M J Lombardero

M Alonso-Rodriguez

E P Roca Posada

Enric Frago
email: enric.frago@uv.es.

Juli Pujade-Villar

Miguel Guara

Jesús Selfa

Gadir Nouri Ganbalani

Sattar Zeinali

Davoud Shamohammadi

S12: Forest entomology III. Room Brussels Forest management and pest dynamics

Highly productive plantations in Southern Europe are characterized by intensive sylviculture and the introduction of fast growing trees to increase productivity. Sylvicultural practises are common tools to improve yield but also stand condition and tree vigour. We tested how thinning affects the population dynamics of the two major pests in the area, bark beetles borers and the defoliator Processionary moth. The study was carried out within 4 thinned and 4 unthinned plots of the native species (Pinus pinaster Ait.) and 3 thinned and 3 unthinned plots of an introduced pine (Pinus radiata D.Don), located in sites with similar characteristics. Bark beetles showed a strong preference for the native species. Both abundance and diversity were much higher in stands of P. pinaster, both as measured by funnel trap captures and by study of trees under attack. There was no effect of thinning on the abundance and diversity of the population flying within plots, but there was a strong effect of thinning on the number of trees under attack located mainly in unthinned plots. Thinning treatments did not have an effect on the abundance or diversity of natural enemies, but again the native stands showed a significantly greater abundance of natural enemies and almost twice more species. The native stands were better defended against bark beetles with higher constitutive resin, but there was no effect of thinning on resin flow. Finally the native species seems to be also a more suitable tree for bark beetles than the exotic and the thinning treatments had a positive effect on the nutritional quality of phloem. Larvae of the Processionary moth weigh more and survive better when feeding on P. radiata, but there was no effect of thinning. N contents were higher in P. radiata needles, independently of the treatment. In summary, borers and defoliators seem to have different preferences, but native stands seem generally better defended against native pests. In addition bark beetle populations within stands of native trees are subject to stronger controls by natural enemies.

Life table studies have been an essential tool for the comprehension of insect population dynamics. However, they are methodologically biased by a primary focus on mortality factors, especially natural enemies. Thus, life table studies may relegate important mortality sources to the "unknown" or "residual" mortality categories. To overcome this limitation life tables may be complemented by combining them with other approaches. The aim of this study is to provide insights into browntail moth Euproctis chrysorrhoea L. (Lepidoptera: Lymantriidae) local outbreaks by combining life table data and statistical modelling. First, we have compared E. chrysorrhoea population density, mortality dynamics, net reproductive rate and reproductive potential in two different Mediterranean habitats (i.e. coastal and inland). Second, by means of generalized additive modelling (GAM models), we have investigated the relationship of reproductive potential as well as residual mortality in the life tables with several variables likely to influence E. chrysorrhoea population dynamics. Our results suggest that local outbreaks are more likely in coastal habitats where higher mortality was compensated by higher reproductive potential. GAMs revealed that residual mortality increased with E. chrysorrhoea population density non-linearly, and that realized fecundity was negatively and linearly related to extremely hot temperatures. Results may be useful for forecasting E. chrysorrhoea local outbreaks.

Diversity of Pemphigus galls on the Lombardy black poplar (Populus nigra 'Italica') Katalin Tuba, Ferenc Lakatos

University of West-Hungary, Institute of Silviculture and Forest Protection, 9401 Sopron, PoB. 132., Hungary, tubak@emk.nyme.hu Populus nigra 'Italica' trees have been planted under different environmental conditions. Their genetic uniformity represents a unique opportunity to study the local effects on a particular genotype. Most of the Pemphigus species are associated with black poplar (Populus nigra), causing various types of galls. In our study we have examined the diversity, the frequency and the life-strategy of Pemphigus species living on Populus nigra 'Italica' trees in north-western part of Hungary. We investigated the effect of the local environmental conditions (biogeographical species pools, site conditions, surrounding vegetation) on the diversity of Pemphigus species under three different conditions: urban, village and rural environment. Altogether eight Pemphigus species were recorded. The dominant species was P. spyrothecae; however the frequency varied strongly among the sites. The less frequent species was P. borealis. These gall makers showed higher species diversity in the village sites than the urban and rural sites. Pemphigus species have different life strategies which can help to adapt to the various conditions. Based on the life-strategy eight species were classified into four groups. These groups were compared on the different survey sites.

Invading pine processionary moths benefit from escape from natural enemies Charles-Edouard Imbert, Alain Roques INRA, UR 633 Zoologie Forestière, F-45075 Orléans, France Under temperate latitudes, low temperature is usually a key factor constraining the distribution of insects species through minimal thresholds required for survival and development. Thus, range shift is one of the striking observed effects of global warming on a number of cold sensitive species. However, the consequences of such range shifts on interspecific interactions, especially with natural enemies, are largely unexplored. The winter-developing pine processionary moth, Thaumetopoea pityocampa (Lepidoptera, Notodontidae), occurs around the Mediterranean Basin and expanded considerably its range distribution towards higher latitudes and altitudes over the last two decades. This range expansion is clearly associated with better winter survival and enhanced feeding activity related to climate warming. We tested whether the egg parasitoids actually tracked the expanding host populations. Egg parasitism rates and structure of egg batches were surveyed along three transects from the moth endemic area to the front area in several regions of France. Observations were made on a total of 71757 eggs from 426 egg batches. Parasitism rates and structure of egg batches significantly differed along the expansion transects. Total parasitism decreased from the endemic area to the front area whilst the mean number of eggs per batch increased. The degree of polyphagy also influenced the species-specific response of egg parasitoids. These results suggest that expanding populations may escape from natural enemies for a given period at least. With a lower parasitism rate combined to more eggs laid, the colony size might be greater and could provide higher winter survival enhancing the expansion speed.

Increasing defoliator pressure on the Hungarian Forests Gy. Csóka, A. Hirka, A. Koltay, L.G. Janik, L. Szőcs

Department of Forest Protection, Hungarian Forest Research Institute

The analysis of the Hungarian meteorological data shows increasing frequency and severity of droughts in Hungary during the last 50 years. In the same time both the total insect damage and the insect defoliation recorded in the Hungarian forests also show increasing trend. The last outbreak of Lymantria dispar peaked in 2004 with 212,000 ha are damaged. This damage area is more than 6-fold larger than the earlier maximum recorded in 1994. On top of the severely increased damage area its damage also expanded vertically causing considerable damage in montane beech stands. Yearly damage area of both Euproctis chrysorrhoea and Thaumetopoea show steadily increasing trends in the last decades. On top of these "classic" species of defoliators (earlier not known as pest) are emerging year by year. Reasons and consequences of these trends are discussed in the presentation.

Studies on tolerance resistance mechanism of poplar clones and willow species against the willow and poplar lace-bug, Monosteira unicostata (Mulsant & Rey) (Hemiptera: Tingidae), under natural conditions Ali Ahadiyat 1 , Seyed Ebrahim Sadeghi 2 , Hadi Ostovan 3 , Saeid Moharramipour Willow and poplar lace-bug, Monosteira unicostata, is considered as an important pest of willow and poplar species and clones in Iran. The pest feeds on leaves by sap sucking and damages the chlorophyll leading to their yellowing and finally dropping after heavy infestation. During the Spring 2008, tolerance mechanisms of five poplar clones, including Populus alba 44.9, P. deltoides missouriensis, P. euramericana grandis, P. e. marilandica and P. nigra 56.53, and four willow species, including Salix acmophylla, S. alba, S. elbursensis and S. fragilis, were evaluated under natural conditions. Four young branches with 50 cm length, each with 4-5 similar leaves, were chosen from each poplar clone and willow species, as replications. After releasing 10 pairs of male and female bugs in each replication, the branch was completely surrounded by net cloth. One young branch with similar characters was also chosen in each clone or species as control. All infested and control stems were taken and moved to the laboratory and leaf yellowing surfaces were measured using Leaf Area Meter. Thereafter, leaf Functional Loss Potential (FLP) was computed and the data was statistically analyzed in which significant differences (P<0.05) were observed between the genera Populus and Salix based on FLP. So, willow had less tolerability than poplar trees and was more susceptible. Among the willow species, S. alba and S. acmophylla had the maximum FLP and were considered as susceptible species, respectively, and S. elbursensis had more tolerability than other willow species. Among the poplar clones, P. a. 44.9 and P. d. missouriensis had maximum and minimum FLP and were considered as the most susceptible and most resistant clones, respectively. S13: Aquatic insects III.

Room Rome

Diel and seasonal dispersal of aquatic Coleoptera and Heteroptera species -Are the diel dispersal patterns species-or environment-dependent? Zoltán Csabai 1 , Pál Boda 2 , Ildikó Szivák 1 , Zoltán Kálmán 1 1 University of Pécs, Department of General and Applied Ecology, Ifjúság útja 6., H-7624 Pécs, Hungary 2 Trans-Tisza Region Environmental, Nature Protection and Water Inspectorate, Hatvan utca 16., H-4025 Debrecen, Hungary

Both the daily and the seasonal dispersal dynamics of aquatic Coleoptera and Heteroptera species were studied in 2005 under various environmental circumstances by monitoring number of species and number of individuals of insects attracted to highly and horizontally polarizing shiny black plastic sheets laid on the ground. During our weekly samplings insects landed on three 9×3 meter sized test surfaces were collected continuously by manual sampling and using insect aspirators. Samples were separated hourly and the environmental variables (e.g. wind speed, air temperature, air pressure, relative air humidity, light intensity and indirectly polarotactic detectability of water surfaces), possibly affecting the dispersal, were continuously registered. During the sampling periods (30 days, 24 hours every day) more than 45000 individuals were captured, belonging to 86 (69+17) aquatic Coleoptera and Heteroptera taxa. Species and/or species groups could be characterized by different diel and seasonal dispersal activity patterns. We observed at least 3 seasonal and 4 diel basic types and several remarkably different subtypes of flight activity. Our results suggest that diel flight activity patterns are not species-dependent, diel patterns could be changed between seasons: one and the same species shows extreme and statistically significant differences in diel flight pattern among spring, summer or autumn periods because of different environmental circumstances.

Dispersal in aquatic beetles -effects of environmental variability and species and individual traits Jan Klečka¹, David Boukal²

¹

  Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic ² Department of Theoretical Ecology, Biology Centre of the Academy of Sciences of the Czech Republic, Institute of Entomology, České Budějovice, Czech Republic We studied the flight activity of aquatic beetles in a semipermanent wetland using a light trap in 2002-2006. Our goal was to measure the effects of environmental conditions (temperature, weather conditions and water level fluctuations), sex, maturity and body size on the flight activity of aquatic beetles. Flight activity (individuals per night) was highest in summer and major peaks coincided with periods of rapid desiccation of the wetland. No flight occurred when the temperature


Faustmann Rotation and Aquaculture in the presence of an epidemic risk Patrice Loisel * †

Introduction

For the management of natural resources, the first question that arises is : what is the optimal duration of cycle production. This is the case both in forestry, aquaculture, production of renewable resources. In the case where a calculation method to predict earnings for various terms of the cycle is available, Faustmann [START_REF] Faustmann | Berechnung des Wertes welchen Waldboden sowie noch nicht haubare Holzbestände für die Weldwirtschaft besitzen[END_REF] proposed a formalism based on the expected discounted yield. Many authors have successively improved or reformulated the method, Ohlin [START_REF] Ohlin | Concerning the question of the rotation period in forestry[END_REF], Pearse [START_REF] Pearse | The optimal forest rotation[END_REF]. Clark [START_REF] Clark | Mathematical Bioeconomics[END_REF] has applied this method to natural resources. Bjorndal [START_REF] Bjorndal | Optimal Harvesting of Farmed Fish[END_REF] analyzes the optimal duration of farmed fish. Arneson [START_REF] Arneson | Optimal Feeding Schedules and Harvesting Time in Aquaculture[END_REF] studied optimal feeding and harvest time with respect to fish-growth function. Heaps [START_REF] Heaps | The optimal feeding of farmed fish[END_REF] analysed optimal feeding schedules and harvesting policies for farmed fish. The preceeding works are characterized by the absence of risk of destructive events. The risk of destruction has been introduced to forest stands by Martell [START_REF] Martell | The optimal rotation of a flammable forest stand[END_REF] and Routledge [START_REF] Routledge | Effect of potential catastrophic mortality and other unpredictable events on optimal forest rotation policy[END_REF] in discrete time. Thereafter, Reed [START_REF] Reed | The Effects of the Risk of Fire on the Optimal rotation of a Forest[END_REF] has studied the optimal forest rotation in continuous time with the risk of fire. Thorsen and Helles [START_REF] Thorsen | Optimal stand management with endogenous risk of sudden destruction[END_REF] maximized a not discounted criterion taking into account the risk and using a population model. Most of the work on Faustmann rotation and in particular the study of Reed [START_REF] Reed | The Effects of the Risk of Fire on the Optimal rotation of a Forest[END_REF] are developed in the context of forestry but are not specific to forestry and can be applied to the production of renewable resources. In the context of random prices in aquaculture Guttormsen [START_REF] Guttormsen | Faustmann in the Sea -Optimal Rotation Time in Aquaculture[END_REF] studies a method based on dynamic programming.

For the absence of risk of epidemic events all the production cycles are carried out to the same term. When the risk of destructive event exists and is taken into account, the authors cited above assume that the operator systematically decides to interrupt the current cycle and begin a new cycle. This is fully justified in the case of severe epidemic. In the case of an epidemic of limited impact on mortality, to the first question about the optimal term a second question is added : should we interrupt the current cycle and begin a new cycle or is it better to continue the current cycle ? If there are alternatives, what is the criterion to choose ? To fulfill this goal, we define a criterion for choice. We consider an averaged fish model, inspired by the models of Hannesson [START_REF] Hannesson | Optimal thinning of a year-class with density-dependent growth[END_REF] and Heaps [START_REF] Heaps | Density dependent growth and the culling of farmed fish[END_REF]. For specific decisions and thus specific criteria, we study two particular cases. In the first case, the operator systematically interrupts the cycle in case of a epidemic event, we generalize the results obtained by Reed [START_REF] Reed | The Effects of the Risk of Fire on the Optimal rotation of a Forest[END_REF] under less restrictive assumptions. We show that the results obtained in [START_REF] Reed | The Effects of the Risk of Fire on the Optimal rotation of a Forest[END_REF] are valid under the assumption that the operator does not harvest during the production cycle. The proposed method takes into account intermediate harvesting. In the second case, the operator continues the cycle even in case of epidemic events (which makes sense if the epidemic is minor) and we deduce the corresponding expected discounted yield. In a first part, we determine the Faustmann value without or with the presence of risk. In a second part, for a fixed rotation period. we compare the results of the optimization with respect the intermediate culling in the absence and presence of risk. Then we deduce the impact of the presence of a risk for aquacultural system. In a third part, we optimize the rotation period and the culling.

The Faustmann value

In the first part we study the Faustmann value without the risk of epidemic event through a model of population dynamics. Then we study the same Faustmann value with the risk of epidemic event.

Without the risk of epidemic event

We first consider an aquacultural system without the presence of risk of epidemic event. The study of this case will allow us to define a benchmark management of the system.

For a rotation period T , a culling h(.) and a feeding f (.) the Faustmann value W 0 (up to a constant c 1 ) is the discounted value of cutting incomes net cost of start-up :

W 0 = +∞ i=1 (V(h(.), f (.), T ) -c 1 )e -iδT = (V(h(.), f (.), T ) -c 1 )e -δT 1 -e -δT = V(h(.), f (.), T ) -c 1 e δT -1
where V(h(.), f (.), T ) is the income generated by the cutting at time T and c 1 is the cost of start-up. V(h(.), f (.), T ) is by definition the sum of the culling income on period [0, T ] and the income at final rotation period T .

The Faustmann value can also be interpreted as, W 0 is the instantaneous value of income in time T discounted at the initial time and is solution of :

W 0 = (W 0 + V(h(.), f (.), T ) -c 1 )e -δT
The population dynamic model To take into account the culling in the calculation of the Faustmann value, i.e. to express V(h(.), f (.), T ), we introduce a model of population dynamics. The considered model is an average fish model : the state variables are the number n of fishes and the weight w. The evolution of these two variables is governed by the system of ordinary differential equations :

dn(t) dt = -(m(t) + h(t))n(t) dw(t) dt = G(f (t), n(t), w(t))
where m(.) is the natural mortality, G(., ., .) is the possibly density dependent growth function : individual fish-growth may depends on the fish density n(t). f (t) is the amount of feed per fish per week.

The net income

Once chosen the model of population dynamics we can express the total income. Total income V(h(.), f (.), T ) for fixed culling h(.) and fixed feeding f (.) is the sum of the culling income net the feeding and fixed costs H(h(.), f (.), T ) on the period [0, T ] and the final income V 0 (T ) :

V(h(.), f (.), T ) = H(h(.), f (.), T ) + V 0 (T )
The culling income net the feeding and the fixed costs H(h(.), f (.), t) on [0, t] actualized to time t are :

H(h(.), f (.), t) = t 0 [p(w(u))h(u)n(u) -sf (u)n(u) -k]e δ(t-u) du
where n(.) and w(.) are solutions of the dynamic model, s is the feeding costs and k fixed costs.

Calculation of the Faustmann value

Finally the Faustmann value is given by :

W 0 = V(h(.), f (.), T ) -c 1 e δT -1 with : V(h(.), f (.), T ) = T 0 [(p(w(u))h(u) -sf (u))n(u) -k]e δ(T -u) du + V 0 (T )
The maximal value of the Faustmann value for a fixed f (.) is obtained by solving the problem :

(P F 0 ) : max h(.),T V(h(.), f (.), T ) -c 1 e δT -1
The maximization of the Faustmann value W 0 with respect to the culling h(.), the feeding f (.) and the rotation period T can be decomposed in two steps : first we maximize V(h(.), f (.), T ) with respect to h(.) : and f (.

) : U 0 (T ) = max h(.),f (.) V(h(.), f (.), T ) then we maxi- mize U 0 (T ) -c 1 e δT -1
with respect to T with U 0 (T ) resulting from the first step.

In the presence of risk of epidemic event

We suppose that epidemic events occur in a Poisson process i.e. that epidemic events occur independently of one another, and ramdomly in time.

The distribution of the epidemic event time is an exponential with mean 1 λ : F (x) = 1-e -λx where λ is the expected number of epidemic events per unit time. No assumption is made on the type of epidemic events. We assume that θ t is the proportion of survival fishes following a epidemic event. We define the expectations

α(t) = E(θ t ) ≤ 1.
When the risk of epidemic event exists and is taken into account, in the literature, the authors classically assume that the operator systematically decides to interrupt the current cycle and begin a new cycle. This is fully justified in the case of severe epidemic. In the case of an epidemic of limited impact on mortality, to the first question about the optimal term a second question is added : should we interrupt the current cycle and begin a new cycle or is it better to continue the current cycle ? If there are alternatives, what is the criterion to choose ? To fulfill this goal, we define a possible criterion for choice based on a function z of θ t ? We assume z increasing with 0 ≤ z(θ) ≤ 1 . We choose a level z 0 such that, in the case of epidemic event :

-if z(θ) < z 0 (severe epidemic), we decide to interrupt the current cycle and begin a new cycle.

-if z(θ) > z 0 (minor epidemic), we decide to continue the cycle.

It is also possible to suppose that z depends on the survival fish at the date of the epidemic event.

Here, we study two particular cases. In the first case, the operator systematically interrupts the cycle in case of a epidemic event (z 0 > 1). In the second case, the operator continues the cycle even in case of epidemic events (which makes sense if the epidemic is minor) (z 0 < 0).

In case of epidemic event, the cycle is interrupt

For a rotation period T , a fixed culling h(.) and a fixed feeding f (.), the Faustmann value W 0 is the actualized value at initial time of the sum of two terms. The first one is the sum of the Faustmann value and the expectation V 1 (h(.), f (.), t) of the total income V(h(.), f (.), θ, t) for the period [0, t] in case of a epidemic event at time t. The second one is the sum of the Faustmann value and the total income V(h(.), f (.), T ) for the period [0, T ] in case of no epidemic event.

V(h(.), f (.), θ, t) is the sum of the culling income net the feeding and fixed costs H(h(.), f (.), t) during [0, t] actualized at time t and the final income V F (θ, t) at time t. The final income V F (θ, t) is assumed proportional to the final income without risk of epidemic event V 0 (T ) and is given by : V F (θ, t) = θV 0 (t). Then the total income is : V(h(.), f (.), θ, t) = H(h(.), f (.), t) + θV 0 (t). From definition of α we deduce the final income expectation :

V 1 (h(.), f (.), t) = E(V(h(.), f (.), θ, t)) = H(h(.), f (.), t) + α(t)V 0 (t)

Calculation of the Faustmann value

From (1) and expression of V 1 (h(.), f (.), t) we deduce that, in the presence of the risk of epidemic event the Faustmann value is given by :

W 0 = δ + λ δ V λ (h(.), f (.), T ) -c 1 e (δ+λ)T -1 - λ δ (c 1 + c 2 )
As in the case without risk, we find that the Faustmann value can be deduced from the income V λ (h(.), f (.), T ). The parameter δ is replaced by δ + λ. The major difference is the following : V 1 (T ) is not as in the case without risk the total income but a modified expression of the income V λ (h(.), f (.), T ). This difference is reflected by the substitution in the cases without risk of term H(h(.), f (.), T ) by a term H λ (h(.), f (.), T ), or even more precise replacing p(w(t))h(t)n(t) -sf (t)n(t) -k by [p(w(t))h(t)n(t) -sf (t)n(t) -k + λα(t)V 0 (t)]e λ(T -t) .

The maximal value of the Faustmann value is obtained by solving :

(P F 1 ) : max h(.),T W 0 = δ + λ δ V λ (h(.), f (.), T ) -c 1 e (δ+λ)T -1 - λ δ (c 1 + c 2 )
As in the case without risk, the maximal value of the Faustmann value with respect to the culling h(.), the feeding f (.) and the rotation period T can be decomposed in two steps : first we maximize V λ (h(.), f (.), T ) with respect to h(.) and f (.) : U λ (T ) = max h(.),f (.)

V λ (h(.), f (.), T )

then we maximize δ + λ δ U λ (T ) -c 1 e (δ+λ)T -1 - λ δ (c 1 + c 2 )
with respect to T with U λ (T ) resulting from the first step.

In case of epidemic event, the cycle is not interrupt

The Faustmann value is obtained by considering the value without risk but calculated with the expected number of survival fish.

3 Optimisation for a fixed rotation period T and a fixed feeding f

We first consider the limiting case of no density dependent growth which will be used as a reference in the case study of density dependent growth.

Without risk of epidemic event

Let us consider the case with fixed feeding f . In this case the evolution of the fish-weight w does not depend of a control.

We study the maximization of the Faustmann value with respect to culling h(.) for a fixed rotation period T :

(S 0 ) max h(.) V(h(.), f (.), T ) = T 0 [(p(w(t))h(t) -sf (t))n(t) -k]e δ(T -t) dt + V 0 (T ) with the constraint 0 ≤ h(t) ≤ h.
Assume that the final income is given by : V 0 (n, w) = p(w)n. From the no density dependence of the individual growth, p(w(t)) is independent of the cullings and only depends on t. Then we define R(t) = p(w(t)). We denote the function π 0 :

π 0 (t) = R (t) -(δ + m(t))R(t) - sf (t).
Applying the maximum Pontryagin Principle to the problem P m,0 we can deduce the optimal culling :

-if π 0 (T ) ≥ 0 then h * ≡ 0 in the vicinity of T -if π 0 (T ) < 0 then h(t) = h in the vicinity of T .

In the presence of risk of epidemic event

In case of epidemic event, the cycle is interrupt

We study the maximization of the Faustmann value with respect to culling h(.) for a fixed rotation period T and a fixed feeding f (.) :

(S 1 ) V λ (h(.), f (.), T ) = max h(.) H λ (h(.), f (.), T ) + V 0 (T ) with the constraint 0 ≤ h ≤ h.
Using the expression of V 0 (T ) we deduce that, compared to the case without risk, p(w(t))h(t)sf (t) is replaced by [p(w(t))h(t)-sf (t)+λα(t)p(w(t))]e λ(T -t) in presence of risk of epidemic event. Thus we deduce that, for the fixed rotation period T , the optimization differs and depends explicitly on λ and α. So we will pay attention to the consequence for the aquacultural practice.

We consider, as in the case without risk, a non density dependent growth for the fishes to facilitate the comparaison.

Let denote the function π 1 : π 1 (t) = R (t)-(λ(1-α(t))+δ +m(t))R(t)-sf (t). Applying the maximum Pontryagin Principle to the problem P m,λ , we deduce the optimal culling :

-if π 1 (T ) ≥ 0 then h * ≡ 0 in the vicinity of T -if π 1 (T ) < 0 then h(t) = h in the vicinity of T 3.2.

In case of epidemic event, the cycle is not interrupt

We study the maximization of the Faustmann value with respect to culling h(.) for a fixed rotation period T .

From the expression of the expected of survival fish N (t) :

N (t) = n(0)e - R t 0 (m(u)+h(u)+λ(1-α(u)))du ,
applying the maximum Pontryagin Principle to the problem P m+λ(1-α),0 we can deduce the optimal culling :

-if π 1 (T ) ≥ 0 then h * ≡ 0 in the vicinity of T -if π 1 (T ) < 0 then h(t) = h in the vicinity of T .

Comparaison : without and with presence of risk

By comparing the three propositions, for the optimal solution in the vicinity of rotation period, the natural mortality m(t) in the case without risk is replaced by the mortality due to events m(t) + λ(1 -α(t)) in the presence of risk. It is equivalent also, from a mathematical point of view, to replace the fixed discount rate δ by the variable discount rate δ + λ(1 -α(t)) in the previous problem.

By comparing the results of the two propositions we deduce that, for a fixed rotation period T , it is usually best to do culling at least at the end of the period in the presence of risk. From π 1 (t) = π 0 (t)-λ(1-α(t))R(t), we deduce that even if h ≡ 0 in the unrisky case, for sufficently large value of λ(1 -α(T )), h = h in the vicinity of T .

Comparing the results of the two proposals is permitted if the rotation periods are identical. If we consider the maximization problem, with respect to the rotation period, the rotation periods have no reason to be the same. In that case the comparison is not permitted and only simulations can allow us to compare the respective culling. We will therefore perform simulations.

4 Optimization with respect to the rotation period T

We now consider the case where individual growth is density dependent. If the growth is weakly density dependent, by continuity with the case of no density dependent growth, the obtained results are still valid at fixed rotation period T . If this is not the case, we cannot obtain analytical results for the solutions, then simulations are required.

The function of individual growth is given by : G(f, n, w) = w(0.04 -0.01w -10 -9 w 2 n f ) [START_REF] Heaps | Density dependent growth and the culling of farmed fish[END_REF]. The structure of the growth function is generic and can be used for other species. The price is assumed to depend on the weight : p(w) = p 0 w -c 0 .

Instead of estimating the feeding function f (.) as in [START_REF] Heaps | Density dependent growth and the culling of farmed fish[END_REF], to simplify the optimization problem, we decide to search the function f (.) in a parametrized family : f (t) = aw(t) b with a and b unknown coefficients. The determination of the rotation period T is important because of its impact on optimization. To better describe the optimization in the presence of random risk, it is wiser to look at the effective cutting age T and the effective final fish-weight S. Thus we calculate the respective expectations and variances :

E(T ) = T 0 tdF (t) + T (1 -F (T )) = F (T ) λ V ar(T ) = T 0 (t - F (T ) λ ) 2 dF (t) + (T - F (T ) λ ) 2 (1 -F (T )) = 2 λ 2 (1 -F (T ))(F (T ) - λT ) + F 2 (T ) λ 2 E(W) = T 0 w(t)dF (t) + w(T )(1 -F (T )) and V ar(W) = T 0 w 2 (t)dF (t) + w 2 (T )(1 - F (T )
) can be derived from the simulations.

Results and Discussion

The unit of time for the rotation period is the week. We suppose : m = 0.0042 week -1 , λ = 0.005 week -1 , δ = 0.001 week -1 , h = 0.06 week -1 . The results are included in Table 1, to complete, the parameter of optimal feeding function are a = .5748, b = 1.1907 for the unrisky case and a = .5739, b = 1.1698 in presence of risk. The standard deviation of the effective rotation period was calculated.

Risk

We assume that the expected proportion of safe fish after an epidemic event is equal to .5. Without risk and with the presence of risk, there is culling for the optimal solution (Table 1).

The second line of table 1 corresponds to an unrisky case with δ replaced by δ + λ, the result of the line must compared to the last line. Usually the risky case is assimilated to the unrisky case with δ replaced by δ + λ and we can see that the results are significantly different.

The presence of risk involves earlier culling. The earlier culling provides a kind of selfinsurance against risk.

By observing the curves of the Faustmann value W 0 depending on the rotation problem T with optimal culling, we find that the Faustmann value least varies in the vicinity of the optimal rotation period with risk than without risk. This is another consequence of the fact that, with risk the optimal rotation period T is achieved with a relatively low probability.

Conclusion

We have studied the management of an aquacultural system in the presence of risk of epidemic event. In order to determine the optimal culling relative to the Faustmann criterion, we have considered a model of population dynamics, the choosen model is of average fish type. This model has allowed us to make the comparison without and with risk and highlighted the influence of the presence of risk of epidemic event on optimal culling. Specifically, the obtained Faustmann values, without or with the risk of epidemic event, highlighted differences in the criteria to be maximized. In the case of no density dependent individual growth, we have highlighted the impact of the presence of risk on the strategies, generically regardless of the considered species.

In the case of density dependent growth, the calculations for an aquacultural system have shown that the presence of risk of destruction event involves earlier culling for the optimal strategy.

The obtained results are conditioned by the choice of an individual fish growth model and by the specification of a weight model and a price model of fishes. Other studies using models adapted for other species would make the obtained results more generic.

Table 1 :

 1 No * h(t) = h, 85.5 ≤ t ≥ 98.3 110.8(85.1) Yes h(t) = h, 88.6 ≤ t ≥ 101.4 115.2 (87.6) 12.1n 0 Optimal culling for α = 0.5, n(0) = 1500000 fish.

		h(.)	T	W 0
	No	h(t) = h, 91.9 ≤ t ≥ 104.5 117.6	16.4n 0


OP33

The role of cord blood dendritic cells in preventing the differentiation of naive T-helper cells towards Th1 cells Allogeneic cord blood (CB) transplantation is associated with a less severe graft-versus-host disease (GVHD). In this investigation we hypothesised that cord blood dendritic cells not only differ in functional maturity and distribution of DC subsets but also differ with regard to their preference in promoting Th1 and Th2 immune responses. DCs were isolated from cord and peripheral blood mononuclear cells to study differences in DC-expressed costimulatory molecules, the proportion of myeloid and lymphoid DCs, immunstimulatory characteristics and their influence on promoting the differentiation of naı ¨ve T-helper cells towards Th1 and Th2 cells. The results showed that CBDCs were poor stimulators of the mixed leuckocyte reaction compared to PBDCs. CBDCs displayed decreased expression of HLA-DR and CD86. The ratio of lymphoid CD11c-, CD123+ to CD11c+, CD123-myeloid DCs were significantly higher in CB compared to peripheral blood. CBDCs revealed a profound impairment in induction of IFN-G while increasing the induction of IL-4 as compared to adult PBDCs. This result suggested CBDCs preferential priming of naı ¨ve T cells towards Th2 cell.

OP34

Effect of extra-cellular matrix components on adhesion and functional properties of dendritic cells

S. Garcia-Nieto, K. Shakesheff, F. Shakib & A. Ghaemmaghami Lab 3, Immunology Department, A Floor, West Block, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom
The aim of this project was to analyse the effect of different ECM components on the adhesive and spreading ability of dendritic cells (DC) and the possible consequences of those effects on DC functional abilities. Results: Fibronectin and laminin were chosen for the assays because of their abundance and specific location in the LN. Then, we determined optimal concentrations to be used for both proteins. After 24 h of culture, fibronectin provoked an important increase in the number of adhered of DC. Fibronectin produced a dosedependent increase in the occupied perimeter covered by DC. Likewise, fibronectin provoked an evident effect over the spreading ability of DC. ECM components caused an important effect over the functional properties of DC. Conclusions: ECM components have an important effect on the adhesion and spreading ability of DC. Future work will involve analysis of the effect of ECM components over other functional properties of DC and establishing a 3D co-culture of DC and T cells to investigate an immunological interaction with key importance. To aid our understanding of dendritic cell (DC) function, specifically how they guide Th2-type immunity, we have used a gel-based proteomic approach to identify the signature proteins which characterise the function of pro-Th2 DCs (matured with 0-3hRP, released by infective Schistosoma mansoni cercariae within the first 3 h after transformation) versus pro-Th1 DCs (matured with lipopolysaccharide, LPS) and versus immature DCs (iDCs). Software analysis of the 2D-gel electrophoresis showed many similarities in the pattern of spots between the three groups of DCs but also marked changes. In 0-3hRP-DCs versus iDCs, 34 spots were upregulated and 57 downregulated by at least 2-fold. Spots of interest were identified following trypsin digestion and tandem mass spectrometry analysis. Major and/or significant differences were mainly observed on cytoskeletal protein expression (actin, vimentin and moesin) but also on S100 A9, superoxide dismutase 1 and cathepsin B expression. Many changes occurred at the post-translational level. Finally, we showed that 0-3hRP-DCs were less activated/matured than LPS-DCs, supporting the view that Th2 differentiation results from a limited maturation of DCs, but limited divergence is not ruled out. Dendritic cells (DC) are sensitive to their local environment and are affected by proximal cell death. Our aim is to investigate the effect of cell death on DC function. Monocyte-derived DC cultured in the presence of apoptotic or necrotic cell lines were analysed for receptor expression, cytokine production and DC-induced T cell responses. DC exposed to LPS and necrotic, but not apoptotic death (CD95), induced DC maturation. Co-culture with apoptotic death, however caused significant suppression of LPS-and necrotic-induced CD80 and CD86 expression and LPS-induced CD4 + T cell proliferation. An array of cytokines were studied and IFN-c was found to be specifically present with apoptotic co-culture. IFN-c inducible indoleamine 2,3-dioxygenase (IDO), is known to suppress T cell proliferation. We confirmed, through intracellular staining, that both IFN-c and IDO are expressed by DC exposed to apoptotic death and blockade of IFN-c or IDO resulted in a partial release in apoptotic cell suppression of LPS-induced CD4 + T cell proliferation. These results strongly implicate IFN-c

OP35

OP36

Mechanisms of apoptosis-induced dendritic cell suppression

  A. A. Pourfathollah,* N. Naderi,* S. M. Moazzeni & K. Alimoghaddam à *Al-Ahmad Exp. Way. Tarbiat Modares University, School of Medical Sciences, Immunology Department, Tehran, 14155-111, Iran, Al-Ahmad Exp. Way. Tarbiat Modares University, School of Medical Sciences, Immunology Department, Tehran, 14155-111, Iran, à Hematology, Oncology and Bone Morrow Transplantation Research Center, Terhan University of Medical Sciences, Tehran, 14155, Iran

  Proteomic study of differentially matured dendritic cells S. Ferret-Bernard, R. S. Curwen & A. P. Mountford Department of Biology -Area 5-, University of York, PO Box 373, York YO10 5YW, United Kingdom

  C. A. Williams, R. A. Harry & J. D. McLeod Centre for Research in Biomedicine, Faculty of Applied Sciences, University of the West of England, Coldharbour Lane, Bristol BS16 1QY, United Kingdom


Yvan Royon

Pierre Parrend

Stéphane Frénot

Serafeim Papastefanos
email: serafeim@telecom.ntua.gr

Humberto Abdelnur
email: humberto.abdelnur@loria.fr

Dirk Van De
email: dirk.vandepoel@thomson.net

Poel Thomson

Multi-service, Multi-protocol Management for Residential Gateways

When providing services to home users, management is a key activity. In-home devices, and especially the Residential Gateway, can use multiple management technologies for multiple management activities: read/write parameters, but also deploy, update, start and stop software components.

This paper defines management realms around the Residential Gateway, where different actors perform different management activities, using different technologies. We propose techniques that integrate these technologies (TR-069, UPnP, NetConf and JMX). We also address transient issues related to security.

Introduction

Service provisioning to the home is evolving, both on business and technical concerns. The growth is twodimensional: first, new services emerge both inside and outside the home. Second, these services can be provided by new business players. In this context, the Residential Gateway (RG) holds a crucial role. It interconnects the LAN and the WAN worlds; it is the single equipment that links multiple service providers to home services.

In the context of MUSE project we studied the RG in a multi-provider context. This specific context brings new challenges we addressed and we focused on two levels of management for the RG: access management and service management.

The remainder of this paper presents the management challenges in a multi-provider environment; then we present results in two areas: the access management to the RG and an architecture to enable high service management.

Management challenges in a multi-provider environment

In the multi-play model [START_REF] De | The multi-play service enabled Residential Gateway[END_REF], three management realms can be identified, defining who manages what around Residential Gateways. They identify the actors, the management activities, and the technologies involved. These realms are shown in figure 1.

-In the Access realm, the gateway operator manages access-related parameters on the Residential Gateway.

-In the Service realm, various service providers deploy, manage and operate services on the Residential Gateway or on in-home devices.

-In the User realm, home users set preferences on their in-home devices or on the Residential Gateway.

In this multi-management for multi-provider context we focused on three challenges. How can we cope with management protocol diversity, which service model can we use, and how can we handle security issues.

Managing entities in a multi-* world leads to a proliferation of management protocols. This diversity in management technologies brings integration issues. For instance, local management protocols such as UPnP are secluded within the home network; if a manager on the WAN side needs to access a UPnP device, he needs to translate directives between UPnP and the manager's protocol of choice.

RG should host various services managed by various service providers. Those services are piece of applications that are triggered on a pay-per use schema. We studied a global architecture based on OSGi to manage those services. In this OSGi service provisionning environment we focused on the related security issues.

The next section details the studies we made about RG access management an service management architecture.

RG Management proposal

Access Management

The remote management of RG devices is based on the TR-069 document [START_REF]TR-069: WPE WAN Management Protocol[END_REF] published by the DSL forum. This specification presents CWMP (CPE WAN Management Protocol), which is used for the remote management of the RG and other home devices by a device called Auto Configuration Server (ACS), and the version 1.0 of the MIB -Management Information Base for the RG. The MIB is a collection of parameters that can be remotely managed by the ACS. This MIB is further elaborated in the TR-098 [START_REF]TR-098[END_REF] document of the DSL Forum, which presents the version 1.1 of the RG MIB. Also, in the TR-106 [START_REF]TR-106: DSLHome Data Model Template for TR-069-Enabled Devices[END_REF] document the DSL Forum presents a template Illustration 1: Management Realms for the MIMs of home devices. All home devices that support TR-069 should also be TR-106 compliant. A last issue concerns the mono-provider design of the TR-069 protocol: each device can be managed by only one ACS.

-Integrating TR-069 with UPnP Many in-home equipments do not support TR-069 but instead use UPnP technology [START_REF]UPnP Forum, standards and specifications[END_REF]. Because the proximity of UPnP is within the home network, these devices cannot be managed remotely with the current infrastructure. Example applications include the UPnP/AV protocol, which enables media servers (video and audio) to provide streams to media renderers (TV screens or computers). Many devices declare their behaviors through UPnP messages. We designed a UPnP Proxy for TR-069; it is a component that acts as an intermediate between the TR-069 and UPnP protocols and enables the ACS to discover, control and receive events from the UPnP devices even if the ACS is not in the local network of these devices. It is described in the MUSE public deliverable B3.4 [START_REF]Public deliverable DB3.4[END_REF]. The Proxy component is located in the home network and has a connection with the ACS.

An implementation of the Proxy as a software component in the Java programming language is available within the MUSE project. The requirement of this component is that the hosting device has a Java Runtime Environment installed. The general architecture of the Proxy can be seen in the following figure: -Integrating TR-069 with NetConf TR-069 is not the only management protocol currently available. Another candidate is the NetConf [7] proposal from IETF. We propose a extension to NetConf that enables TR-069 RG management from a NetConf agent. This agent acts as a TR-069 proxy for the remote RG as shown in figure 3.

Illustration 3: Interaction with a TR69 based CPE through Netconf

-TR-069 extensions to multi-provider management Finally some extensions to the TR-069 protocol have been made to cope with multi-provider environments. The first improvement deals with auto-provisioning the RG without a predetermined ACS. The ACS is discovered during the first boot of the device, and depending on subscription it is redirected to a specific ACS.

The second extension deals with PING diagnostics.

The managing ACS can trigger a PING procedure handled by the RG. Since the RG can be managed by multiple service provider, the connection can be tangled and the PING procedure is useful to obtain some status.

The last extension to the TR-069 protocol enables TR-069 LAN devices. The use case is based on TR-111 [8] which considers two use cases: a direct connection from ACS to in-home equipments and the use of a NAT translation connection.

All these improvements over the TR-069 RG model enable a better access management of multi-provider environments. In the next section we assume that the connection is functional and we propose an architecture to manage high-level services in a multi-service provider context.

Service Management

OSGi is an emerging standard to manage high-level Java services for in-home environments. We designed an endto-end architecture to handle a multi-provider and multiservices OSGi. The architecture provides lightweight isolation, JMX-based management and security extensions, and is demonstrated with a mock-up developed for the MUSE project.

OSGi-based Residential Gateways

OSGi [9] is the best contender to become the standard execution environment for Residential Gateways. Forums such as HGI base their requirements on the OSGi specifications. The basic idea is that software, packaged as deployment units called bundles, can be dynamically deployed on Residential Gateways running an OSGi framework. Bundles can be downloaded, installed, started, stopped and removed without rebooting the RG. This allows to update the firewall, device drivers, or any software part with close to zero downtime. We have extended OSGi in three domains: multi-provider, remote management through JMX [START_REF] Parrend | Supporting the Secure Deployment of OSGi Bundles[END_REF] and secure deployment of bundles.

Multi-provider OSGi Gateway

Each service provider runs a "virtual gateway" that runs the services he provides. All virtual gateways are handled by a "core gateway" that is handled by some access manager. The core gateway hosts common services and provides an access control to virtual gateways. More details on virtual and core gateways can be found in [11]. This virtualisation enables a co-location of services within the same gateway. Each service set is associated to a specific provider. In order to enable remote management of services, we provide a JMX management framework to OSGi.

Managing Virtual and Core OSGi gateways

MOSGi (for Managed OSGi) has been elaborated during MUSE phase 1, and is currently available in the Apache Felix [12] project. MOSGi runs a JMX management agent within the RG. This agent enables the remote management of Java applications. The MOSGi project also contains a dynamic management console whose presentation automatically adapts to the managed entity. This means that the management console is dynamically built at run-time depending on the deployed services.

In the multi-provider environment each service provider can upload new services (as OSGi bundles).

Security becomes an issue when potential competitors access and configure the same equipment. This lead to some security issues that need to be handled by the OSGi framework.

A Secure OSGi Gateway

The first problem that comes to mind is that download and installation must be verified. We need to identify the sender (the service provider who wants to deploy the OSGi bundle). We also need to check the integrity of the bundle, to ensure it has not been corrupted. This is achieved in three phases.

First, when the Residential Gateway boots, it loads a keystore, which contains public cryptographic keys for service providers. Each system bundle is then verified using this keystore: core system, bundles for remote management, etc. At this point, the OSGi platform is in a usable and verified state.

The second phase is when a service provider creates a bundle. The contents of the bundle is signed, using a jarsigner application. The bundle is then put in a repository.

The third phase is bundle deployment. When a Residential Gateway downloads a bundle from a repository, it validates the integrity of its contents against its hash checksum. If the verification fails, the bundle is rejected. We must alter the OSGi specifications so that life cycle management integrates validation, as is shown in figure 4.

Secure OSGi deployment is covered in details in [13].

Access management and service management activities have been integrated in a demonstration mockup which shows asecure, end-to-end management of multi-service multi-provider environment. The provided use-case relies on two service providers. A fridge service provider proposes a fridge monitoring application, while the UPnP/AV proposes a video provisioning service. We show that both service providers host their services on isolated OSGi virtual gateways. They access in-home equipments (fridge and UPnP media server and renderer devices) through JMX management. Every device is a UPnP device that declares its presence to the RG. Each device has a local user interface that is dynamically uploaded on the iPaq. These local interfaces enable the local user to manage his equipments.

All service-related elements (1, 3, 2, 6) run under Gentoo Linux with the Felix OSGi implementation. We also show heterogeneous systems running the same middleware stack (OSGi/Felix/JMX management): it runs on top of i386/Gentoo Linux (management station), ARM/Gentoo Linux (NLSU2/Linksys), ARM/Debian Linux (iPaq), Via Nehemiah (1000Mhz)/ home-made Linux (service gateway).

Conclusion

The multi-service, multi-provider tendency leads to new kind of problems. During the MUSE project we focused on the impact this paradigm has on the Residential Gateway. We study these impacts at two levels: access management and service management. Access management is a short time issue that already impacts IP connection providers. The service management is a more long-term view of what the user may want in a near future. The permanent connection the xDSL world brings to our homes opens new possibilities for services, and the RG must be able to support it. Management-related proposals presented here do work on hardware that can be found today. However, if we want to run several high-level OSGi services, RG with at least 64 MB of memory are recommended. Alternatively, using gaming consoles or high-end TV set-top boxes instead could be investigated.

Illustration 2 :

 2 Configuration of UpnP-enabled CPE via CWMP/UPnP bridge

  Figure 5 shows the general management environment trial. It shows the various elements we provide in the mock-up. The Access Gateway (5) hosts the TR-069 enabled equipment, the Service Gateway (3) hosts the OSGi extended framework. The service provider environment (1) holds the remote management interfaces. The iPaq (2) holds a local management interface (user realm) and (6) represents various UPnP devices.

Illustration 4 :

 4 Bundle life cycle with REJECTED stateIllustration 5: end-to-end mock-up

Acknowledgments

This research is performed within the MUSE project that is partially funded by the European Commission as part of the European 6th Framework programme.


USE OF AMOXICILLIN IN EXTENDERS FOR

Penicillin (Pen) and Gentamicin (Gent) are recommended and has been largely used in stallion semen extenders in France. Pen is now reserved for human hospitals in France. So the aim of these studies was to validate the replacement of Pen by another betalactam. Amoxicillin (Amox) presents a wider antimicrobial spectrum and is largely marketted in veterinary and human medicine.

Different experiments/trials were performed to evaluate Amoxicillin :

1) its safety for stallion spermatozoa after storage by measuring their motility by a computer-assisted sperm analyzer (2 experiments with fresh semen and 2 experiments with frozen semen).

2) its antimicrobial activity on stallion semen flora by counting the number of aerobic and facultative aero-anaerobic bacteria (number of colony-forming unit (CFU)) (technique OIE, 1988).

3) its global effect on semen stored < 12 h by estimating the fertility per cycle of stallions.

Stallion spermatozoa were diluted either in UHT milk (20.10 6 spermatozoa /ml) and stored at 4°C or in 2) The log of CFU was lower for fresh stored semen diluted in extender containing Gent+Amox (80 mg/L) (3,35) than Gent (3,93), Gent+Pen (3,56) being intermediate, all of these were lower than the control with no antibiotics (4,7) (8 stallions (from 4 studs) x 1 ejaculate x 24 h storage) P<0.05.

3) Fertility per cycle was similar for 5 draught stallions whose semen was diluted, stored at 4°C for 2-8 h, with Gent+Pen (64%, n= 243 cycles, in 2004) and with Gent+Amox (100 mg/L) (69%, n= 288, in 2005), it was the same for 2 light stallions (59% (n=80) and 54% (n=61)).

These experiments has proven the safety of Amoxicillin for the equine spermatozoa, even at high dosage. Its antimicrobial action has been demonstrated: Amoxicillin is almost as efficient as Penicillin for the control of normal flora of stallion semen. This is consistent with previous data [1]. So this antibiotic could be used instead of Penicillin for this indication. In that case, the recommended dose for Amoxicillin in extender for equine spermatozoa is 100 mg/L.

However, in case of pathogens portage or genital infection of the stallion, use of semen for artificial insemination (AI) must be reconsidered. AI can be used if the bacterial infection could be controlled by antibiotics (the ones tested here or others). In that case, the antibiotics must be used at an appropriate dosage that remain compatible with the safety of the spermatozoa [2].

[1] Clement F, Vidament M, Guerin B (1995). Microbial contamination of stallion semen. In : Equine

  STALLION SPERMATOZOA DOLIGEZ P.(1), THIERTANT G.(2), YVON J.M.(3), GERBOIN J.(2), BOTHAMY B.(2), MILLIER C. (2), DE LARTIGUE C.(2), JELODIN A.(3), FERRY B.(2), VIDAMENT M.(3) (1) Les Haras Nationaux, Direction des Connaissances, ARNAC-POMPADOUR, FRANCE ; (2) Les Haras Nationaux, Direction des Services et des Sites, LES BRÉVIAIRES, FRANCE ; (3) INRA, CNRS, Les Haras Nationaux, Univ. Tours, PRC, NOUZILLY, FRANCE Antibiotics in extenders are necessary to control the normal flora present in the stallion semen [1, 2].

  freezing extender (INRA82 + 2% egg yolk + 2.5% glycerol), after centrifugation, and frozen. In these extenders, Gent (Gentalline 80 or 160, Scheringh-Plough ND) was used at 50 mg/L, Pen (10 6 IU, Diamant or Panpharma or Sigma ND) was used at 50 000 IU/L if non specified. Amox used were Clamoxyl 500 mg (ND, Beecham) in experiment 1a, and Clamoxyl 1g IM (ND, Glaxo-Smith-Kline) diluted in apyrogenic water in all other experiments and trials.Results 1) Within experiment, the motility was similar : a -after storage for 48 h in milk containing no antibiotics, Pen+Gent, Pen (40, 400 or 5100 IU/mL) or Amox (20, 200 or 1000 mg/L) (3 stallions x 2 ejaculates) b -after storage for 72 h in milk containing no antibiotics, Pen+Gent, Pen (50 or 500 IU/mL) or Amox (25 or 250 mg/L) (5 stallions x 1 ejaculate) c -after freezing and thawing in freezing extender containing Gent+Pen or Gent+Amox (400 mg/L) (6 stallions x 2 ejaculates) d -after freezing and thawing in freezing extender containing Gent+Pen or Gent+Amox (100 mg/L) (122 stallions, > 877 ejaculates/group): 49% vs 50%, respectively.

  Reproduction VI. Biology of Reproduction, Monograph Series I. Sharp D.C., Bazer F.W. Eds. Society for the Study of Reproduction Publ., Madison, USA, 779-786. [2] Varner DD, Scanlan CM, Thompson JA, Brumbaugh GW, Blanchard TL, Carlton CM, Johnson L (1998). Bacteriology of preserved stallion semen and antibiotics in semen extenders. Theriogenology, 4, 559-73.


Pierre Parrend
email: pierre.parrend@insa-lyon.fr

Samuel Galice
email: samuel.galice@insa-lyon.fr

Stephane Frenot
email: stephane.frenot@insa-lyon.fr

Stephane Ubeda
email: stephane.ubeda@insa-lyon.fr

Identity-Based Cryptosystems for Enhanced Deployment of OSGi Bundles

The OSGi platform is designed to make Java software extensible at runtime. This undeniably presents a great interest in several domains like embedded platforms or enterprise application servers. However, securing the deployment of the OSGi components, or bundles, proves to be a major challenge. The current approach consists in digitally signing the bundles and certifying the signature through a Public Key Infrastructure.

We propose to replace this technology with Identitybased cryptographic mechanisms, which provide both better performances and simplified key management. We present an infrastructure for initialization and use of Identity-based key management, and define the digital signature of bundles using such a cryptographic scheme. Based on our implementation, we provide a comparison between PKI management and Identitybased Key Management. The proposed approach proves to support radical improvement in the key management process, especially in strongly asymmetric system such as OSGi-based Home Gateway, where a few providers publish services for millions of potential users.

Introduction

Nowadays, the ever-growing connection to Internet of homes and enterprises -often through a connection over ADSL Wide-band Access -brings new capabilities for home entertainments or professional services. The Home Gateway which classically provides the connection to Internet becomes a central device that supports execution of high-level services. These services need to be dynamically loaded on the gateway at runtime, which is supported by the OSGi Platform. The OSGi environment is a lightweight overlay to a Java Virtual Machine. This runtime extension enables new code to be executed on the Home Gateway, and must therefore be strongly protected. This protection is currently performed through the digital signature of the bundles with DSA algorithms, which imply a complex key management. We propose to replace DSA signature with digital signatures that use Identity-based Cryptography. This recent cryptographic scheme enables in particular to dramatically simplify the management of public key, by replacing Public Key Certificates with a string identifier of the signer. A parameter which is specific to the Certification Authority enables every client to deduce to public key from the identifier, and thus to check whether the Certification Authority, called Private Key Generator (PKG) has used a valid private key for the bundle signer.

We present in this paper other works related to secure OSGi and dynamic systems in Section 1, and the principle of Identity-Based Cryptography, in Section 2. The infrastructure for secure deployment of OSGi bundles is presented in the section 3. We then provide a validation of the proposed approach in Section 4, and conclude the paper.

Related Works

The security of the component deployment process is enforced is most cases through context-dependent solutions. We provide here an overview of the principal existing solutions.

The default Bundle Signature mechanisms of deployment of OSGi bundles is based on the Java Archive signature [START_REF]Inc. Jar file specification[END_REF]. It is strengthened by the OSGi Core Specification Release 4 [START_REF]Osgi service platform, core specification release 4[END_REF] to provide a higher level of security in the deployment process. In particular, OSGi bundles can not be extended with new resources, when Java Archives can [START_REF] Parrend | Supporting the secure deployment of osgi bundles[END_REF]. You can find further technical information related to digital signature of OSGi bundles in [START_REF] Parrend | Secure component deployment in the osgi(tm) release 4 platform[END_REF].

Several alternatives to the OSGi platform have been proposed to support this secure deployment. The Cingal Model [START_REF] Dearle | A flexible and secure deployment framework for distributed applications[END_REF] manages the deployment of components through insertion of metadata in the components. The bundles are wired together. Each bundle carries authentication metadata, which comprises the digital signature and the identity of the signer. The implementation is not compatible with the OSGi framework, but the principles are very similar. Another alternative is Preatoria [START_REF] Gaedke | Supporting secure deployment of portal components[END_REF] which is a framework dedicated to the deployment of Web Services. The security mechanisms are based on the Web-Service standards, which enables to support both deployment and execution time security. Praetoria is developed on the .Net platform. Since it uses Web Service technology, it is less flexible than the OSGi platform. In the context of enterprise systems, the SmartFrog (Smart Framework for Object Groups) [START_REF] Low | A smartfrog tutorial[END_REF] has been developed. The security is performed through the encryption of all communications and data transfer. This approach is straightforward in environments where all entities are known, but can not be easily mapped toward large-scale or evolutive systems.

Some solutions are specifically target at the OSGi framework. For instance, Kim et al. propose to rely on Message Authentication Code (MAC) based authentication. Consequently, the asymmetric cryptographybased signature with SHA-1 and DSA algorithms is replaced by symmetric cryptography. The creation of a shared secret at bootstrap time is required [START_REF] Kim | A mac-based service bundle authentication mechanism in the osgi service platform[END_REF]. This process is more lightweight that the one specified by the OSGi Alliance. However, the use of symmetric cryptography makes the key management more complex and less robust: since the secret key is shared, the non-repudiation of actions can not be guaranteed, keys can be divulgated to third parties, and key revocation is extremely difficult to support. Moreover, the actual benefit is not quantified, which would be of a great interest when choosing to give up the current standard. This work is extended by Lim et al. to take advantage of XML technology signature, that supports MAC based authentication [START_REF] Lim | Bundle authentication and authorization using xml security in the osgi service platform[END_REF]. Since XML is usually not considered as a lightweight technology, this extension seems paradoxical with the use of limited resource devices. Again, the lack of quantification of the relative performances of the various solutions does not provide sufficient data to choose between the various solutions.

Identity-based Cryptography has not yet been applied to the deployment of OSGi bundles -or other kind of components. However, several propositions have been made to exploit their possibilities in the context of distributed and pervasive systems. In the context of Health-Care systems -which are a potential applications for Home Gateways -Mont propose to use IB Cryptography to support a secure messaging service [START_REF] Mont | A flexible role-based secure messaging service: Exploiting ibe technology in a health care trial[END_REF]. The authors take advantage of the increased flexibility brought by IB Cryptography to enforce rolebased security mechanisms. The technology has also been used in the context of the Grid to provide secure communication channels [START_REF] Stading | Secure communication in a distributed system using identity based encryption[END_REF].

Identity-Based Cryptosystems

Until recently, encryption techniques have relied on long, randomly generated keys that must be mapped to identities using digitally-signed documents, called certificates. The management of these certificates, and the need to fetch a certificate before encrypting to a person or machine, has made encryption very difficult.

Identity-Based Encryption (IBE) takes a completely new approach to the problem of encryption: IBE is a key authentication system in which the public key of a user is some unique information about the identity of the user . That allows any party to generate a public key from a known identity value such as an ASCII string (e.g. a user's email address) enabling data to be protected without the need for certificates. A trusted third party, called the Private Key Generator (PKG), generates the corresponding private keys. Each new user associated to the trusted domain must requests his private key from this PKG. The master key is kept secret by the PKG and there is no authority in charge of the generation of this master key. The PKG controls the mapping of identities to decryption keys in order to ensure the protection of the system.

Historically, the design of a functional Identity-Based Cryptosystem (IBC) was a long-standing open problem in cryptography. The notion of IBC was first introduced by A. Shamir [START_REF] Shamir | Identity-based cryptosystems and signature schemes[END_REF] in 1984. In 2001, D. Boneh and M. Franklin [START_REF] Boneh | Identity-based encryption from the weil pairing[END_REF] were the first to propose a fully adapted model with the help of elliptic curves and the Weil and Tate bilinear pairings serving as building blocks for these Public Key Cryptosystems (PKC).

As a result, parties may encrypt messages (or verify signatures) with no prior distribution of keys between individual participants. This is extremely useful in cases where pre-distribution of authenticated keys is inconvenient or infeasible due to technical restraints. However, to decrypt or sign messages, the authorized user must obtain the appropriate private key from the PKG. A caveat of this approach is that the PKG must be highly trusted, as it is capable of generating any user's private key and may therefore decrypt (or sign) messages without authorization. Because any user's private key can be generated through the use of the third party's secret, this system has inherent key escrow.

The power of IBE is in its simplicity. By using well-known identifiers, such as email addresses, as public keys, IBE enables security policies to be encoded directly into encryption and authentication methods, eliminating the need for cumbersome certificates and Certification Authorities. By eliminating the need for certificates, IBE removes the hurdles of PKI: certificate lookup, life-cycle management, Certificate Revocation Lists, and cross-certification issues. IBE's simplicity also enables it to be used in ways PKI could not: IBE can be used to build security systems that are more dynamic, lightweight and scalable. The IBC based on elliptic curves have numerous advantages as the gain in size of the keys and the reduced computational time. Moreover, they provide as well signature/verification processes as encryption/decryption operations within correct times and for a lower cost of CPU or memory usage than in the case of classical cryptography (as DSA).

We propose thus to utilize IBC to deploy bundle in the OSGi context with a high level of security in parallel. We claim that the resulting protocol is more lightweight in both cost of management and network communications than usual PKC based on traditional cryptographic tools (RSA, DSA). To prevent the natural key escrow problem presents in the native IBE system since the PKG knows each private key, we decide to use the Chang-Zeng-Kim signature scheme which provides a solution to this issue. To support our proposition, we intend to implement a fully functional version of our protocol. The performance of our protocol is comparable to the performance of ElGamal signature scheme. The security of the system is based on a natural analog Extract, Sign and Verify. Considering Alice a signer with her identity d, she signs a message in the Sign phase by using the private key given by the PKG. In the Verify phase, Bob verifies the validity of her signature in an IBS scheme just by using her identity ID A and the params made publicly available by the PKG.

The Chen-Zhang-Kim's Identity-based Signature (CZK-IBS) scheme (see [START_REF] Chen | A new ID-based group signature scheme from bilinear pairings[END_REF] for more details about this scheme) is used in the signing and verification phases in order to eliminate the inherent Key Escrow problem as cited in Introduction. This choice is highly motivated by some non-repudiation considerations especially in the context an multi-provider and open environment as the OSGi platform. Another motivation for this scheme is to help the public bundle deployment. Rather than storing a big database of public keys the

The OSGi Security Architecture with CZK-IBS

The substitution of the classical Public Key Infrastructure (PKI) with an Identity-based key management infrastructure for securing the deployment of OSGi bundles has two main advantages. First, the process of key management is greatly simplified, which makes the actual use of secure deployment more realistic than with a PKI [START_REF] Ellison | Ten risks of pki: What you're not being told about public key infrastructure[END_REF]. Secondly, the specifications of this new deployment scheme provides a support to extend the original functionalities with the confidentiality of the bundles. Three phases need to be specified for the deployment of CZK-IBS signed bundles: the initialization of the cryptographic objects, the process of bundle deployment, and the mechanisms of bundle signature.

Initialization

Initialization of the cryptographic objects in our infrastructure is shown in the figure 1. The process is the following.

First, all entities that need to be identified must be initialized. The parameters of the trusted PKG which performs the management of cryptographic objects in our infrastructure must be distributed through a secure channel to all participants, along with their own unique identifier. This is typically done offline. In the context of telecommunication services such as those developed in the Muse Project, the PKG is located on the Access Control Server. The identifier delivered to the participants of the system contains the following information: a unique string identifier. The PKG stores a copy of the public identities to be able to identify valid participants. This offline initialization of cryptographic objects is typically done through a USB key or a smart card where the specified informations are stored. This pre-identification step is mandatory in closed systems, such as Home Services, monitoring systems, or enterprise informations systems. It can be by-passed in open systems such as the deployment of open source software or in ambient systems, where all actors that want to take advantage of the infrastructure should be allowed to. While allowing unknown entities to be identified, such an approach guarantees the uniqueness of the bundle providers, and thus prevents both the tampering of the bundles and the impersonation of the providers.

Secondly, the bundles Issuers retrieve their private key from the PKG. Therefore, the PKG is implicitly granted a strong trust, since it could forge any private key of all entities that rely on it. Nevertheless, the CZK-IBS provides a tracing scheme to detect the PKG's impersonation. The retrieval of the private key must be performed again when the issued private key is expired. Typically the span-life of a private key would be a short period of time, such as a day or a week. This short validity of time of the private key makes the revocation of the issuers a lightweight process, since it is sufficient not to issue a new private key for them.

Thirdly, the client platforms are initialized. A client needs two types of data so as to subsequently check the validity of the bundles it loads. The first type, the socalled 'params' of the PKG must be known. They allow to compute the public key of each bundle issuer from their identity and above all, to verify the signature of the signed bundles. The second type of data is a list of trusted bundle issuers that are considered as valid must also be available. Otherwise, it would be possible for any malicious issuers to sign and publish bundles that would be considered as valid.

Bundle Deployment with CZK-IBS

The process of deployment with CZK-IBS scheme is shown in the Figure 2. It is very similar to the one in the context of a classical PKI, with a notable gain in term of management complexity.

The signature phase is similar to the signature mechanism in the PKI based model. The differences lay in the cryptographic algorithms that are used (see section 3.3) and the frequency of the update of the private key of the signers. The validation phase is done in the same way as in the case of the PKI. The validation process must be adapted to the algorithms. The validation of the public key certificate is replaced by the control of the validity of the identity of the signer: its identity is compared against the list of valid signers that has been obtained during the initialization phase.

The confidentiality is achieved by encrypting the bundles before their publication. Because it is not possible to publish a signed bundle for all clients, groups must be defined that gather the client platforms with similar functional and trust profiles. The clients retrieve the private key of their group through a request to the PKG. Consequently, this latter must maintain a list of the users' identities for each group. The withdrawal of clients from the group is dealt with by a regular key update. Former group members can not have access to the new keys. The total number of groups should be reduced, so as to limit the number of copies of a single bundle that are encrypted with different public keys. Moreover, the user authentication mechanism is also based on its identity.

Bundle Signature with CZK-IBS

The process of signing bundles is pretty similar to the classical one [START_REF] Parrend | Secure component deployment in the osgi(tm) release 4 platform[END_REF]. The algorithms used for obtaining the hash values are the same but those generating the digital signature are different. Into the bargain, the absence of a public key certificate makes the CMS format [START_REF] Housley | Cryptographic message syntax (cms)[END_REF] obsolete. The structure of a signed bundle using CZK-IBS scheme is depicted in the figure 3. Each resource of the archive is identified in the META-INF/MANIFEST.MF file, along with its hash value. So as to allow several signers to sign the bundle, the hash value of this Manifest file is stored in a so-called Signature File, as well as the hash value of the various entries of the Manifest. The digital signature itself is realized on the Signature File, and stored We propose to replace the CMS compliant Signature Block by an IB-CMS compliant block, that is to say a modified CMS file that contains the information related to the signer, such as its identifier, and the properties of its key, such as the period of validity. The signer informations are the following: the signer identifier ('signerID'), the identifier of the PKG that issues the private key ('keyissuerID'), the date of the emission of the key (with the year, the month, the day), the validity period of the key (an integer value, and a time unit, which can be day, week, month or year), and the name of the algorithms that are bound to this key. The encryption algorithm is mandatory. In most case, the hash algorithm is bound to the encryption algorithm, and must be specified. The CZK-IBS scheme is also integrated in the IB-CMS file. Since it is based on Elliptic curve cryptography, it is more performant and more compact that the classical DSA one. Two fields are removed from the original specified format, because they make no sense in the context of IBC: the X.509 public key certificate (or list of certificate, if delegation of signature was provided), and the Certificate Revocation List (CRL). Consequently, the IB-CMS file is more lightweight than the CMS one was, which can be a useful property in environments with limited resources.

The substitution of classical PKI-based asymmetric cryptography by the Identity-based scheme makes it possible to build an infrastructure for secure deployment of bundles that is both easier to manage, and less greedy in term of resource consumption. We claim that these two properties not only bring an improvement to the current specified solution, but also that it merely makes it a realistic choice for systems that are both complex and limited in their resources.

Security Analysis

We present in this section a short security analysis of our infrastructure against some classical attacks. The basic security properties a cryptosystem should provide are Confidentiality, Integrity, Authentication, and Non-repudiation. Confidentiality is keeping information secret from all other than those who are authorized to see it. Integrity is ensuring that the information has not been altered by unauthorized or unknown entities. Authentication is the assurance that the communicating party is the one that it claims to be. Non-repudiation is preventing the denial of previous commitments or actions. The security of each cryptographic primitive used in our proposition was discussed in the referenced paper [START_REF] Chen | A new ID-based group signature scheme from bilinear pairings[END_REF] and was clearly established. Although the first IBC security notions were proposed in [START_REF] Boneh | Identity-based encryption from the weil pairing[END_REF], there is no work yet aiming at establishing the strength of this notion in a full security analysis. So far, only the indistinguishability based security notions, as well as their variations have been considerated in the literature.

Digital Signature is a fundamental cryptographic primitive which provides authentication, integrity and non-repudiation. The unforgeability of the hashed message guarantees the integrity of the CZK-IBS Signature. This property is provided by the collision resistant property of the hash function used. Due to recent results published in [START_REF] Wang | How to break md5 and other hash functions[END_REF], at least SHA-1 must be used to be sure that the hash function does not permit to compromise the bundle signature integrity.

In our proposition, the PKG plays an important role by defining entirely the security domain and thus may potentially forge signature for any message. Nevertheless, the CZK-IBS scheme provides a way to circumscribe this problem. The dishonesty of the PKG can be proved by the Service Issuer by providing a proof of his secret key (S ID A , r) through a knowledge challenge. So there is Authentication in the system.

The PKG also plays an important role by ensuring that all the valid Service Issuers are trustworthy. Actually, the Service Provider in an OSGi based Service Environment exists outside the home network as does the Home Gateway manager for managing the home gateway and authenticating the users. Our protocol is designed under the assumption that Identitybased Infrastructure is used according to Home Gateways storage and computation capabilities, the params are shared between all entities. Another assumption is that the service users trust the Service Manager. Finally, Home Gateway knows that the PKG is legitimate by using its public key initialized in a preinstallation phase.

Validation

The validation of our approach is performed in two steps. First, we present the technology that we use to develop our prototype. Then we perform an qualitative and quantitative evaluation of the benefits of Identitybased cryptography in the process of secure deployment for OSGi Bundles.

Implementation

A prototype for IB Cryptography systems is currently being built at the CITI Laboratory. It will be integrated with the SFelix suite we previously developed1 , which is an implementation of current OSGi Release 4 specifications of Bundle Signature.

The SFelix suite is written in Java, to be fully compliant with the OSGi environment. However, current implementations of identity-based cryptography libraries, Miracl and Voltage, are only available in C. This does not prevent experimentation, since call to native libraries are well supported in Java, but limits the portability of the solution.

We now discuss the existing IB cryptographic libraries. The first implementation is based on Miracl which is a portable C/C++ library providing a full implementation of Multiprecision Arithmetic. In particular it includes all the primitives necessary to implement Number Theoretic based methods for Public Key Cryptography, such as Diffie-Hellman, RSA and DSS. Complete support is also provided for implementation of Elliptic Curve Cryptosystems over the fields GF(2m) and GF(p). The MIRACL big number library also contains an experimental implementation of IBE2 . The second implementation is based on Voltage IBE Toolkit which is a set of tools that enable developers to quickly and easily incorporate Identity-Based Encryption into their applications. Using the Voltage IBE Toolkit, applications can seamlessly integrate with the Voltage Security platform and take advantage of its centralized administration, advanced policy management, and key distribution architecture3 .

Our IB-based digital signature tools are in their early development stage. However, this does not prevent us to perform a precise evaluation of the proposed framework.

Benefits for Security Management

The prototype we develop allows us to evaluate the actual benefits of Identity-Based Cryptography in the process of deploying OSGi Bundles. This evaluation makes it possible both to confirm that Identity-Based Cryptography hold its promises, and to draw actual pros and cons of classical PKI-based systems and IB-Crypto based systems.

A systematic comparison between Classical PKI and Identity-Based Cryptography PKI is given in Table 1. The first main difference, which is the ground if the simplicity of management of IB-PKI systems, is that the public key must be disseminated as is in the context of classical PKI, and that it is directly deduced from a string identifier and from a Private Key Generator specific parameter with IB-Cryptography. Consequently, keys are updated using huge periods in classical PKI, whereas they can be updated daily with IB-Crypto: if a time stamp is appended to the signer's identifier to generate the public key, this latter can be updated daily. The client only needs to re-generate locally the new public key. The benefit of regular key update is that public key revocation is performed transparently. When a signer is no longer part of the system, she can not retrieve a new daily key pair from the PKG. So she can no longer sign bundles. On the contrary, classical PKI infrastructures imply that the client must be notified when a signer is revoked, and thus complex Public Key Revocation mechanisms must be available. Moreover, Key size and time for signature verification are decreased with IB-Cryptography.

PKI based on RSA or DSA algorithms still have advantages over Identity-based Cryptography. In particular, the speed of signature generation is greater using DSA or RSA algorithms. But the main drawback of Identity-Based Cryptography is that the Private Key Generator must be fully trusted, since he knows the private key of all entities of the systems. Whereas classical PKIs are based on the certification of public keys: they validate this latter without having access to the private key. Thus, the Certification Authority requires a lower trust level than PKGs. We solve this problem by using the IB-CKS cryptographic scheme, which makes key escrow traceable, and therefore forces the PKG to be honest.

A quantitative analysis shows that Digital Signature of Bundles using IB Cryptography provides a great enhancement in key management overhead when compared to PKI infrastructure. When a new key is used by a signer, this latter makes a communication with the PKG to retrieve the new private and public keys. Assume that N signers are authorized to publish bun-dles in the systems, this is tantamount to N communications -a reasonable assessment is than N is of the order of magnitude of 10, or even less. When a client loads a bundle, it can check locally that the key is valid and has been issued by the trusted PKG. So no communication with the PKG is required. The total number of communication with the Certificate Authority is thus N. In the context of PKIs, the signers need to certify their Public Key Certificates, which amounts to N communications. When they load a new bundle, the clients must check that this Public Key has not been revoked. This is done through a request to the Certification Authority, which provides a Certificate Revocation List (CRL). The number of client is noted M, with M of the order of magnitude of a couple of million, if we assume as in the Muse European Project that the Home Gateway is provided with the ADSL modem (in France, the number of client varies between 1 and 5 millions clients for each ADSL providers). On the first hand, the PKG must stand a traffic of some tens of connections daily. On the other hand, the PKI must be available for several millions of users. If the PKI is replicated on the DSLAMs, each replica serves no more than 400 clients, but all DSLAMs must support CRL functionalities, which obviously causes an important system update overhead. Identity-based Key Management systems therefore has a radical technical advantage over PKIs, which could soon be translated in radical financial gains for telecommunications firms.

Since we have developed prototypes for both DSAbased digital signature and Identity-based systems, it would be of interest to compare the relative computation speed of both techniques. However, the Bundle Digital signature we use is written using the Bouncycastle Java library for DSA-signature, and the Identitybased Cryptographic C libraries are accessed from Java code through native calls. Quantitative comparison would be a comparison of C and Java more than an evaluation of both techniques. We intend to perform these evaluation as soon as a Java implementations of Identity-based Cryptographic tools are available.

PKI and IB Cryptography have both pros and cons

what concerns cryptographic and system security properties. But the simplification in the key management process with Identity-based systems, which allows client to check digital signatures without any need to contact a certification authority proves to allows dramatic key management gains, in particular in strongly asymmetric systems such as telecommunication Home Gateways. We have proposed in this paper a protocol to secure the deployment of OSGi bundles by using recent cryptographic algorithms based on elliptic curves and bilinear pairings. Our proposition relied on the CZK-IBS scheme to support the Public Key Infrastructure (PKI) instead of the classical solutions as those specified by the OSGi Alliance. The use of Identity-based cryptography has several advantages: first, the key management overhead is greatly reduced, which can provide a radical advantage in the case of strongly asymmetric systems such as Home Gateway infrastructures, where a couple of providers publish services for an important number of clients. The public keys do not need to be published, since they can be deduced from the identifier of their owner. Moreover, the complex revocation scheme vanishes and is replaced by the frequent update of the keys, typically every day or week. Another advantage of our proposition which has probably a less radical impact is the fact that the keys and signatures used are based on Elliptic-curve cryptography. They are therefore more compact than those bounded with the DSA algorithm which is currently used for signing archives. We have also defined in this paper the process for securing the deployment of OSGi bundles using Identity-based cryptography, as well as the structure of a signed OSGi bundle by the CZK-IBS scheme. Both qualitative and quantitative benefits of the approach were discussed. Yet, our approach has some limitations, in particular the centralization of the security scheme around the PKG, which becomes a single point of failure. Its compromission means a high impact on the overall security of the system.

PKI

However, we believe that Identity-based Cryptography enables to greatly reduce the key management overhead, and thus may succeed in large scale systems where PKI have so far proven to be very difficult to manage.

Figure 1 .

 1 Figure 1. Global view of the initialization of the cryptographic Objects

Figure 2 .

 2 Figure 2. Secure Deployment of OSGi Bundles with CZK-IBS scheme

Figure 3 .

 3 Figure 3. Structure of a signed bundle, using Identity-based Cryptography

Table 1 . Pros and Cons of classical PKI and IB-PKI Approaches

 1

	IB-PKI	Ratio

This work is partially funded by MUSE II IST FP6 Project n026442.

http://sfelix.gforge.inria.fr/

http://www.shamus.ie/

http://developer.voltage.com