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701 résultats
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Séminaire
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Cryptographie
La sécurité des schémas de Feistel aléatoires
Orateur : Jacques Patarin - Université de Versaille
Les schémas de Feistel fournissent une méthode standard pour construire des permutations pseudo-aléatoires, ou encore pour construire des algorithmes de chiffrement par blocs. Depuis le célèbre résultat de Luby et Rackoff sur les schémas de Feistel aléatoires à 3 et 4 tours (1989) les preuves de sécurité et les attaques sur ces schémas ont été améliorées à plusieurs reprise.<br/> Dans cet exposé[…] -
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Séminaire
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Cryptographie
Conditional Reactive Simulatability (joint work with Michael
Orateur : Dennis Hofheinz - CWI Amsterdam
Simulatability has established itself as a salient notion for proving the security of multi-party protocols since it entails strong security and compositionality guarantees, which are achieved by universally quantifying over all environmental behaviors of the analyzed protocol. As a consequence, however, protocols that are secure except for certain environmental behaviors are not simulatable, even[…] -
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Séminaire
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Cryptographie
Constructing group based provably secure encryption schemes: a
Orateur : Maria Isabel Gonzalez Vasco - Universidad Rey Juan Carlos Madrid
Cryptographic primitives arising from group theory have in the last few years attracted a lot of attention. Unfortunately, up to date most of the existing proposals are still far away from practical applications, not only due to unlucky computational assumptions which later turned out to be invalid. In this talk we address the impact of modern security analysis in the sense of provable security to[…] -
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Séminaire
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Cryptographie
Relative rigid cohomology and the deformation method for elliptic curves
Orateur : Ralf Gerkmann - Universitat Mainz
By a well-known result of Dwork the zeta functions of the fibers in a one-parameter family of hypersurfaces can be described in terms of p-adic holomorphic functions. This result was used by A. Lauder in order to formulate a deter- ministic algorithm that computes the zeta function of a hypersurface in polynomial time. In this talk we describe a similiar method for elliptic curves which is based[…] -
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Séminaire
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Cryptographie
Symbolic verification of Diffie-Hellman-based group key exchange
Orateur : Yassine Lakhnech - VERIMAG
We discuss the cryptographic soundness of a symbolic model for Diffie-Hellman based key exchange protocols including symmetric encryption. Our main tool is a new dynamic variation of the decisional Diffie-Hellman problem useful for group protocols. -
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Séminaire
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Cryptographie
Some solved and open problems on Boolean functions
Orateur : Hans Dobbertin - Ruhr-Universität Bochum
We consider properties of Boolean functions which are important when they are used as components in cryptographic primitives. We focus mainly on non-linearity. Closely related issues are the weight distribution of BCH codes with two zeros and the crosscorrelation of two m-sequences. We shall present some recently solved old problems and the methods which where required to achieve this breakthrough[…] -