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656 résultats

    • Séminaire

    • Cryptographie

    Conditional Reactive Simulatability (joint work with Michael

    • 17 mars 2006

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

    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[…]
    • Séminaire

    • Cryptographie

    Relative rigid cohomology and the deformation method for elliptic curves

    • 18 novembre 2005

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

    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[…]
    • Séminaire

    • Cryptographie

    Constructing group based provably secure encryption schemes: a

    • 28 avril 2006

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

    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[…]
    • Séminaire

    • Cryptographie

    Symbolic verification of Diffie-Hellman-based group key exchange

    • 13 janvier 2006

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

    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.
    • Séminaire

    • Cryptographie

    On Lattices, Learning with Errors, Random Linear Codes, and Cryptography

    • 07 octobre 2005

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

    Orateur : Oded Regev - Tel Aviv University

    Our main result is a reduction from worst-case lattice problems such as SVP and SIVP to a certain learning problem. This learning problem is a natural extension of the `learning from parity with error' problem to higher moduli. It can also be viewed as the problem of decoding from a random linear code. This, we believe, gives a strong indication that these problems are hard. Our reduction, however[…]
    • Séminaire

    • Cryptographie

    Traçace de traîtres face à des pirates adapatifs

    • 10 mars 2006

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

    Orateur : 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[…]