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673 résultats

    • Séminaire

    • Cryptographie

    A heuristic quasi-polynomial algorithm for discrete logarithm

    • 03 octobre 2014

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

    Orateur : Razvan Basbulescu - LORIA

    in finite fields of small characteristic The difficulty of discrete logarithm computations in fields GF(q^k) depends on the relative sizes of k and q. Until recently all the cases had a sub-exponential complexity of type L(1/3), similar to the complexity of factoring. If n is the bit-size of q^k, then L(1/3) can be approximated by 2^(n^(1/3)). In 2013, Joux designed a new algorithm for constant[…]
    • Séminaire

    • Cryptographie

    Beyond the black and grey box

    • 25 avril 2014

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

    Orateur : Yoni De Mulder - University of Leuven

    In the white-box attack context, i.e., the setting where an implementation of a cryptographic algorithm is executed on an untrusted open platform, the adversary has full access to the implementation and its execution environment. As a result, the adversary is much more powerful than in a traditional black-box environment in which the adversary has only access to the inputs and outputs of a[…]
    • Séminaire

    • Cryptographie

    Cryptanalysis of Round-Reduced PRINCE and TWINE

    • 27 mars 2015

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

    Orateur : Patrick Derbez - Luxembourg

    NXP Semiconductors and its academic partners challenged the cryptographic community with finding practical attacks on the block cipher they designed, PRINCE. In the first part of this talk we present new attacks on round-reduced PRINCE including the ones which won the challenge in the 6 and 8-round categories --- the highest for which winners were identified. Our first attacks rely on a meet-in[…]
    • Séminaire

    • Cryptographie

    Cyclic and quasi-cyclic separable Goppa codes

    • 14 novembre 2014

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

    Orateur : Sergey Bezzateev - Université d'État de Saint-Pétersbourg

    Overview of recent results in constructions of cyclic and quasi-cyclic Goppa codes. Classical and generalized Goppa codes are considered. Subclasses of embedded optimal quasi-cyclic Goppa codes with improvement parameters are presented.
    • Séminaire

    • Cryptographie

    Chiffrement (complètement) homomorphe : de la théorie à la pratique

    • 20 juin 2014

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

    Orateur : Tancrède Lepoint - CryptoExperts

    Le chiffrement complètement homomorphe (parfois considéré comme le Saint Graal de la cryptographie) permet d'effectuer (de façon publique) des calculs arbitraires sur des messages chiffrés. Les premières instanciations de cette surprenante primitive ne peuvent être considérées comme pratiques, chaque multiplication de deux bits chiffrés nécessitant d'être suivie par une procédure de plusieurs[…]
    • Séminaire

    • Cryptographie

    Keep your friends close with distance-bounding protocols

    • 07 février 2014

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

    Orateur : Maria Cristina Onete - IRISA

    Authentication protocols, run between a prover and a verifier, allow the verifier to check the legitimacy of the prover. A legitimate prover should always authenticate (the correctness requirement), while illegitimate parties (adversaries) should not authenticate (the soundness or impersonation resistance requirement). Secure authentication protocols thwart most Man-in-the-Middle (MIM) attacks,[…]