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637 résultats

    • Séminaire

    • Cryptographie

    Computing isogenies from modular equations in genus 2

    • 10 janvier 2020

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

    Orateur : Jean Kieffer - Université Bordeaux 1

    Given two l-isogenous elliptic curves, a well-known algorithm of Elkies uses modular polynomials to compute this isogeny explicitly. In this work, we generalize his ideas to Jacobians of genus 2 curves. Our algorithms works for both l-isogenies and (in the RM case) cyclic isogenies, and uses Siegel or Hilbert type modular equations respectively. This has applications for point counting in genus 2:[…]
    • Séminaire

    • Cryptographie

    Key recovery from partial information

    • 01 octobre 2021

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

    Orateur : Gabrielle De Michelli - UC San Diego

    The security of deployed protocols not only relies on the hardness of the underlying mathematical problem but also on the implementation of the algorithms involved. Many fast modular exponentiation algorithms have piled up over the years and some implementations have brought vulnerabilities that are exploitable by side-channel attacks, in particular cache attacks.<br/> In this talk, we[…]
    • Séminaire

    • Cryptographie

    Constant time implementation of rank based cryptography

    • 01 avril 2022

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

    Orateur : Nicolas Aragon - IRISA

    Since the start of the NIST standardization project for post-quantum cryptography in 2017, rank metric based cryptography is becoming more popular as an alternative to code-based cryptography in the Hamming metric.<br/> While rank based cryptography has always been competitive in terms of keys and ciphertexts sizes, the lack of maturity in the implementations of these cryptosystems made them[…]
    • Séminaire

    • Cryptographie

    Improved Classical and Quantum Algorithms for Subset-Sum

    • 06 mars 2020

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

    Orateur : André Schrottenloher - INRIA

    We present new classical and quantum algorithms for solving random hard instances of the subset-sum problem, in which we are given n integers on n bits and try to find a subset of them that sums to a given target. This classical NP-complete problem has several applications in cryptography and underlies the security of some proposed post-quantum cryptosystems.<br/> At EUROCRYPT 2010, Howgrave[…]
    • Séminaire

    • Cryptographie

    Workshop mise en oeuvre de la cryptographie post-quantique

    • 17 novembre 2021

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

    Orateur : European CyberWeek - Rennes

    L'inscription est gratuite mais obligatoire, en particulier pour des raisons de jauges. Le nombre de places est limité. Le programme est disponible à l'adresse <a href="https://www.european-cyber-week.eu/cryptographie-post-quantique">https://www.european-cyber-week.eu/cryptographie-post-quantique</a><br/>
    • Séminaire

    • Cryptographie

    Comparing the difficulty of factorization and discrete logarithm: a 240-digit experiment

    • 10 avril 2020

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

    Orateur : Emmanuel Thomé - INRIA Nancy

    We report on two new records: the factorization of RSA-240, a 795-bit number, and a discrete logarithm computation over a 795-bit prime field. Previous records were the factorization of RSA-768 in 2009 and a 768-bit discrete logarithm computation in 2016. Our two computations at the 795-bit level were done using the same hardware and software, and show that computing a discrete logarithm is not[…]