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655 results

    • Seminar

    • Cryptography

    Protecting security protocols against guessing attacks: towards

    • April 07, 2006

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

    Speaker : Mathieu Baudet - ENS Cachan

    Designing secure protocols based on passwords is a difficult task. Indeed, passwords, and more generally low-entropy secrets, are potentially vulnerable to guessing attacks, that is, exhaustive, "brute force" searches. Preventing guessing attacks typically requires a protocol to conceal any partial information on the password (e.g. its checksum) which could help the attacker confirm his guess[…]
    • 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

    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

    Constructing elliptic curves by p-adic methods

    • May 07, 2004

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

    Speaker : Peter Stevenhagen - University of Leiden

    We will discuss a p-adic method to construct an elliptic curve over a finite field such that the group of rational points over the base field has some prescribed order N. The method uses ideas of Couveignes-Henocq, and is being developed and improved by my PhD student Reinier Broker.
    • Seminar

    • Cryptography

    Preuves interactives de théorèmes et développement de programmes certifiés

    • December 03, 2004

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

    Speaker : Pierre Castéran - LABRI

    L'exposé se veut une introduction à l'assistant de démonstration Coq, ( http://coq.inria.fr ) ainsi qu'au formalisme sur lequel se base cet outil : le Calcul des Constructions Inductives. Des exemples, empruntés aux mathématiques ou a l'algorithmique, montreront la puissance d'expression de ce formalisme.
    • Seminar

    • Cryptography

    Rigid cohomology and point counting on varieties over finite fields

    • March 11, 2005

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

    Speaker : Ralf Gerkmann - Universitat Erlangen

    n 2001 K. Kedlaya suggested an algorithm to compute the zeta function of a hyperelliptic curve over a finite field of small odd characteristic. The basic idea of his approach is to compute the explicit Frobenius action on the Monsky-Washniter cohomology in dimension one. Later his method was extended by P. Gaudry and N. Guerel to superelliptic curve and by J. Denef and F. Vercauteren to[…]