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721 results

    • Seminar

    • Cryptography

    An infinite class of balanced functions with optimal algebraic

    • April 24, 2009

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

    Speaker : Claude Carlet - Université Paris 8

    Travail en commun avec Keqin Feng, Tsinghua University, Pékin.<br/> After the improvement by Courtois and Meier of the algebraic attacks on stream ciphers and the introduction of the related notion of algebraic immunity, several constructions of infinite classes of Boolean functions with optimum algebraic immunity have been proposed. All of them gave functions whose algebraic degrees are high[…]
    • Seminar

    • Cryptography

    Breaking the F-FCSR-H stream cipher in real time

    • January 16, 2009

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

    Speaker : Thomas Johanson - Lund University

    The F-FCSR stream cipher family has been presented a few years ago. Apart from some flaws in the initial propositions, corrected in a later stage, there are no known weaknesses of the core of these algorithms. The hardware oriented version, called FCSR-H, is one of the ciphers selected for the eSTREAM portfolio. In this paper we present a new and severe cryptanalytic attack on the F-FCSR stream[…]
    • Seminar

    • Cryptography

    Key Recovery Attacks of Practical Complexity on AES Variants With Up To 10 Rounds

    • September 25, 2009

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

    Speaker : Orr Dunkelman - ENS

    AES is the best known and most widely used block cipher. Its three versions (AES-128, AES-192, and AES-256) differ in their key sizes (128 bits, 192 bits and 256 bits) and in their number of rounds (10, 12, and 14, respectively). In the case of AES-128, there is no known attack which is faster than the 2^{128} complexity of exhaustive search. However, AES-192 and AES-256 were recently shown to be[…]
    • Seminar

    • Cryptography

    Formules efficaces pour les courbes de genre 2 à multiplication réelle.

    • October 12, 2007

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

    Speaker : Pierrick Gaudry - LORIA

    Les cryptosystèmes s'appuyant sur les courbes de genre 2 présentent des caractéristiques similaires au cas elliptique en terme de taille de clef, de bande passante, etc. En ce qui concerne les temps de calculs, cela dépend grandement des formules utilisées pour la loi de groupe. Dans cet exposé nous présenterons des formules efficaces pour les courbes de genre 2. Ces formules proviennent[…]
    • Seminar

    • Cryptography

    Calcul des valeurs des fonctions L p-adiques de corps

    • March 28, 2008

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

    Speaker : Xavier Roblot - Lyon1

    Suivant les travaux de Pi. Cassou-Noguès, D. Barsky, N. Katz et P. Colmez, je donnerai une construction explicite d'une fonction p-adique continue interpolant les valeurs aux entiers négatifs des fonctions L de Hecke de corps quadratiques réels. Je montrerai aussi comment cette construction permet de calculer les valeurs de cette fonction ou certaines expressions particulières.
    • Seminar

    • Cryptography

    Fountain codes

    • October 07, 2008

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

    Speaker : Amin Shokrollahi - EPFL

    A Fountain code is a code of fixed dimension and a limitless block-length. This is a new class of codes with very interesting applications. In this talk I will show how Fountain codes can be applied to the problem of reliable, robust, and speedy transmission of data over a heterogeneous network from one or multiple transmitters to one or multiple receivers. I will then talk about applications to[…]