is possible that organisms are present but cannot easily be visualized microscopically. Positive bottles with negative Gram stains are subcultured before being returned to the incubator, often using special culture media that promotes the growth of slow-growing organisms.

It typically takes 24 to 48 hours for sufficient growth to occur on the subculture plates for definitive identification to be possible. At this point, the microbiologist will assess the appearance of the bacterial or fungal colonies and carry out tests that provide information about the metabolic and biochemical features of the organism, which permit identification to the genus or species level. For example, the catalase test can distinguish streptococci and staphylococci (two genera of Gram-positive cocci) from each other, and the coagulase test can differentiate Staphylococcus aureus, a common culprit of bloodstream infections, from the less pathogenic coagulase-negative staphylococci. Microorganisms may also be identified using automated systems, such as instruments that perform panels of biochemical tests, or matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), in which microbial proteins are ionized and characterized on the basis of their mass-to-charge ratios; each microbial species exhibits a characteristic pattern of proteins when analyzed through mass spectrometry.

Because bloodstream infections can be life-threatening, timely diagnosis and treatment is critical, and to this end several rapid identification methods have been developed. MALDI-TOF can be used to identify organisms directly from positive blood culture bottles after separation and concentration procedures, or from preliminary growth on the agar plate within a few hours of subculturing. Genetic methods such as polymerase chain reaction (PCR) and microarrays can identify microorganisms by detection of DNA sequences specific to certain species in blood culture samples. Several systems designed for the identification of common blood culture pathogens are commercially available. Some biochemical and immunologic tests can be performed directly on positive blood cultures, such as the tube coagulase test for identification of S. aureus or latex agglutination tests for Streptococcus pneumoniae, and unlike PCR and MALDI-TOF, these methods may be practical for laboratories in low and middle income countries. It is also possible to directly inoculate microbial identification panels with blood from a positive culture bottle, although this is not as reliable as testing subcultured bacteria because additives from the growth media can interfere with the results.

Even faster diagnosis could be achieved through bypassing culture entirely and detecting pathogens directly from blood samples. A few direct testing systems are commercially available as of 2018, but the technology is still in its infancy. Most panels detect only a limited number of pathogens, and the sensitivity can be poor compared to conventional blood culture methods. Culturing remains necessary in order to carry out full antimicrobial sensitivity testing.

Antibiotic susceptibility testing
Antimicrobial treatment of bloodstream infections is initially empiric, meaning it is based on the clinician's suspicion about the causative agent of the disease and local patterns of antimicrobial resistance. Carrying out antibiotic susceptibility testing (AST) on pathogens isolated from a blood culture allows clinicians to provide a more targeted treatment and to discontinue broad-spectrum antibiotics, which can have undesirable side effects. In traditional AST methods, such as the disk diffusion test, pure colonies of the organism are selected from the subculture plate and used to inoculate a secondary medium. These methods require overnight incubation before results can be obtained. There are automated systems which use pre-formulated antibiotic panels, measure microbial growth automatically, and determine the sensitivity results using algorithms; some of these can provide results in as little as five hours, but others require overnight incubation as well.

Rapid administration of effective antimicrobial drugs is crucial in the treatment of sepsis, so several methods have been developed to provide faster antibiotic sensitivity results. Conventional AST methods can be carried out on young growth from the subculture plate, pellets of microorganisms obtained from concentration and purification of the positive blood culture, or directly from the culture bottle. Because direct testing methods do not isolate the organisms, they do not provide accurate results if more than one microorganism is present, although this is an infrequent occurrence in blood cultures. Another source of error is the difficulty in standardizing the amount of bacteria in the sample (the inoculum), which has a profound effect on the test results.

Genetic testing can be used for rapid detection of certain antimicrobial resistance markers. Methods such as PCR and microarrays, which can be performed directly on positive blood culture samples, detect DNA sequences associated with genes that confer resistance, such as the mecA gene found in methicillin-resistant Staphylococcus aureus or the vanA and vanB genes of vancomycin-resistant enterococci. MALDI-TOF has been explored as a rapid antimicrobial sensitivity testing method; principles involve measuring microbial growth in the presence of antibiotics, identifying the breakdown of antibiotics by microbial enzymes, and detecting protein spectra associated with bacterial strains that exhibit antibiotic resistance. Some of these methods can be performed on pellets from positive blood culture bottles. However, the lack of established methodologies for AST by MALDI-TOF limits its use in clinical practice, and direct AST by MALDI-TOF, unlike genetic testing methods, had not been approved by the Food and Drug Administration as of 2018.

Limitations
Blood cultures are subject to both false positive and false negative errors. In automated culture systems, identification of positive bottles is based on the detection of gases produced by cellular metabolism, so samples with high numbers of white blood cells may be reported as positive when no bacteria are present. Inspection of the growth curve produced by the instrument can help to distinguish between true and false positive cultures, but Gram staining and subculturing are still necessary for any sample that is flagged as positive.

Blood cultures can become contaminated with microorganisms from the skin or the environment, which multiply inside the culture bottle, giving the false impression that those organisms are present in the blood. Contamination of blood cultures can lead to unnecessary antibiotic treatment and longer hospital stays. The frequency of contamination can be reduced by following established protocols for blood culture collection, but it cannot be eliminated; for instance, bacteria can survive in deeper layers of the skin even after meticulous disinfection of the blood draw site. The CLSI defines an acceptable contamination rate as no greater than 3% of all blood cultures. The frequency of contamination varies widely between institutions and between different departments in the same hospital; studies have found rates ranging from 0.8 to 12.5 percent.

When faced with a positive blood culture result, clinicians must decide whether the finding represents contamination or genuine infection. Some organisms, such as S. aureus or Streptococcus pneumoniae, are usually considered to be pathogenic when detected in a blood culture, while others are more likely to represent contamination with skin flora; but even common skin organisms such as coagulase-negative staphylococci can cause bloodstream infections under certain conditions. When such organisms are present, interpretation of the culture result involves taking into account the person's clinical condition and whether or not multiple cultures are positive for the same organism.

False negatives may be caused by drawing blood cultures after the person has received antibiotics or collecting an insufficient amount of blood. The volume of blood drawn is considered the most important variable in ensuring that pathogens are detected: the more blood that is collected, the more pathogens are recovered. However, if the amount of blood collected far exceeds the recommended volume, bacterial growth may be inhibited by natural inhibitors present in the blood and an inadequate amount of growth medium in the bottle. Over-filling of blood culture bottles may also contribute to iatrogenic anemia.

Not all pathogens are easily detected by conventional blood culture methods. Particularly fastidious organisms, such as Brucella and Mycobacterium species, may require prolonged incubation times or special culture media. Some organisms are exceedingly difficult to culture or do not grow in culture at all, so serology testing or molecular methods such as PCR are preferred if infection with these organisms is suspected.

History
Early blood culture methods were labour-intensive. One of the first known procedures, published in 1869, recommended that leeches be used to collect blood from the patient. A microbiology textbook from 1911 noted that decontamination of the draw site and equipment could take over an hour, and that due to a lack of effective methods for preserving blood, the cultures would sometimes have to be prepared at the patient's bedside. In addition to subculturing the broth, some protocols specified that the blood be mixed with melted agar and the mixture poured into a petri dish. In 1915, a blood culture collection system consisting of glass vacuum tubes containing glucose broth and an anticoagulant was described. Robert James Valentine Pulvertaft published a seminal work on blood cultures in 1930, specifying—among other insights—an optimal blood-to-broth ratio of 1:5, which is still accepted today. The use of SPS as an anticoagulant and preservative was introduced in the 1930s and 40s and resolved some of the logistical issues with earlier methods. From the 1940s through the 1980s, a great deal of research was carried out on broth formulations and additives, with the goal of creating a growth medium that could accommodate all common bloodstream pathogens.

In 1947, M.R. Castañeda invented a "biphasic" culture bottle for the identification of Brucella species, which contained both broth and an agar slant, allowing the agar to be easily subcultured from the broth; this was a precursor of some contemporary systems for manual blood cultures. E.G. Scott in 1951 published a protocol described as "the advent of the modern blood culture set". Scott's method involved inoculating blood into two rubber-sealed glass bottles; one for aerobes and one for anaerobes. The aerobic bottle contained trypticase soy broth and an agar slant, and the anaerobic bottle contained thioglycollate broth. The lysis-centrifugation method was introduced in 1917 by Mildred Clough, but it was rarely used in clinical practice until commercial systems were developed in the mid-1970s.

Automated blood culture systems first became available in the 1970s. The earliest of these—the BACTEC systems, produced by Johnston Laboratories (now Becton Dickinson)—used culture broths containing nutrients labelled with radioactive isotopes. Microbes that fed on these substrates would produce radioactive carbon dioxide, and growth could be detected by monitoring its concentration. Before this technique was applied to blood cultures, it had been proposed by NASA as a method for detecting life on Mars. Throughout the 1970s and 80s several manufacturers attempted to detect microbial growth by measuring changes in the electrical conductivity of the culture medium, but none of these methods were commercially successful.

A major issue with the early BACTEC systems was that they produced radioactive waste, which required special disposal procedures, so in 1984 a new generation of BACTEC instruments was released that used spectrophotometry to detect CO2. The BacT/ALERT system, which indirectly detects production of CO2 by measuring the decrease in the medium's pH, was approved for use in the US in 1991. Unlike the BACTEC systems available at the time, the BacT/ALERT did not require a needle to be introduced into the bottle for sampling; this reduced the frequency of contamination and made it the first system to provide truly continuous monitoring of blood cultures. This non-invasive measurement method was adopted in 1992 by the BACTEC 9000 series, which used fluorescent indicators to detect pH changes. The Difco ESP, a direct predecessor of the contemporary VersaTREK system which detects gas production by measuring pressure changes, was also first approved in 1992. By 1996, an international study found that 55% of 466 laboratories surveyed were using the BACTEC or BacT/ALERT systems, with other automated systems accounting for 10% of the total.

title: Blood culture


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Almeirim

Almeirim is a city and a municipality in Santarém District, Portugal. The population in 2011 was 23,376, in an area of 222.12 km2. The city proper had a population of 10,520 in 2001.

History
There are vestiges of mid-Paleolithic to Mesolithic period along the territory, including traces from Neolithic, Calcolithic and Bronze Age remnants. The Iron Age also marked this region, with archaeological excavations unearthing settlements and artefacts.

Roman legions of Décimo Junius Brutus occupied the territory, following the Tagus upstream and disembarking in Santarém, where they left their marks. These, along with other groups, occupied arable lands, beginning in the first century A.D. This included the development of agriculture (particularly wheat and olive orchards) and raising of cattle, supporting the establishment of Almeirim along the margins of the Tagus.

References to this municipality, began appearing in the 14th century. With rich lands, the territory supported hunting, extending to Santarém, and proximities of the Tagus and Lisbon. This easy access, made Almeirim a preferred place for the Kings of the second Dynasty, and a winter place frequented by members of Corte, becoming known as the Sintra of Winter. Almeirim, therefore, became an ideal place for relaxation, palace intrigue and romantic encounters in the royal gardens, mixed with resolutions of important negotiations.

King John I, between 1411 and 1423, ordered the construction of a (castellated) royal palace and first residences that contributed to the establishment of the town, with the work to the Al-meirim, that included landscaping, drainage and earthen-works.

In 1483, Almeirim was elevated to the status of municipality, wherein he bestowed a concession on its residents. As a consequence, in 1490, its first almoxarife (sheriff) Álvaro Pires Borges was assigned by King D. John II from the royal guard.

In 1500, the Church of São João Baptista was constructed.

The palace was expanded and improved by Manuel I of Portugal who was in Almeirim several times: in 1510, part of 1513, Christmas of 1514 and all the period between October 1515 and May 1516. John III of Portugal followed his example, and spent similar time in Almeirim. He ordered the construction of a royal palace near the Ribeira de Muge (Muja or Mugem), that became known as Paço da Ribeira de Muge and later, the ''Paço dos Negros', then later the Convent of Nossa Senhora da Serra.

King Sebastian, who frequently visited Almeirim, created a dynastic succession crisis with his disappearance at the Battle of Alcácer-Quibir. Without a successor, the Cortes of Almeirim was opened by Cardinal Henry on 11 January 1580, to decide on the problem of succession. During the Cortes, Febo Moniz, as magistrate of Lisbon, directed his response to the Cardinal, stating "Give this your Highness to a Portuguese prince and all will kiss his hand". But, little was resolved, and the Kingdom eventually began to be governed by Philip II of Spain, beginning the reign of Phillipian Dynastic Union, until 1 December 1640.

At the time Almeirim was visited as a winter resort, where many passed through the roads of the burgh and stayed at the Royal Palace. Gil Vicente, the father of Portuguese theatre, presented many of his farses, comedies and plays, for example "Auto da Fé" in 1510; "Barca da Glória" in 1519; tragic-comedy "Dom Dardos" at the marriage of Infanta D. Isabel with Charles V, in 1525; and in 1526 he presented the farse "O Juiz da Beira", the tragic-comedy "Templo de Apolo", "Breve Sumário da História de Deus" and "Diálogo sobre a Ressurreição". It was also in the palace the Garcia de Resende began printing his Cancioneiro Geral.

In the Memórias Paroquiais (1758) the resident population was just over 302 neighbours.

With the inauguration of the D. Luís bridge in 1881, the connection between Almeirim and Santarém, allowed a significant change in the economy.

In 1935, the Casa do Povo, health centre and dispensary were inaugurated. By the middle of the century (1953), the bullring, a social centre of annual activities was also open to the public.

On 20 June 1991, the settlement was elevated to the status of city.

The municipal assembly approved ARU02, designating the Área de Reabilitação Urbana (Urban Rehabilitation Area) for Almeirim (8902/2014, Diário da República, 147, Série 1) in order to modernize and recuperate many of the historic buildings in the town.

Geography
Almeirim is situated 70 km from Lisbon, and 7 km in Santarém; its neighbours include Alpiarça (to the north), Chamusca (in the east and northeast), Salvaterra da Magos, Coruche (both in the south), Santarém (in the northwest) and Cartaxo (in the south). The municipality is situated on a plain along the Tagus Valley and Lezíria, approximately 3.5 km along the left bank of the Tagus River. The morphology of the terrain is marked by a planar relief with little forests, with cultivation interspersed between pastures and vineyards.

The municipality of Almeirim is subdivided into the following 4 parishes: Two main roadways support the population of Almeirim: the EN114 and EN118, in addition to the inter-community IC10. The construction of the Salgueiro Maia bridge and A13 bridge serves and reinforces the privileged location of Almeirim, in addition to constant traffic from Santarém and the rest of the country.
 * Almeirim
 * Benfica do Ribatejo
 * Fazendas de Almeirim
 * Raposa

Economy
The mainstay of the economy is agriculture, including wine making and modern industry of alimentary products such as fruit juices, processed tomato and canned vegetables (Compal).

Civic

 * Bridge of Raposa (Ponte da Raposa)
 * Building of the Wine/Vineyard Institute of Almeirim (Edifício do Instituto da Vinha e do Vinho de Almeirim)
 * Building of the Almeirim CTT (Edifício dos Correios, Telégrafos e Telefones, CTT, de Almeirim)
 * Bullring of Almeirim (Praça de Touros de Almeirim)
 * Cemetery of Almeirim (Cemetério de Almeirim)
 * Cinema-Theatre of Almeirim (Cine-Teatro de Almeirim)
 * Fountain of São Roque (Fonte de São Roque/Fonte dos Namorados)
 * Hospital of the Misericórida of Almeirim (Hospital da Santa Casa da Misericórdia de Almeirim)
 * Municipal Market of Almeirim (Mercado Municipal de Almeirim)
 * National Republican Guard Post of Almeirim (Posto da Guarda Nacional Republicana, GNR, de Almeirim/Tribunal Judicial de Almeirim)
 * Palace of the Marquesses of Alorna (Palácio dos Marqueses de Alorna/Casa da Quinta de Vale de Nabais)
 * Portico of paço dos Negros (Pórtico de Paço dos Negros/Paço dos Negros da Ribeira de Muge)
 * Residence of Quinta de Santa Maria (Casa da Quinta de Santa Maria)
 * Residence of the Cortes of Almeirim (Casa das Cortes de Almeirim)
 * Residential Home of São José (Lar Residencial de São José)

Religious

 * Church of Santa Marta (Igreja Paroquial de Benfica do Ribatejo/Igreja de Santa Marta)
 * Church of São António (Igreja Paroquial da Raposa/Igreja de Santo António)
 * Church of São João Baptista (Igreja Paroquial de Almeirim/Igreja de São João Baptista)
 * Convent of Serra (Convento da Serra)
 * Monastery of the Third Order of São Francisco of Almeirim (Mosteiro da Ordem Terceira de São Francisco de Almeirim/Escolas Velhas)

Culture
The city is also known for its gastronomy, to which Stone Soup is just one great example. According to the people of Almeirim, a poor friar who was on a pilgrimage stopped in the village of Almeirim and knocked on the door of a house. He was too proud to beg for a bite to eat, so instead, he requested a large pot in which he could make “a delicious and filling.......stone soup”. With arched eyebrows and curious glances, the family invited him into their home and set up a large pot over flickering flames and filled with water. Slowly walking up to the iron clad cauldron, the friar reached into his deep pocket to produce a smooth and well-cleaned stone that he promptly dropped into the boiling water. A little while later he tasted the soup and said that it needed a touch of seasoning. So the wife brought him some salt to add, to which he suggested that maybe a little bit of chouriço (sausage), or pork belly, would be better. Graciously, she obliged and dropped several thick slices into the pot. Then, the friar asked if she might not have a little something to enrich the soup, such as potatoes or beans from a previous meal. With a broad smile, she agreed, and added a healthy portion into the bubbling water. This banter continued back and forth between the family and the friar before he finally announced that he had indeed made a very delicious and filling soup. When the soup was done, the friar fished the stone out of the pot, washed and dried it off, and plopped it back in his pocket for the next time.

Nowadays Almeirim is a gastronomical destiny for Portuguese people, as well as for foreign people, willing to taste this soup.

Notable citizens

 * Ferdinand, Duke of Viseu (1433–1470) third son of Edward, King of Portugal
 * Gonçalo da Silveira (1526–1561) a Portuguese Jesuit missionary in southern Africa.
 * Duarte, Duke of Guimarães (1541–1576) a prince, son of Duarte of Portugal, 4th Duke of Guimarães
 * Cristina Branco (born 1972) a musician and fadista.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Almeirim


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Category:Buffyverse

The Buffyverse is the fictional universe shared by the television series Buffy the Vampire Slayer, Angel and related material, created by Joss Whedon.

title: Category:Buffyverse


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Tinago Falls

Tinago Falls is a waterfall on the Agus River, located in between the town of Linamon and Iligan City, Lanao del Norte in the northern part of the Philippine island of Mindanao. It is one of the main tourist attractions of Iligan, a city known as the City of Majestic Waterfalls.

Tinago is a Filipino term meaning "hidden", the falls being hidden in a deep ravine. Trekking to the falls requires approximately 500 descending steps called the winding staircase.

The falls is high, its very cold waters cascading beautifully into a deep and calm basin-like pool which appears like a blue-colored lagoon. Under the falls is a small cave where people can enter and listen to the rumbling waters.

Legend
Folkways has it that there once lived an influential and powerful Sultan Agok and his wife. They were appointed by their people as their king and queen. But they became too proud of themselves and became selfish rulers of their kingdom. When the sultan's wife was pregnant, an enchantress, disguised as a beggar, begged for their help but instead they exiled and rejected her. Because of this, the enchantress cursed the couple that the child will become ugly but they did not take it seriously and permanently banished the witch.

The child did become pretty. The couple was sad and disappointed, expecting the baby to be as lovely as her mother. They hid the child in a cave to avoid embarrassment and named the baby Tin-ag, which means "hidden face". They visited and took care of the baby in the cave.

When the child grew up, she came out of the cave and became amazed at what she saw. The enchantress, who cursed her parents, saw her and made an offer to transform her into something of great beauty and splendor. She accepted the offer and became the Tinago Falls.

Geography
Tinago Falls is located in a deep ravine in Barangay Ditucalan, Iligan City. The falls plunges 240 ft high from a cliff.

title: Tinago Falls


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Sthiramati

Sthiramati (Sanskrit; Chinese: Anhui 安慧, and Jianhui 堅慧; Tibetan: Blo gros brtan pa) was a 6th-century Indian Buddhist scholar-monk. Sthiramati was a student of a Yogācāra scholar named Gunamati, and he was also a contemporary of another 6th century Yogācāra scholar, Dharmapala of Nālandā. Sthiramati is connected with Valābhi university (present-day Gujarat), and also with Nālandā. Evidence from two inscriptions indicate that a figure named Sthiramati founded a monastery at Valābhi.

Sthiramati is mainly known for his numerous commentaries to Yogācāra and Abhidharma works which synthesized a varied tradition into a more coherent system.

Philosophy
While Sthiramati closely follows the classic philosophy of Yogācāra Buddhism found in the works of Vasubandhu and Asanga, his work also contains several innovative interpretations of Yogācāra philosophy.

One of Sthiramati's innovative contributions is his theory of meaning found in his Triṃśikā-bhāṣya. According to Sthiramati, all language is use is figurative or metaphorical (Sanskrit: upacāra). Drawing on a passage in Vasubandhu, Sthiramati argues that all phenomena (dharmas) are mere mental appearances (nirbhāsa), i.e. mental representations (vijñapti). As such, no word can relate to an objectively existent phenomena (since no such thing exists). Words are only related to constructed mental appearances which come from the dependently arisen transformation of consciousness (vijñāna-pariṇāma). These phenomena deceptively appear as objectively existent things, but are ultimately unreal, like optical illusions. Thus, no words have an objective referent, and thus all language is necessarily figurative, a theory that has been termed pan-figurative or pan-metaphorical.

Sthiramati's philosophy is one of various attempts to systematize and develop Yogācāra Buddhism. His system differed from that of other Yogācāra thinkers of his time, like Dharmapala of Nalanda, in various ways. Their varying interpretations are also discussed in Xuanzang’s (7th century) Chéng Wéishì Lùn. One point of contention was the status of the dependent nature. Sthiramati thought that the dependent nature was characterized by duality (of subject-object), which is the result of false imagination. So for Sthiramati, the dependent nature is empty and not ultimately real. In Sthiramati's system, the only thing that has real existence (dravyasat) is "the bare reality, free from the differentiation into subject and object". This is the true essence of the dependent nature (i.e. the perfected nature). Because of this, Sthiramati's view has also been compared to the Nirākāravāda ("false aspectarian") view of Yogācāra by modern scholars, since he holds that all mental images are unreal and false.

Meanwhile, in Dharmapala's system, the dependent nature is the basis or pivot for both the imagined nature (if the dependent nature is discriminated dualistically) and the perfected nature (if duality is removed). For him, the dependent nature is both empty in one sense (when it is falsely discriminated) but also not-empty is another sense (in its true non-dual structure). Thus, for Dharmapala, the dependent nature and the perfected nature are both real, and they are also understood as being neither the same nor different. Because of this, Dharmapala's view has been seen as prefiguring the Sākāravāda view.

Another disagreement between these two leading Yogācāra interpretations was their understandings of the doctrine of the transformation of consciousness (vijñāna-pariṇāma). According to some Yogācāra thinkers, consciousness transforms into various aspects: the seeing aspect (darśana-bhāga, i.e. subjectivity), the objective aspect (nimitta-bhāga, i.e. all objects of experience), the self-reflexive or self-knowing aspect (saṃvitti-bhāga, a division introduced by Dignaga), and (in Dharmapala's system), awareness of self-awareness (svasaṃvitti-saṃvitti). For Dharmapala, these four divisions were seen as working simultaneously to give rise to experience. However, Sthiramati's system only accepts the first three divisions. Furthermore, for Sthiramati, the first two divisions are imagined and ultimately unreal, while only the self-reflexive aspect is ultimately real. Thus, in Sthiramati's system, there is truly only one aspect (bhāga), one single dynamic self-aware consciousness in which causes and effects arise moment by moment.

The view outlined above is the traditional understanding of Sthiramati's philosophy in Chinese Yogācāra scholasticism. Some modern scholars like Hidenori Sakuma have questioned theis tradition understanding of Sthiramati's Yogācāra views due to a lack of primary source evidence. Sakuma argues that this view derives from the work of Kuiji, and that this is unreliable.

Furthermore, Sakuma also argues that it is likely there were different Indian commentators whose work later became conflated into one figure named "Sthiramati".

Works
Sthiramati wrote ten surviving commentaries on various Buddhist treatises:

Furthermore, "Sāramati" (Chinese: Suoluomodi 娑囉末底) is the author of the Ratnagotravibhāga according to the Chinese translator and scholar Fazang (643–712). However, this is likely to be a different figure than the commentator Sthiramati according to Sakuma. Takasaki Jikido is certain that the author of the embedded commentary (verse and prose) to the core text (verse) of the Ratnagotravibhāga is "Sāramati".
 * 1) The Explication of the Compendium of the Abhidharma (Abhidharmasamuccayavyākhyā; currently in Sanskrit, Tibetan, and Chinese). The Tibetan tradition attribute this text to an author named Jinaputra.
 * 2) The Commentary on the Treasury of Abhidharma [Called] True Reality (Tattvārthā Abhidharmakośaṭīkā, survives in full Tibetan translation and some parts in Sanskrit)
 * 3) The Commentary on the Treatise on the Five Constituents (Pañcaskandhakavibhāṣā; survives in Sanskrit and Tibetan)
 * 4) The Commentary on the Treatise on Mental Presentation in Thirty Verses (Triṃśikāvijñaptibhāṣya; survives in Sanskrit and Tibetan)
 * 5) The Commentary on the Distinguishing of the Middle from the Extremes (Madhyāntavibhāgaṭīkā; survives in Sanskrit and Tibetan)
 * 6) The Commentary on the Comments to the Ornament of [Mahāyāna] Sūtras (*Sūtrālaṃkāravṛttibhāṣya; survives in Tibetan)
 * 7) The Commentary on the Kāśyapa Chapter (*Kāśyapaparivartaṭīkā; survives in Tibetan and Chinese)
 * 8) The Commentary on the Mahāyāna Madhyamaka (Dasheng zhongguan shilun 大乘中觀釋論; survives in Chinese)
 * 9) The Commentary on the Exposition of Akṣayamati (*Akṣayamatinirdeśaṭīkā; survives in Tibetan)
 * 10) A commentary on the Collection of Means of Knowledge (Pramanasamuccaya; currently lost).

title: Sthiramati


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Wikipedia:Articles for deletion/Al Jazeerah

Al Jazeerah was proposed for deletion. This page is an archive of the discussion about the proposed deletion. This page is no longer live. Further comments should be made on the article's talk page rather than here so that this page is preserved as an historic record. The result of the debate was redirect to Al Jazeera

Al Jazeerah
An orphaned disambiguation page. 159.37.7.48 20:36, 6 Dec 2004 (UTC)

 * Keep. Where is the speedy un-VfD?  This has grown tiresome.  [[User:GRider|GRider\talk]] 22:10, 6 Dec 2004 (UTC)
 * Relax, please. The issue is whether or not the Al Jazeerah Information Center needs to be disambiguated?  I'd say that it doesn't.  I'd rather see this redirect straight to the TV channel, but there may be better reasons for the dab than I know.  If this was just a taunt listing, then the user's IP can be held to account.  Geogre 23:03, 6 Dec 2004 (UTC)
 * Keep I think the page is certainly needed, because the TV station is transcribed as Al Jazeera, not Al Jazeerah,a nd the information center is with "h" at the end. So if it would auto relink to TV station, it would be much harder to find the information center article and maybe some of those who would want to find it would believe that there is no such article. DeirYassin 00:23, 7 Dec 2004 (UTC)
 * Keep. It may be orphaned, but I can easily imagine someone looking for either of the articles linked and typing "Al Jazeerah" in the search box, and this disambiguation page clears up the distinction between the two different organizations. I see no reason to delete this. [[User:Livajo|力伟|☺]] 03:19, 7 Dec 2004 (UTC)
 * Keep it. —[[en:RaD Man|RaD Man (talk)]] 04:32, 7 Dec 2004 (UTC)
 * Keep. JamesMLane 03:43, 8 Dec 2004 (UTC)
 * Keep with extreme prejudice. Disambigation pages are supposed to be orphans. sjorford 10:17, 8 Dec 2004 (UTC)
 * As the page's creator, I argue keep on the following grounds: While Al Jazeera TV is by far the more notable of the two in theory, Al-Jazeerah Information Center has a very similar URL and name, and has as a result frequently been quoted by a variety of people who should know better as if it were the TV station. Such quotes generally maintain the spelling difference - that is, spell it with an H - and thus someone looking for information on the source for an "Al-Jazeerah" cite is likely to end up at this disambig page. - Mustafaa 12:36, 8 Dec 2004 (UTC)
 * Keep. Easy mistake to type Al Jazeerah rather than Al Jazeera. BMWman
 * Keep according to the Rand McNally World Guide (selected and adapted from the Columbia Lipincott Gazatteer of the World)'Al Jazira' is the northern section of the riparian plain, corresponding to the ancient Assyria so there are definitely alternate spellings and alternate meanings to the words. Pedant 00:52, 2004 Dec 11 (UTC)
 * Extreme Keep! Disambig pages are supposed to be orphaned!  It says so in the disambig notice.  Disambig pages are meant to aid text searching.  --L33tminion | (talk) 21:00, Dec 11, 2004 (UTC)

This page is now preserved as an archive of the debate and, like other '/delete' pages is no longer 'live'. Subsequent comments on the issue, the deletion or on the decision-making process should be placed on the relevant 'live' pages. Please do not edit this page.


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Lake Overholser

Lake Overholser is a reservoir within the city limits of Oklahoma City, Oklahoma. Lake Overholser is formed by Overholser Dam on the North Canadian River in Oklahoma County, Oklahoma. The lake is 2.9 miles west of Bethany and 4.4 mi from Yukon. Lake Overholser is named after Ed Overholser who was the 16th Mayor of the City of Oklahoma City.

The lake was originally intended to assure an adequate supply of municipal water, since the city depended primarily on the North Canadian River as a source, supplemented by private wells. The need for flood control capability became obvious when the river flooded in 1923. It breached the Lake Overholser Dam, and inundated much of the city.

Lake
The lake covers approximately 1,500 acres (6 km2) and was constructed in 1919 to provide water to a treatment plant. According to USGS, its capacity is 17100 acre-feet The average depth is 6 feet and the maximum depth is only 13 feet.

U.S. Route 66
"The Mother Road" was situated along the North shore of Lake Overholser from 1926 to 1958. A 1958 Route 66 improvement project created a new alignment for the highway that relocated the roadbed about 1/4 mile North of the lake. The original 1926 section of Route 66 still exists and was renamed North Overholser Drive. This includes the picturesque Lake Overholser Bridge. The alignment runs south of the Stonebridge Lake Estates and Ramsey Lake and is considered one of the most scenic sections of the original Route 66.

Dam
The Lake Overholser Dam, designed by Niels Ambursen and built by the Ambursen Construction Company of New York, is 68 feet high and 1258 feetlong. Oklahoma City residents voted a $1.5 million bond issue in 1916 to pay for the project. The dam is built of reinforced poured concrete.

The dam has four distinct sections of buttressed spillways and a solid spillway. A concrete walkway extends across the dam over the buttresses until it comes to the larger spillway, where it is carried by a Pratt through truss.

A concrete wing wall anchors the dam into the eastern river bank. The first span of the dam, between the eastern wing wall and the pump house, is wide. The brick-walled pump house has a gabled tile roof, a small chimney, and two round ventilators. It sits above four arched sluiceway openings.

1923 flood
On October 16, 1923, operators at the central telephone exchange of Oklahoma City began calling to notify subscribers living south of Grand Avenue (now Sheridan Avenue) of an impending flood caused by levee breakage at the recently built City Reservoir (now known as Lake Overholser). The daily newspaper, The Oklahoman, reported that 300 national guardsmen and American Legion volunteers had been sent to organize evacuation of a 117-block area of the city that was expected to be severely impacted by the 25-foot wall of water already heading in that direction.

Later, the paper reported that it was not the dam that had failed, but the embankment (levee) at the west end of the dam that had given way after being battered by flood waters that had built up behind the dam. Within thirty minutes, the initial rush of water had raised the downstream river level by 7 feet. The river held at that leveler two hours, but by then the levee at the east end of the dam failed, sending the downstream river level 2 feet higher in a matter of minutes.

By the time the crisis had passed, Jones, Oklahoma and Spencer, Oklahoma, two towns downstream of Oklahoma City, had been surrounded by water. The official damage estimate was five people confirmed dead and property loss was $3,500,000.

Recreational facilities
Lake Overholser is a popular fishing area for local residents. A covered fishing pier is on the southwest side of the lake. Species of fish include: white bass, bream, bluegill, striped bass, flathead catfish, crappie, carp, catfish and largemouth bass.

Boating is allowed on the lake, but swimming is prohibited. Young students have nicknamed the lake "Lake Holdhercloser" due to the lake being a popular make out spot among teens.

title: Lake Overholser


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Lake Murray

Lake Murray may refer to:

 * Lake Murray (Papua New Guinea), the largest lake in Papua New Guinea
 * Lake Murray (South Carolina), for a time the largest artificial lake in the world
 * Lake Murray (Oklahoma), a lake and the oldest State Park in Oklahoma
 * Lake Murray (California), a reservoir in San Diego

title: Lake Murray


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Keystone Lake

Keystone Lake is a reservoir in northeastern Oklahoma on the Arkansas and Cimarron rivers. It is located upstream about 23 mi from Tulsa. It was created in 1968 when the Keystone Dam was completed. The primary purposes are: flood control, hydroelectric power generation, wildlife management and recreation.

General description
Keystone Lake is about 23600 acre in area, and was designed to contain 505381 acre.ft of water. It was named for the community of Keystone, which existed on the site from 1900 until 1962, when it was inundated by the waters of the lake. Construction of the lake forced the relocation of three other towns: Mannford, Oklahoma (also known as New Mannford by locals), Prue (also known as New Prue), and Appalachia Bay, Oklahoma. The town of Osage was partially abandoned to the lake, while the rest clings to the south shore. Engineers built a levee around low-lying areas of the south and east sides of Cleveland, Oklahoma to prevent flooding of that city. The shoreline extends for 330 mi.

Two Oklahoma state parks, Keystone State Park and Walnut Creek State Park, are located along the shores of the lake offering camping, hiking and biking trails, fishing, swimming and boating opportunities. The area also features a Yogi Bear's Jellystone Park Camp-Resort as you cross the Keystone Dam near Sand Springs.

The Keystone Lake project was authorized by the Flood Control Act of 1950. It was designed and built by the Tulsa District, Army Corps of Engineers. Construction began in January 1957 and was complete for flood control purposes in September 1964. Commercial operation of the power generating facility began in May 1968.

A reregulating dam, located 7.8 miles downstream of the main dam, was also completed in 1968. Cost of the total project was approximately $123 million. In 1986, the reregulating dam was removed due to public safety issues, as 16 people had drowned at the dam.

Dam construction details
The dam was actually constructed across the Arkansas River, downstream of the confluence with the Cimarron River. It is built of rolled earthfill material. Maximum height of the dam is 121 ft above the stream bed. The total length of the dam is 4,600 ft, including a 1,600 ft-long concrete section. The spillway in the concrete section is 856 ft wide. The non-overflow part of the concrete section includes a power intake structure. State Highway 151 crosses the dam, connecting State Highway 51 on the south with U.S. Highway 64 on the north.

The spillway is a gated ogee weir, 720 ft wide with eighteen tainter gates, each 40 by. Spillway capacity at the maximum pool level (elevation 766.0 ft) is 939,000 cuft/s. Capacity at the top of the flood control pool level (elevation 754.0 ft) is 565000 cuft/s. The spillway also has nine sluices, each 5.67 by.

The power intake structure is between the spillway and the left non-overflow section of the dam. It includes two penstocks, each 27 ft diameter and controlled by two 14 by gates. The power generation facility includes two hydroelectric generators, each rated at 35,000 kW.

Largest release in service
In September and October 1986, Keystone Lake was filled to capacity when the remnants of Hurricane Paine entered Oklahoma and dropped nearly 22 inch of water into the Cimarron and Arkansas rivers northwest of the lake, requiring the Corps of Engineers to release water downstream at a rate of 310,000 cuft/s, which made downstream flooding inevitable. As a result, a private levee in West Tulsa failed, causing more than $1.3 million in damages.

Recreation

According to the Corps of Engineers website, Keystone Lake has 16 recreational areas (including 3 alcohol-free beaches), 11 boat ramps, 4 marinas and 2 off-road vehicle areas. There are also campgrounds, a waterfowl refuge and a public hunting area. Keystone State Park nearby offers cabins. Fishing is popular, with the most plentiful species being striped bass, white bass, black bass, small mouth bass, crappie, and catfish. Fauna around the lake include: white-tailed deer, raccoon, bobcat, coyote, beaver, squirrel, cottontail rabbit, quail, dove, ducks and geese. Hunting and fishing licenses are regulated by Oklahoma and Federal laws.

Windycrest Sailing Club offers sailboat racing and cruising.

title: Keystone Lake


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Lake Hefner

Lake Hefner is a reservoir in northwestern Oklahoma City, Oklahoma. It was built in the 1940s to expand the water supply for the city of Oklahoma City,

It is named after Robert A. Hefner, who served as mayor of Oklahoma City from April 11, 1939, to April 8, 1947, but was originally named the "Bluff Creek Reservoir." It also serves as a major recreational destination, as it is surrounded by 9.5 mi of multi-use (bicycle, skating and pedestrian) trails. Stanley Draper was influential in securing the funding to develop the lake.

Description
The capacity of the lake is 75,000 acre-feet. Lake Hefner covers 2,500 acre and averages 29 ft deep. The lake's outflow goes into Bluff Creek which travels north to meet up with Deer Creek, which then flows into the Cimarron River near Guthrie.

The lake is situated within the Oklahoma City urban area and is subsequently closely bordered by residential areas to the north, west, and east. The Lake Hefner Dam is located along the entire northern side of the lake (with Bluff Creek Park being located below the dam, on the other side of Hefner boulevard). Lake Hefner Parkway borders the east side of the lake, with some commercial development (including restaurants, bars and office buildings) located alongside the lake, as well as a 36-foot tall working replica of the second oldest lighthouse in the United States, the Brant Point Light near Nantucket, Massachusetts. The south side of the lake is the least developed, retaining the original forest along much of the shore. Lake Hefner Golf Course is located on the southwest corner of the lake. Immediately south of this are the Oklahoma City docks, commonly known as the city-side docks, the largest marina on the lake. The other marina on Lake Hefner is the Oklahoma City Boat Club (OCBC), a private organization that holds weekly sailboat races during the summer and is located on the east side. Just north of the OCBC is the East Wharf area, which contains several fairly upscale restaurants. On the south side of the lake is the Hobie Point, a YMCA sailing school, and Stars and Stripes Park. Stars and Stripes Park also has new additions of a Fitness court and a Skatepark. The Oklahoma Radio Kontrol Society (TORKS) has maintained a Radio Control air field since the early 1970s.

Recreation

Hefner is also a popular recreational fishing spot for Oklahoma City residents, and is populated with a variety of gamefish species including largemouth & smallmouth bass, channel catfish, walleye, bluegill, black crappie, as well as white bass and hybrid striped bass.

Additionally, Hefner is a popular site for recreational boating, both with sailboats and motorized pleasure craft. Kiteboarding is also very popular on Hefner due to the excellent wind they receive all summer.

title: Lake Hefner


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Great Salt Plains Lake

Great Salt Plains Lake is a reservoir located within the Salt Plains National Wildlife Refuge in Alfalfa County, Oklahoma in the United States named because of the salt flats in the area and for the Salt Fork Arkansas River, which is dammed to form the lake. It is notable for the variety of birds that are attracted to Ralstin Island (not open to the public) and also for the selenite crystals that can be collected along the shoreline. Recent droughts, most notably that of 2011, have had an adverse effect on the future of the lake.

Physical description
A study made in 1931 for the United States Army Corps of Engineers proposed building a flood control dam in the Great Salt Plains area. Congress authorized its construction in 1936. Design studies began in 1937 and the Corps broke ground for construction in September 1938. The dam was completed in July 1941, with a water capacity of 31420 acre-feet. The lake covers 9300 acres and has 91 miles of shoreline. The average depth is 4 feet. The saline content is reportedly one-fourth that of the ocean.

Ralstin Island, created at the same time as the lake, is home to blue heron, great egret and ibis. The island is considered one of the most important colonial bird nesting habitats, and is the largest breeding site in the state for the white-faced ibis. The fish vary from catfish, saugeye (related to the walleye) sandbass and hybrid striped bass.

The State of Oklahoma leased 800 acres on August 1, 1958, for a state park.

Selenite crystals
On the west edge of the lake, visitors can dig for selenite crystals. These crystals feature an hourglass inclusion which is unique to the Great Salt Plains. Scientists believe that salt was deposited during repeated water-level rises of a shallow sea millions of years ago. The supply of salt is kept intact by saline groundwater that flows just a few feet below the surface. When the water evaporates, a layer of salt remains on the surface. This process also plays a role in the formation of selenite crystals that visitors covet.

Future of the lake
The lake is subject to periodic mass fish kills, most recently in 2011. During the extreme drought of that year, the average depth decreased to 2 ft. According to John Stahl, northwest fisheries supervisor for the Oklahoma Department of Wildlife Conservation, the lake has grown more shallow since its creation because of silting and agricultural runoff. That and extremely hot dry summers cause the brine to become more concentrated. Oxygen in the water is mostly consumed by bacteria that break down organic matter in the water, leaving insufficient oxygen to support the fish.

According to officials of the U.S. Army Corps of Engineers, the future of the lake appears grim if no remedial action is taken. Proposed solutions are:
 * Open the dam and allow the lake to flow into the river.
 * Dig the silt out of the reservoir, which could cost $5 – 10 million.
 * Plug the dam to raise the water level.

There is a law requiring that a non federal partner help pay for restoration. The Corps regards this as an unlikely event. If no action is taken, the Corps has said that the seafood source will be depleted and the birds will abandon the lake.

Recreation
Also located along the shores of Great Salt Plains Lake is Great Salt Plains State Park. Recreational opportunities at Great Salt Plains State Park include boating, camping, picnicking, swimming, hiking, mountain biking and exploring. The park has RV and tent sites, comfort stations with showers, cabins, picnic sites, group shelters, swimming beach, playgrounds, boat ramps, fishing dock and equestrian trails.

title: Great Salt Plains Lake


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Lake Eufaula (Oklahoma)

Lake Eufaula, sometimes referred to as Eufaula Lake, is a reservoir in Oklahoma. It is located on the Canadian River, 27 mi upstream from its confluence with the Arkansas River and near the town of Eufaula. The lake covers parts of McIntosh County, Pittsburg, Haskell and Okmulgee counties and drains 47,522 mi2. Water sources include the Canadian, North Fork Canadian and Deep Fork rivers. It is the largest-capacity lake in the state of Oklahoma with a volume of 2099000 acre.ft, a surface area of 102000 acre and 600 mi of shoreline.

History
Congress approved construction of the dam and lake in 1946 to provide flood control, hydroelectric power, water supply, navigation and recreation. The U. S. Army Corps of Engineers began construction of the 975 meter-long (3,199 feet) Eufaula Dam wall in 1956 and was completed in 1964. President Lyndon B. Johnson came to Oklahoma to dedicate the dam on September 25, 1964. The dam holds back a lake area of over 412 km2. The hydroelectric power station was designed to provide 90,000 kilowatts of electric power from the lake waters.

According to the Corps of Engineers in 2015, the Eufaula project cost $121.4 million, and has prevented nearly $575.5 million in flood damages since its completion. The lake attracts about 2.5 million visitors every year.

Heavy rains in the spring of 2015 caused Lake Eufaula to rise so rapidly that the Corps of Engineers opened the flood gates and released water at rates as high as 48000 ft3 per second. This was the highest rate since 1990.

Dam construction
Eufaula Dam is east of the city of Eufaula, Oklahoma. It is 3200 feet long and 114 feet high. It is constructed with an earthen embankment and concrete. The associated hydroelectric power plant has three turbines, each rated at 30 megawatts, for a total installed capacity of 90 megawatts The dam was approved by the Rivers and Harbors Act of 1946 and construction began in 1956. In February 1964, the river was closed and the generators went operational in September 1964. State Highway 71 runs across the top of the dam.

Standing Rock
Standing Rock is now covered by the waters of Lake Eufaula. The historic landmark stood in the middle of the Canadian river about 2 mi below the junction of the North and South Canadians. When the lake is at its top level, 585 ft, the top of the huge upright rock is approximately 25 ft below the surface.

Recreational facilities
Activities at Lake Eufaula include boating, fishing, swimming, hiking, hunting, golfing and horseback riding. Picnic areas are scattered throughout the area. Facilities include marinas, boat ramps, swim beaches, tent and RV campsites, cabins, group shelters, restrooms, showers and an enclosed fishing dock. These can be found at Lake Eufaula State Park and the physically-separate Arrowhead Area at Lake Eufaula State Park.

A well-known tournament lake, Lake Eufaula draws anglers from across the United States to test their skills at catching largemouth bass, smallmouth bass, Kentucky bass, crappie, catfish, sandbass, stripers (below the dam), and other species.

Former State Park Lodges
Oklahoma created two state parks, Arrowhead and Fountainhead, to provide recreational activities and camping facilities at the lake. The tag line in their early advertising was, "Follow the fun to Eufaula." The state borrowed $8 million from the Federal government to build a lodge at each park. However, the lodges did not provide enough money to repay the loan, so ownership reverted to the Federal government. In 1986, the U.S. Economic Administration sold Arrowhead Lodge to the Choctaw Nation and Fountainhead Lodge to a group of private investors. Arrowhead switched hands again in 2000, when a non-profit group with ties to the Church of Scientology bought the lodge and converted it into a drug and alcohol treatment facility, now called Narconon Arrowhead. Fountainhead was sold out of a sheriff's sale to The Muscogee (Creek) Nation in 2005, amid plans to reopen it as a gaming facility. Those plans never materialized, and the lodge was torn down. However, a 48-acre tract of the land was placed into federal trust status in 2018, opening the way for development of the property as a tourist destination with gaming, restaurants and entertainment.

Marinas
List of Marinas on Lake Eufaula.
 * Area 51 Marina
 * Belle Starr Marina
 * Duchess Creek Marina
 * Eufaula Cove Marina
 * Evergreen Marina
 * Lake Eufaula Marina
 * No. 9 Marina

title: Lake Eufaula (Oklahoma)


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Lake Stanley Draper

Lake Stanley Draper is a reservoir in southeast Oklahoma City, United States. It is one of three municipal reservoirs in the city. Principal construction on the reservoir occurred between 1962-1963. Upon completion it was named after the long-time director of the Oklahoma City Chamber of Commerce, Stanley Draper. Located between Midwest Boulevard and Post Road, near I-240, it receives water by pipeline from Atoka Lake and McGee Creek Reservoir.

History
The lake was begun in 1962 to serve as a reservoir for Oklahoma City.

Description
It has a surface area of 2900 acre, an average depth of 34 feet and a maximum depth of 98 feet. The volume is 87296 acre-feet

Recreation
The lake is open for a number of things including, fishing, ATVs or dirt bikes, R.C. airplanes, boating (sailing, Water skiing, and jet skiing). Water skiing is allowed in the main body of the lake, but swimming is prohibited everywhere in the lake. There are four covered fishing piers, primitive campgrounds, picnic grounds, grills and rest rooms.

Maintenance
In March 2010 City of Oklahoma City began work for the Atoka Pump Station Rehabilitation Project (APSRP). During the project 24 new pumps were installed while six others were refurbished along the 100 mi Atoka Pipeline. During that time, the pumps were periodically shut down to allow for installation and refurbishment, which caused lake water levels to drop well below its normal pool depth of 1,187 ft. Because of the low water levels all boating is prohibited, with only authorized personnel allowed on the water. On February 25, 2011, the pipeline was brought back to full service allowing water to be pumped from Lake Atoka to Draper. From February 2011 the lake's water level remained low due to the lack of heavy rainfall because of the then ongoing drought and water usage by residents of Oklahoma City. The City expected that the lake would return to levels high enough to allow recreational use by late fall 2013. In April 2015 following substantial rainfall, the lake reached and passed its pool depth, bringing the lake back to full capacity.

title: Lake Stanley Draper


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Canton Lake (Oklahoma)

Canton Lake is a lake in Blaine and Dewey Counties in Oklahoma, near Longdale and Canton. Its main source of water is the North Canadian River. It is about an hour away from Enid. The lake serves as a municipal water supply reservoir for Oklahoma City, which pays to have water released from the lake for water-supply purposes.

Canton Dam was a 1948 project of the Southwestern Division of the United States Army Corps of Engineers. The earthen structure is 68 ft high and 15,140 ft long at its crest, with a maximum storage capacity of 383,000 acre-feet. The lake has a shoreline of 45 mi. Canton is owned and operated by the Army Corps of Engineers but Oklahoma City retains the storage rights.

The lake is home to several species of fish, including largemouth bass, white bass, channel catfish, crappie, and walleye. Canton has become the primary source of walleye eggs for incubation and stocking of other state lakes. Since 1968, community leaders and local merchants have promoted an annual Walleye Rodeo. The four-day event offers visitors the chance to win cash and other prizes that total over $30,000.

Facilities at the lake include boat ramps, picnic areas, RV and tent campsites, drinking water, group shelters, restrooms, showers, a swimming beach, concession services, and a nature trail.

In early 2013, Oklahoma City officials diverted 30,000 acre-ft of water from Canton Lake to Lake Hefner, to replenish the city's water supply. Later, spring rains replenished the level of that lake, which had to dump water into the North Canadian River to prevent the lake from overflowing. However, the effect was to leave Canton Lake 13 ft below its normal level. This has contributed to an algae bloom.

In April 2016, the lake finally replenished from the 2013 water diversion Oklahoma City made.

In August 2022, Oklahoma City officials have requested a water release from Canton Lake to replenish Lake Hefner. The release is planned to lower lake Canton by about 2 ft and raise Lake Hefner by an equal amount

title: Canton Lake (Oklahoma)


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Bell Cow Lake

Bell Cow Lake (sometimes written as Bellcow) is a reservoir located within the city limits of Chandler, Oklahoma, in a section of the city located to the northwest of its central district, just off Interstate 44 and Oklahoma State Highway 18.

The lake was constructed on Bell Cow Creek for flood control, water supply, recreation, and fish and wildlife purposes. The lake surface covers 1153 acres. Four recreational areas cover another 1000 sqft, offering boating, fishing, swimming, camping, picnicking, and horseback riding. Its overall dimensions are 3.5 miles wide by 1 mile long, and it opened officially in January, 1994.

title: Bell Cow Lake


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Fort Cobb Reservoir

Fort Cobb Reservoir (also called Fort Cobb Lake) is a reservoir located in Caddo County in the U.S. state of Oklahoma. It impounds the waters of Cobb Creek (joining from the west), Lake Creek (joining from the north), and Willow Creek (joining from the northeast). The lake covers approximately 4,000 acre of water and 45 mi of shoreline. Its drainage area is 285 mi2. It was constructed in 1958. The towns of Carnegie, Fort Cobb, and Eakly are located nearby.

Fort Cobb Dam is on Cobb Creek about 5 mi north of Fort Cobb, and roughly 5 mi above the confluence of Cobb Creek with the Washita River. The dam is a zoned earthfill structure containing 3,569,185 cubic yards (2,729,000 m3) of embankment. The crest width is 30 ft, and the crest length is 9,900 ft. The structural height of the dam is 122 ft.

Fort Cobb Reservoir has a total capacity of 143740 acre.ft and covers an area of 5956 acre at top of flood pool level. The uncontrolled morning-glory spillway in the left abutment consists of a concrete intake structure, concrete conduit, and concrete chute and stilling basin.

The Fort Cobb Reservoir is part of the Washita Basin Project of the Bureau of Reclamation, which also includes Foss Reservoir on the Washita River in Custer County, along with numerous small flood-control structures on creeks and streams. Municipal and industrial water is supplied to the city of Anadarko and Western Farmers Electric Cooperative through the Anadarko Aqueduct which begins at the Fort Cobb Reservoir.

Recreation and fish and wildlife
Fort Cobb Reservoir provides over 2,000 acre of land and some 2,300 acre of water surface areas for recreation and includes 1,800 acre of land and 1,800 acre of water surface area for wildlife management. This reservoir provides some 45 mi of shoreline at top of conservation pool. The recreation areas are administered by the Oklahoma Tourism and Recreation Department and the wildlife management area is administered by the Oklahoma Department of Wildlife Conservation. Since reservoir releases are primarily for municipal and industrial demands and flood control, the reservoir does not normally experience drastic drawdowns.

The primary fish species include white and smallmouth bass, channel catfish, walleye, bluegill, bullhead, saugeye and crappie.

The lake offers five RV campgrounds, one RV & Tent campground and four tent campgrounds on the southeast and southwest area of Fort Cobb Lake. Fort Cobb State Park and the wildlife management areas of the lake.

title: Fort Cobb Reservoir


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Konawa Reservoir

Konawa Reservoir (also known as Konawa Lake or Lake Konawa) is a reservoir located in Seminole County, Oklahoma. The lake covers approximately 1350 acre and has a capacity of 23000 acre feet. It is owned by Oklahoma Gas and Electric (OG&E) Company. and was constructed in 1968-70, to provide cooling for a nearby gas-fired electric power generation plant. It impounds Jumper Creek, about 2 miles east of the city of Konawa, Oklahoma.

Description
Konawa Reservoir supplies cooling water for a gas-fired electric power generation plant owned by Oklahoma Gas and Electric (OG&E) Company and located in Seminole County, Oklahoma. The plant has three steam-driven turbine generators and a gas turbine with a combined capacity of 1,534 megawatts (MWe). When the three main steam-driven generators are on-line, the plant must circulate a million gallons of water per minute (GPM) through its exhaust steam condensers.

The reservoir has a surface area of 1350 acre, a shoreline of 20 miles and a rated capacity of 23000 acre.ft. The mean depth is 17 feet and the maximum depth is 49.8 feet. The pool surface elevation is 924 feet above mean sea level. The lake level is maintained by pumping water from the South Canadian River as needed.

Recreation
Rod and reel fishing is allowed at Konawa. State fishing laws apply and a valid fishing license is required. Water skiers and personal watercraft are also allowed to use the lake. Houseboats are prohibited.

Wildlife
In 2003, Konawa ranked first among Oklahoma Lakes larger than 1,000 acres in the production of Largemouth bass. Other species of fish include:Channel Catfish, Flathead Catfish, Hybrid Striped Bass, Sunfish and White Bass.

title: Konawa Reservoir


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McGee Creek Reservoir

McGee Creek Reservoir is a reservoir in Atoka County, Oklahoma. It impounds the waters of McGee Creek and several smaller streams, including Potapo, Panther, Little Bugaboo, Bear, Blue, Mill, and Crooked creeks, all of which are tributaries of Muddy Boggy River. According to the Bureau of Reclamation (BuRec), the reservoir was designed to extend 14 miles up McGee Creek and 9 miles up Potapo Creek when the water is at "conservation level.

McGee Creek Lake is bordered by the McGee Creek Wildlife Management Area, the McGee Creek Natural State Scenic Recreation Area, and McGee Creek State Park. The combined effect of these protected lands is to afford the area the same rural and isolated nature it has always known.

Reservoir
McGee Creek Lake is 17 miles east of Atoka; 18 miles west of Antlers and 3 miles north of Farris, Oklahoma

The reservoir, which filled at the completion of the United States Bureau of Reclamation McGee Dam in 1987, consists of 3810 acre surface area and 64 mi of shoreline. Its pool elevation is 577 ft above sea level and it holds 113,930 acre.ft. At flood stage its pool elevation is 595.5 ft above sea level and its storage capacity rises to 199270 acre.ft. The reservoir has a maximum depth of 116 feet at the dam when the water is at conservation pool level.

Dam and river outlet
The dam is an earth-filled structure that is 1968.5 feet long and 160.7 feet high across McGee Creek. An earthen dike 4800 feet long and 59 feet high, blocks several saddles on the west side of the reservoir rim. A riprap blanket prevents erosion of the upstream sides of both the dam and the dike. The river outlet works located on the east side of the dam release water to McGee Creek under extreme conditions. The works include an intake structure, three conduits (each about 15 ft in diameter), a stilling basin, associated gates and controls. The discharge channel to McGee Creek can pass flows ranging from 6500 ft3 to 50000 ft3 per second.

Municipal water outlet
Water from the lake is routinely pumped to municipal consumers via pipeline. The municipal outlet works has a bypass that diverts 11 cuft directly downstream to McGee Creek. This provides a constant stream of water that is beneficial to marine life. The river outlet works, located on the east side of the dam, handle this function. A separate intake leads to three conduits (each 15 feet diameter), which terminate in a stilling basin, that has a single pipe leading to the three variable-capacity centrifugal discharge pumps. The pumps discharge into a surge tank at the Atoka Lake, 18 miles away, via a concrete pipe that is 5 feet diameter. Other pumps then transfer the water to Oklahoma City.

History
The McGee Creek Project and McGee Creek Authority were established in 1978 to develop and maintain the McGee Creek Reservoir to provide a municipal and industrial water supply for areas in central and southern Oklahoma, including Oklahoma City and Atoka County. Under the direct supervision of superintendent Glen Russell, the authority has operated and maintained the reservoir and associated facilities, including an attached water pipeline, a surge tank, a regulating tank, a maintenance complex, and land easements surrounding these facilities. The U.S. Department of Interior, Bureau of Reclamation owns the reservoir, but has granted McGee Creek Authority ownership title to the project office, aqueduct and appurtenances, and other operation and maintenance related facilities.

title: McGee Creek Reservoir


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Tom Steed Reservoir

Created in 1975, Tom Steed Reservoir is a reservoir in Kiowa County, Oklahoma, 6 mi northwest of the city of Snyder, Oklahoma. The reservoir area was created by damming West Otter Creek and diverting flows of Elk Creek through the Bretch Diversion Canal by Mountain Park Dam. Tom Steed Reservoir is the main feature of the Mountain Park Project of the U.S. Bureau of Reclamation. It provides municipal and industrial water to the cities of Snyder, Altus, and Frederick, as well as the Hackberry Flat Wildlife Management Area.

Dam
Mountain Park Dam is located just upstream of Snyder Dam, on Otter Creek near Mountain Park, Oklahoma. A thin double-curvature concrete arch flanked by concrete thrust blocks, Mountain Park Dam is 535 feet (163 m) in length with a maximum structural height of 133 feet (41 m). This dam and the rolled earth East and West Dike embankments, which extend 10,311 and 13,235 feet (3143 and 4034 m), respectively, form the Tom Steed Reservoir. The reservoir has a total capacity of 117,825 acre.ft, an active capacity of 109,276 acre.ft, and a surface area at the top of conservation pool of approximately 6,400 acres (26 km²). Its elevation is 1407 feet.

Recreation and wildlife
The Oklahoma Tourism and Recreation Department administers 6,100 acres (25 km²) on the east and south shores of the reservoir. Public recreation facilities on the east side include shelters, tables, grills, a comfort station, a boat launching ramp, and a swimming beach. The area south of the dam along Otter Creek offers picnic facilities and a bridge across the creek which leads to a nature trail through large cottonwood, ash, elm, walnut, and pecan trees.

The Oklahoma Department of Wildlife Conservation administers 5,150 acres (21 km²) of the west and north side of the reservoir area. Waterfowl and dove are plentiful, and other upland game species are increasing as more food and cover are developed. An extensive tree and shrub planting program continues to increase wildlife habitat. The reservoir is one of the best fishing areas in southwest Oklahoma, offering catfish, crappie, largemouth black bass, and other varieties.

Great Plains State Park is located on the shore of Tom Steed Reservoir.

title: Tom Steed Reservoir


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Wes Watkins Reservoir

Wes Watkins Reservoir is a reservoir located in Pottawatomie County in central Oklahoma, United States, between Oklahoma City and Shawnee (in the center of McLoud). Its primary use is recreation, especially camping and fishing.

Wes Watkins Reservoir was opened to the public in August 1999 and is considered a relatively young reservoir. The 1142 acre lake is operated by the City of McLoud as of July 1, 2010. It was formerly managed by Pottawatomie County Development Authority.

The reservoir was named in honor of former Oklahoma Congressman Wes Watkins. It was initially known as North Deer Creek Lake.

The Shawnee city commissioners approved the transfer of Wes Watkins Reservoir recreational operations and management to the city of McLoud, beginning July 1, 2010.

Its drainage area is 38.5 square miles. According to a report by Camp, Dresser & McKee (CDM), the normal capacity of the reservoir is 13993 acre.ft.

title: Wes Watkins Reservoir


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Random number generator attack

The security of cryptographic systems depends on some secret data that is known to authorized persons but unknown and unpredictable to others. To achieve this unpredictability, some randomization is typically employed. Modern cryptographic protocols often require frequent generation of random quantities. Cryptographic attacks that subvert or exploit weaknesses in this process are known as random number generator attacks.

A high quality random number generation (RNG) process is almost always required for security, and lack of quality generally provides attack vulnerabilities and so leads to lack of security, even to complete compromise, in cryptographic systems. The RNG process is particularly attractive to attackers because it is typically a single isolated hardware or software component easy to locate. If the attacker can substitute pseudo-random bits generated in a way they can predict, security is totally compromised, yet generally undetectable by any upstream test of the bits. Furthermore, such attacks require only a single access to the system that is being compromised. No data need be sent back in contrast to, say, a computer virus that steals keys and then e-mails them to some drop point.

Human generation of random quantities
Humans generally do poorly at generating random quantities. Magicians, professional gamblers and con artists depend on the predictability of human behavior. In World War II German code clerks were instructed to select three letters at random to be the initial rotor setting for each Enigma machine message. Instead some chose predictable values like their own or a girlfriend's initials, greatly aiding Allied breaking of these encryption systems. Another example is the often predictable ways computer users choose passwords (see password cracking).

Nevertheless, in the specific case of playing mixed strategy games, use of human gameplay entropy for randomness generation was studied by Ran Halprin and Moni Naor.

Software RNGs
Just as with other components of a cryptosystem, a software random number generator should be designed to resist certain attacks. Some attacks possible on a RNG include (from ):

 * Direct cryptanalytic attack: when an attacker obtained part of the stream of random bits and can use this to distinguish the RNG output from a truly random stream.
 * Input-based attacks: modify the input to the RNG to attack it, for example by "flushing" existing entropy out of the system and put it into a known state.
 * State compromise extension attacks: when the internal secret state of the RNG is known at some time, use this to predict future output or to recover previous outputs. This can happen when a generator starts up and has little or no entropy (especially if the computer has just been booted and followed a very standard sequence of operations), so an attacker may be able to obtain an initial guess at the state.

Hardware RNGs
A number of attacks on hardware random number generators are possible, including trying to capture radio-frequency emissions from the computer (obtaining hard drive interrupt times from motor noise, for example), or trying to feed controlled signals into a supposedly random source (such as turning off the lights in a lava lamp or feeding a strong, known signal into a sound card).

RNG subversion
Subverted random numbers can be created using a cryptographically secure pseudorandom number generator with a seed value known to the attacker but concealed in the software. A relatively short, say 24 to 40 bit, portion of the seed can be truly random to prevent tell-tale repetitions, but not long enough to prevent the attacker from recovering, say, a "randomly" produced key.

Random numbers typically go through several layers of hardware and software before they are used. Bits may be generated in a peripheral device, sent over a serial cable, collected in an operating system utility and retrieved by a system call. The subverted bits can be substituted at any point in this process with little likelihood of detection.

A hardware circuit to produce subverted bits can be built on an integrated circuit a few millimeters square. The most sophisticated hardware random number generator can be subverted by placing such a chip anywhere upstream of where the source of randomness is digitized, say in an output driver chip or even in the cable connecting the RNG to the computer. The subversion chip can include a clock to limit the start of operation to some time after the unit is first turned on and run through acceptance tests, or it can contain a radio receiver for on/off control. It could be installed by the manufacturer at the behest of their national signals intelligence service, or added later by anyone with physical access. CPU chips with built-in hardware random number generators can be replaced by compatible chips with a subverted RNG in the chips' firmware.

Defenses

 * Mix (with, for example, xor) hardware generated random numbers with the output of a good quality stream cipher, as close to the point of use as possible. The stream cipher key or seed should be changeable in a way that can be audited and derived from a trustworthy source, e.g. dice throws. The Fortuna random number generator is an example of an algorithm which uses this mechanism.
 * Generate passwords and passphrases using a true random source. Some systems select random passwords for the user rather than let users propose their own.
 * Use encryption systems that document how they generate random numbers and provide a method to audit the generation process.
 * Build security systems with off the shelf hardware, preferably purchased in ways that do not reveal its intended use, e.g. off the floor at a large retail establishment. From this perspective, sound cards and webcams may be a better source of randomness than hardware made for that purpose.
 * Maintain complete physical control over the hardware after it has been purchased. The hardware should at one place or location and need no other transmission to a peer-to-peer hardware. Attacks are on the line in the network not the hardware itself.

Designing a secure random number generator requires at least as high a level of care as designing other elements of a cryptographic system.

Predictable Netscape seed
Early versions of Netscape's Secure Sockets Layer (SSL) encryption protocol used pseudo-random quantities derived from a PRNG seeded with three variable values: the time of day, the process ID, and the parent process ID. These quantities are often relatively predictable, and so have little entropy and are less than random, and so that version of SSL was found to be insecure as a result. The problem was reported to Netscape in 1994 by Phillip Hallam-Baker, then a researcher in the CERN Web team, but was not fixed prior to release. The problem in the running code was discovered in 1995 by Ian Goldberg and David Wagner, who had to reverse engineer the object code because Netscape refused to reveal the details of its random number generation (security through obscurity). That RNG was fixed in later releases (version 2 and higher) by more robust (i.e., more random and so higher entropy from an attacker's perspective) seeding.

Microsoft Windows 2000/XP random number generator
Microsoft uses an unpublished algorithm to generate random values for its Windows operating system. These random quantities are made available to users via the CryptGenRandom utility. In November 2007, Leo Dorrendorf et al. from the Hebrew University of Jerusalem and University of Haifa published a paper titled Cryptanalysis of the Random Number Generator of the Windows Operating System. The paper presented serious weaknesses in Microsoft's approach at the time. The paper's conclusions were based on disassembly of the code in Windows 2000, but according to Microsoft applied to Windows XP as well. Microsoft has stated that the problems described in the paper have been addressed in subsequent releases of Windows, which use a different RNG implementation.

Possible backdoor in Elliptic Curve DRBG
The U.S. National Institute of Standards and Technology has published a collection of "deterministic random bit generators" it recommends as NIST Special Publication 800-90. One of the generators, Dual_EC_DRBG, was favored by the National Security Agency. Dual_EC_DRBG uses elliptic curve technology and includes a set of recommended constants. In August 2007, Dan Shumow and Niels Ferguson of Microsoft showed that the constants could be constructed in such a way as to create a kleptographic backdoor in the algorithm. In September 2013 The New York Times wrote that "the N.S.A. had inserted a back door into a 2006 standard adopted by N.I.S.T... called the Dual EC DRBG standard", thereby revealing that the NSA carried out a malware attack against the American people. In December 2013, Reuters reported that documents released by Edward Snowden indicated that the NSA had paid RSA Security $10 million to make Dual_EC_DRBG the default in their encryption software, and raised further concerns that the algorithm might contain a backdoor for the NSA. Due to these concerns, in 2014, NIST withdrew Dual EC DRBG from its draft guidance on random number generators, recommending "current users of Dual_EC_DRBG transition to one of the three remaining approved algorithms as quickly as possible."

MIFARE Crypto-1
Crypto-1 is a cryptosystem developed by NXP for use on MIFARE chips. The system is proprietary and originally the algorithm has not been published. Upon reverse engineering of the chip, researchers from the University of Virginia and the Chaos Computer Club found an attack on Crypto-1 exploiting a poorly initialized random number generator.

Debian OpenSSL
In May 2008, security researcher Luciano Bello revealed his discovery that changes made in 2006 to the random number generator in the version of the OpenSSL package distributed with Debian Linux and other Debian-based distributions, such as Ubuntu, dramatically reduced the entropy of generated values and made a variety of security keys vulnerable to attack. The security weakness was caused by changes made to the openssl code by a Debian developer in response to compiler warnings of apparently redundant code. This caused a massive worldwide regeneration of keys, and despite all attention the issue got, it could be assumed many of these old keys are still in use. Key types affected include SSH keys, OpenVPN keys, DNSSEC keys, key material for use in X.509 certificates and session keys used in SSL/TLS connections. Keys generated with GnuPG or GNUTLS are not affected as these programs used different methods to generate random numbers. Keys generated by non-Debian-based Linux distributions are also unaffected. The weak-key-generation vulnerability was promptly patched after it was reported, but any services still using keys that were generated by the old code remain vulnerable. A number of software packages now contain checks against a weak key blacklist to attempt to prevent use of any of these remaining weak keys, but researchers continue to find weak key implementations.

PlayStation 3
In December 2010, a group calling itself fail0verflow announced recovery of the elliptic curve digital signature algorithm (ECDSA) private key used by Sony to sign software for the PlayStation 3 game console. The attack was made possible because Sony failed to generate a new random nonce for each signature.

RSA public key factoring
An analysis comparing millions of RSA public keys gathered from the Internet was announced in 2012 by Lenstra, Hughes, Augier, Bos, Kleinjung, and Wachter. They were able to factor 0.2% of the keys using only Euclid's algorithm. They exploited a weakness unique to cryptosystems based on integer factorization. If n = pq is one public key and n′ = p′q′ is another, then if by chance p = p′, then a simple computation of gcd(n,n′) = p factors both n and n′, totally compromising both keys. Nadia Heninger, part of a group that did a similar experiment, said that the bad keys occurred almost entirely in embedded applications, and explains that the one-shared-prime problem uncovered by the two groups results from situations where the pseudorandom number generator is poorly seeded initially and then reseeded between the generation of the first and second primes.

Java nonce collision
In August 2013, it was revealed that bugs in the Java class SecureRandom could generate collisions in the k nonce values used for ECDSA in implementations of Bitcoin on Android. When this occurred the private key could be recovered, in turn allowing stealing Bitcoins from the containing wallet.

title: Random number generator attack