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687 results

    • Seminar

    • Cryptography

    Horizontal isogeny graphs of ordinary abelian varieties and the discrete logarithm problem

    • February 09, 2018

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

    Speaker : Benjamin WESOLOWSKI - École Polytechnique Federale de Lausanne

    An isogeny graph is a graph whose vertices are abelian varieties (typically elliptic curves, or Jacobians of genus 2 hyperelliptic curves) and whose edges are isogenies between them. Such a graph is "horizontal" if all the abelian varieties have the same endomorphism ring. We study the connectivity and the expander properties of these graphs. We use these results, together with a recent algorithm[…]
    • Seminar

    • Cryptography

    Number Systems and Cryptography, some examples

    • February 08, 2019

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

    Speaker : Jean-Claude Bajard - Sorbonne Université

    Number systems are behind a lot of implementations. The role of representation is often underrated while its importance in implementation is crucial. We survey here some classes of fundamental systems that could be used in crypotgraphy. We present three main categories:<br/> - systems based on the Chinese Remainder Theorem which enter more generally in the context of polynomial interpolation,<br/[…]
    • Seminar

    • Cryptography

    Post-quantum cryptography based on supersingular isogeny problems?

    • October 25, 2019

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

    Speaker : Christophe Petit - University of Birmingham

    The security of many cryptographic protocols in use today relies on the computational hardness of mathematical problems such as integer factorization. These problems can be solved using quantum computers, and therefore most of our security infrastructures will become completely insecure once quantum computers are built. Post-quantum cryptography aims at developing security protocols that will[…]
    • Seminar

    • Cryptography

    Practical Strategy-Resistant Privacy-Preserving Elections

    • October 19, 2018

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

    Speaker : Quentin Santos - Orange

    Recent advances in cryptography promise to let us run com- plex algorithms in the encrypted domain. However, these results are still mostly theoretical since the running times are still much larger than their equivalents in the plaintext domain. In this context, Majority Judgment is a recent proposal for a new voting system with several interesting practical advantages, but which implies a more[…]
    • Seminar

    • Cryptography

    Quantum security of the Fiat-Shamir transform of commit and open protocols

    • April 26, 2019

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

    Speaker : André Chailloux - INRIA

    Applying the Fiat-Shamir transform on identification schemes is one of the main ways of constructing signature schemes. While the classical security of this transformation is well understood, there are still many cases for which we do not know whether the quantum security holds or not. In this paper, we show that if we start from a commit-and-open identification scheme, where the prover first[…]
    • Seminar

    • Cryptography

    Aggregate Cash Systems: A Cryptographic Investigation of Mimblewimble

    • November 30, 2018

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

    Speaker : Michele Orru - ENS