Analysis of a key distribution scheme in secure multicasting

This article presents an analysis of the secure key broadcasting scheme proposed by Wu, Ruan, Lai and Tseng [Proceedings of the 25th Annual IEEE Conference on Local Computer Networks (2000), 208-212]. The study of the parameters of the system is based on a connection with a special type of symmetric equations over finite fields. We present two different attacks against the system, whose efficiency depends on the choice of the parameters. In particular, a time-memory tradeoff attack is described, effective when a parameter of the scheme is chosen without care. In such a situation, more than one third of the cases can be broken with a time and space complexity in the range of the square root of the complexity of the best attack suggested by Wu et al. against their system. This leads to a feasible attack in a realistic scenari

Analysis of a key distribution scheme in secure multicasting

This article presents an analysis of the secure key broadcasting scheme proposed by Wu, Ruan, Lai and Tseng [Proceedings of the 25th Annual IEEE Conference on Local Computer Networks (2000), 208-212]. The study of the parameters of the system is based on a connection with a special type of symmetric equations over finite fields. We present two different attacks against the system, whose efficiency depends on the choice of the parameters. In particular, a time-memory tradeoff attack is described, effective when a parameter of the scheme is chosen without care. In such a situation, more than one third of the cases can be broken with a time and space complexity in the range of the square root of the complexity of the best attack suggested by Wu et al. against their system. This leads to a feasible attack in a realistic scenari

Existence of a limiting distribution for the binary GCD algorithm

AbstractIn this article, we prove the existence and uniqueness of a certain distribution function on the unit interval. This distribution appears in Brent's model of the analysis of the binary gcd algorithm. The existence and uniqueness of such a function was conjectured by Richard Brent in his original paper [R.P. Brent, Analysis of the binary Euclidean algorithm, in: J.F. Traub (Ed.), New Directions and Recent Results in Algorithms and Complexity, Academic Press, New York, 1976, pp. 321–355]. Donald Knuth also supposes its existence in [D.E. Knuth, The Art of Computer Programming, vol. 2, Seminumerical Algorithms, third ed., Addison-Wesley, Reading, MA, 1997] where developments of its properties lead to very good estimates in relation to the algorithm. We settle here the question of existence, giving a basis to these results, and study the relationship between this limiting function and the binary Euclidean operator B2, proving rigorously that its derivative is a fixed point of B2

The contribution of patch topology and demographic parameters to population viability analysis predictions: the case of the European tree frog

Population viability analyses (PVA) are increasingly used in metapopulation conservation plans. Two major types of models are commonly used to assess vulnerability and to rank management options: population-based stochastic simulation models (PSM such as RAMAS or VORTEX) and stochastic patch occupancy models (SPOM). While the first set of models relies on explicit intrapatch dynamics and interpatch dispersal to predict population levels in space and time, the latter is based on spatially explicit metapopulation theory where the probability of patch occupation is predicted given the patch area and isolation (patch topology). We applied both approaches to a European tree frog (Hyla arborea) metapopulation in western Switzerland in order to evaluate the concordances of both models and their applications to conservation. Although some quantitative discrepancies appeared in terms of network occupancy and equilibrium population size, the two approaches were largely concordant regarding the ranking of patch values and sensitivities to parameters, which is encouraging given the differences in the underlying paradigms and input dat

Analysis of a key distribution scheme in secure multicasting

This article presents an analysis of the secure key broadcasting scheme proposed by Wu, Ruan, Lai and Tseng. The study of the parameters of the system is based on a connection with a special type of symmetric equations over finite fields. We present two different attacks against the system, whose efficiency depends on the choice of the parameters. In particular, a time-memory tradeoff attack is described, effective when a parameter of the scheme is chosen without care. In such a situation, more than one third of the cases can be broken with a time and space complexity in the range of the square root of the complexity of the best attack suggested by Wu et al. against their system. This leads to a feasible attack in a realistic scenario

Analysis of a key distribution scheme in secure multicasting

This article presents an analysis of the secure key broadcasting scheme proposed by Wu, Ruan, Lai and Tseng [Proceedings of the 25th Annual IEEE Conference on Local Computer Networks (2000), 208-212]. The study of the parameters of the system is based on a connection with a special type of symmetric equations over finite fields. We present two different attacks against the system, whose efficiency depends on the choice of the parameters. In particular, a time-memory tradeoff attack is described, effective when a parameter of the scheme is chosen without care. In such a situation, more than one third of the cases can be broken with a time and space complexity in the range of the square root of the complexity of the best attack suggested by Wu et al. against their system. This leads to a feasible attack in a realistic scenari

Partitions modulo n and circulant matrices

AbstractThis paper is about a connection between a general problem of partitions in Z/nZ and the expression of determinants of certain circulant matrices. The main result of the article is a method for calculating, in certain special cases, explicit formulas for the number of partitions of elements in Z/nZ in distinct summands and the number of partitions of elements in Z/nZ with less than t repetitions. Explicit formulas for partitions in Z/nZ in the general case can be found by explicitly calculating the determinants of certain circulant matrices

DIFFUSION ACOUSTIQUE PAR DES COQUES CYLINDRICO-HEMISPHERIQUES IMMERGEES EN INCIDENCE VARIABLE

L'ETUDE DE LA DIFFUSION ACOUSTIQUE PAR DES CIBLES CYLINDRIQUES LIMITEES PAR DEUX HEMISPHERES EST TRAITEE DANS LES DOMAINES TEMPOREL ET FREQUENTIEL. CETTE ETUDE FOURNIT UNE INTERPRETATION PHYSIQUE COMPLETE DE LA SIGNATURE ACOUSTIQUE PROPRE A CE TYPE D'OBJETS CYLINDRICO-HEMISPHERIQUES EN RETRODIFFUSION. POUR SE FAIRE, UNE DEMARCHE EXPERIMENTALE EST COMPLETEE PAR UNE APPROCHE THEORIQUE. L'EXCITATION ULTRASONORE DE CES OBJETS EST REALISEE POUR TOUTES LES INCIDENCES, DEPUIS L'INCIDENCE AXIALE (SUIVANT L'AXE PRINCIPAL DE L'OBJET) JUSQU'A L'INCIDENCE NORMALE (SUIVANT LA DIRECTION NORMALE A L'AXE PRINCIPAL). LES CIBLES CREUSES IMMERGEES DANS L'EAU SONT EN ACIER INOXYDABLE, DE RAPPORTS DES RAYONS INTERNE SUR EXTERNE EGAUX A 0,99 (PAROI EXTRA-MINCE) ET A 0,97. LES RESULTATS EXPERIMENTAUX OBTENUS SUR TROIS CIBLES EXTRA-MINCES ONT MONTRE DEUX ZONES ANGULAIRES DISTINCTES DE RETRODIFFUSION SE RAPPORTANT A L'EXCITATION DE LA CIBLE CONSIDEREE D'UNE PART SUR SA PARTIE HEMISPHERIQUE ET, D'AUTRE PART, SUR SA PARTIE CYLINDRIQUE. DANS LA REGION ANGULAIRE CORRESPONDANT A L'EXCITATION HEMISPHERIQUE DE L'OBJET UNE MEME REPONSE ACOUSTIQUE PROCHE DE CELLE OBTENUE POUR L'INCIDENCE AXIALE EST OBSERVEE. LES SIGNAUX EXPERIMENTAUX OBTENUS POUR CETTE INCIDENCE AXIALE S'ACCORDENT AVEC CEUX CALCULES PAR UN MODELE NUMERIQUE EMPLOYANT LA METHODE D'ELEMENTS FINIS COUPLEE A LA METHODE D'ELEMENTS DE FRONTIERE. CONCERNANT L'EXCITATION CYLINDRIQUE DE LA CIBLE, UN MODELE GEOMETRIQUE BASE SUR L'ANALYSE DES PARCOURS DES ONDES HELICOIDALES PERMET D'IDENTIFIER LES ECHOS DES REPONSES TEMPORELLES. DES RESONANCES LIEES A LA SECTION CYLINDRIQUE DE L'OBJET ET A SA LIMITATION SONT ALORS MISES EN EVIDENCE. L'INFLUENCE DE SUREPAISSEURS ANNULAIRES INTERNES DE COQUE SUR LA RETRODIFFUSION EST EGALEMENT ETUDIEE DANS LE CAS DE L'EXCITATION AXIALE POUR DES CIBLES PLUS EPAISSES. DES ECHOS SUPPLEMENTAIRES DE REFLEXION SUR CES INHOMOGENEITES APPARAISSENT ET DES DECALAGES EN FREQUENCE DE RESONANCE SONT ALORS INTRODUITS.LE HAVRE-BU Centrale (763512101) / SudocSudocFranceF

Diffusion acoustique par des coques cylindriques limitées immergées

LE HAVRE-BU Centrale (763512101) / SudocSudocFranceF

Influence de raidisseurs internes régulièrement espacés sur la diffusion acoustique par une coque cylindrique finie immergée (diffusion de Bragg et diffusion de Bloch-Floquet)

LE HAVRE-BU Centrale (763512101) / SudocSudocFranceF