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657 results

    • Seminar

    • Cryptography

    Quantum complexity of the knapsack problem

    • November 19, 2004

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

    Speaker : Alexandre Kazakov

    An analogue quantum computer for the solution of the knapsack problem is discussed. Dynamics of some quantum-optical system exhibits explicit parallels with knapsack problem. This fact gives the possibility to propose an quantum algorithm for the knapsack problem and to estimate the quantum complexity of this problem.
    • Seminar

    • Cryptography

    Packings on the Grassmann manifold: an interesting approach for non coherent space-time coding

    • November 21, 2003

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

    Speaker : Jean-Claude Belfiore - ENST

    The need of high data rates on the radio channel (WiFi and its future for example) explains the increasing number of researchers working on space-time codes. Preparing Wireless IP systems, some companies and some researchers are promoting the use of non coherent space-time codes.<br/> We show that designing a non coherent space-time code is equivalent to finding some good packings on the Grassmann[…]
    • Seminar

    • Cryptography

    Efficient arithmetic on (hyper-)elliptic curves over finite fields

    • April 04, 2003

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

    Speaker : Tanja Lange - Ruhr-Universität Bochum

    The talk will be concerned with arithmetic on elliptic and hyperelliptic curves. We show how fast the arithmetic can get by clever choices of the coordinates and present special kinds of curves which allow even faster arithmetic using the Frobenius endomorphism. For elliptic curves this has been used to achieve fast arithmetic for the past years. However, so far arithmetic in the ideal class group[…]
    • Seminar

    • Cryptography

    Sur le calcul du corps de définition d'un point de torsion d'une jacobienne d'une courbe de genre quelconque

    • January 23, 2004

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

    Speaker : Bas Edixhoven - Leiden University

    En commençant par un calcul explicite sur une courbe elliptique, j'expliquerai ma stratégie pour calculer le corps de définition d'un point de torsion d'une jacobienne d'une courbe de genre quelconque. En gros, cette stratégie consiste à calculer le polynôme minimal d'une coordonnée d'un tel point par une approximation (complexe ou p-adique) avec une précision suffisante. J'expliquerai comment la[…]
    • Seminar

    • Cryptography

    Constructive Galois Theory

    • September 12, 2003

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

    Speaker : Juergen Klueners - Universität Kassel

    In constructive Galois theory, there are two main questions: the direct problem and the inverse problem. For the inverse problem the question is whether it is possible to find a polynomial such that the Galois group of that polynomial is a given finite group. In this talk, we will focus on the direct problem. Given a polynomial f we explain how to compute the Galois group of this polynomial. The[…]
    • Seminar

    • Cryptography

    Arithmétique des courbes elliptiques et hyperelliptiques en cryptographie

    • March 07, 2003

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

    Speaker : Sylvain Duquesne - Université de Bordeaux, projet AREHCC

    Nous nous interessons dans cet exposé à l'aspect arithmétique de la cryptographie elliptique et hyperelliptique. Nous verrons comment obtenir une arithmétique la plus rapide possible, en particulier au niveau de la multiplication scalaire, qui est l'opération de base dans les protocoles cryptographiques fondés sur les courbes. Nous nous interesserons aux cas où le corps de base est $F_p$ ou $F_{2[…]