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634 résultats

    • Séminaire

    • Cryptographie

    Practical Strategy-Resistant Privacy-Preserving Elections

    • 19 octobre 2018

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

    Orateur : 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[…]
    • Séminaire

    • Cryptographie

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

    • 26 avril 2019

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

    Orateur : 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[…]
    • Séminaire

    • Cryptographie

    Aggregate Cash Systems: A Cryptographic Investigation of Mimblewimble

    • 30 novembre 2018

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

    Orateur : Michele Orru - ENS

    • Séminaire

    • Cryptographie

    Cocks-Pinch curves of embedding degree five to eight and optimal ate pairing computation

    • 21 juin 2019

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

    Orateur : Simon Masson - Loria, Nancy

    Recent algorithmic improvements of discrete logarithm computation in special extension fields threaten the security of pairing-friendly curves used in practice. A possible answer to this delicate situation is to propose alternative curves that are immune to these attacks, without compromising the efficiency of the pairing computation too much. We follow this direction, and focus on embedding[…]
    • Séminaire

    • Cryptographie

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

    • 09 février 2018

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

    Orateur : 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[…]
    • Séminaire

    • Cryptographie

    CSIDH: an efficient post-quantum commutative group action

    • 01 février 2019

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

    Orateur : Chloé Martindale - Technical University of Eindhoven

    CSIDH, or `commutative supersingular isogeny Diffie-Hellman' is a new isogeny-based protocol of Castryck, Lange, Martindale, Panny, and Renes.<br/> The Diffie-Hellman style scheme resulting from the group action allows for public key validation at very little cost, runs reasonably fast in practice, and has public keys of only 64 bytes at a conjectured AES-128 security level, matching[…]