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655 results

    • Seminar

    • Cryptography

    Conditional Reactive Simulatability (joint work with Michael

    • March 17, 2006

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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[…]
    • Seminar

    • Cryptography

    La sécurité des schémas de Feistel aléatoires

    • October 14, 2005

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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[…]
    • Seminar

    • Cryptography

    Constructing group based provably secure encryption schemes: a

    • April 28, 2006

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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[…]
    • Seminar

    • Cryptography

    Relative rigid cohomology and the deformation method for elliptic curves

    • November 18, 2005

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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[…]
    • Seminar

    • Cryptography

    Symbolic verification of Diffie-Hellman-based group key exchange

    • January 13, 2006

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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.
    • Seminar

    • Cryptography

    Traçace de traîtres face à des pirates adapatifs

    • March 10, 2006

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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[…]