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    • Seminar

    • Cryptography

    On Fast Algebraic Attacks

    • June 25, 2004

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

    Speaker : Frederik Armknecht - Universitat Mannheim

    An algebraic attack is a method for cryptanalysis which is based on finding and solving a system of nonlinear equations. Recently, algebraic attacks where found helpful in cryptanalysing stream ciphers based on linear feedback shift registers. The efficiency of these attacks greatly depends on the degree of the nonlinear equations.<br/> At Crypto 2003, Courtois proposed fast algebraic attacks. The[…]
    • Seminar

    • Cryptography

    Basing Cryptography on Biometrics and Other Noisy Data

    • March 18, 2005

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

    Speaker : Yevgeniy Dodis - New York Univeristy

    We provide formal definitions and efficient secure techniques for - turning biometric and other noisy data into keys usable for *any* cryptographic application, and - reliably and securely authenticating biometric data. Our techniques apply not just to biometric information, but to any keying material that, unlike traditional cryptographic keys, is (1) not reproducible precisely and (2) not[…]
    • Seminar

    • Cryptography

    On the Subexponentiality of the Elliptic Curve Discrete Logarithm Problem over Extension Fields

    • October 15, 2004

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

    Speaker : Clauss Diem - Universität Essen

    The purpose of the talk is to present the following heuristic result.<br/> Let a, b in R with 0 < a < b. Then discrete logarithms in E(F_q^n), where q is a prime power, a log_2(q) \leq n \leq b \log_2(q)$ and E/F_q^n is any elliptic curve over F_q^n, can be solved in probabilistic subexponential time L[3/4].<br/> The algorithm is a variant of a recent index calculus algorithm by Gaudry. The main[…]
    • Seminar

    • Cryptography

    Constructions in public-key cryptography over matrix groups

    • May 13, 2005

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

    Speaker : Ilia Ponomarenko - Université de Saint Petersbourg

    A new two-parties key agreement protocol based on identities in groups is proposed. For abelian groups this protocol is, in fact, the Diffie-Hellman one. We also discuss a general scheme producing matrix groups for which our protocol can have a secure realization.
    • Seminar

    • Cryptography

    Countermeasures Against Leaked-Emission Analysis for Curve-Based Cryptosystems

    • November 14, 2003

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

    Speaker : Roberto Avanzi - Universität Essen

    Power Analysis (and, more generally, Leaked-Emission Analysis) is a technique for guessing the flow of cryptographic algorithms implemented on embedded devices, in particular smart cards. If a single input is used, the process is referred to as a Simple Power Analysis (SPA), and if several different inputs are used together with statistical tools, it is called Differential Power Analysis (DPA).[…]
    • Seminar

    • Cryptography

    Preuves de sécurité pour le chiffrement asymétrique sans redondance

    • January 09, 2004

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

    Speaker : David Pointcheval - CNRS-ENS

    La confidentialité des messages est certainement le plus ancien des besoins en sécurité de l'information. Le concept de cryptographie asymétrique, proposé en 1976 par Diffie et Hellman, a provoqué un important bouleversement, aussi bien au niveau des fonctionnalités que de l'analyse de sécurité. Par exemple, avec la clé publique de son interlocuteur, il est possible de lui envoyer un message[…]