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655 results
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Seminar
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Cryptography
Conditional Reactive Simulatability (joint work with Michael
Speaker : 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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Seminar
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Cryptography
La sécurité des schémas de Feistel aléatoires
Speaker : 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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Seminar
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Cryptography
Constructing group based provably secure encryption schemes: a
Speaker : 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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Seminar
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Cryptography
Relative rigid cohomology and the deformation method for elliptic curves
Speaker : 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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Seminar
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Cryptography
Symbolic verification of Diffie-Hellman-based group key exchange
Speaker : 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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Seminar
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Cryptography
Traçace de traîtres face à des pirates adapatifs
Speaker : Thomas Sirvent - CELAR-IRMAR
Les schémas de traçage de traîtres sont utilisés pour lutter contre le piratage lorsqu'on souhaite envoyer de manière sécurisée des données à de nombreux utilisateurs : si certains utilisateurs se rassemblent et partagent leurs clés secrètes pour fabriquer un décodeur pirate, une procédure de traçage doit permettre de trouver au moins l'un de ces ``traîtres'' à partir du décodeur pirate, auquel on[…] -