627 results

  • Sanitization of FHE Ciphertexts

    • February 12, 2016

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

    Speaker : Damien Stehlé - ENS Lyon

    By definition, fully homomorphic encryption (FHE) schemes support homomorphic decryption, and all known FHE constructions are bootstrapped from a Somewhat Homomorphic Encryption (SHE) scheme via this technique. Additionally, when a public key is provided, ciphertexts are also re-randomizable, e.g. by adding to them fresh encryptions of~$0$. From those two operations we devise an algorithm to[…]
  • Finding ECM-Friendly Curves through a Study of Galois Properties

    • January 29, 2016

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

    Speaker : Cyril Bouvier - Institut de mathématiques de Bordeaux

    In this talk, I'll prove some divisibility properties of the cardinality of elliptic curve groups modulo primes. These proofs explain the good behavior of certain parameters when using Montgomery or Edwards curves in the setting of the elliptic curve method (ECM) for integer factorization. The ideas behind the proofs can be used to find new infinite families of elliptic curves with good division[…]
  • Algorithms for polynomial selection in the number field sieve

    • December 18, 2015

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

    Speaker : Shi Bai - Australian National University

    The general number field sieve (GNFS) is the most efficient algorithm known for factoring large integers. It consists of several stages, the first one being polynomial selection. The running-time of the number field sieve depends on the quality of the chosen polynomials. The quality of the chosen polynomials can be modeled in terms of size and root properties. In this talk, we will describe some[…]
  • Certification de représentations galoisiennes modulaires

    • December 11, 2015

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

    Speaker : Nicolas Mascot - Université de Bordeaux 1

    Nous verrons comment certifier algorithmiquement des calculs de représentations galoisiennes associés à des formes modulaires, en nous appuyant notamment sur le théorème de Khare-Wintenberger (ex conjecture de modularité de Serre) et des calculs de cohomologie des groupes afin de déterminer le groupe de Galois de certains polynômes.
  • Soutenance de thèse

    • December 04, 2015

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

    Speaker : Gwezheneg Robert - Rennes 1

    Le codage espace-temps désigne les codes correcteurs mis en place pour les transmissions MIMO. (Ce sont des transmissions sans fil utilisant plusieurs antennes, en émission comme en réception.) Ces codes correcteurs ont la particularité d'avoir des coefficients dans le corps des complexes, et non dans des corps finis. Un des paramètres fondamentaux pour l'évaluation des performances des codes[…]
  • Algebraic Decoding of Folded Gabidulin Codes

    • November 27, 2015

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

    Speaker : Hannes Bartz - Technische Universität München

    Folded Gabidulin codes were proposed by Mahdavifar and Vardy in 2012. Beside the code construction an interpolation-based decoding scheme that can correct rank errors beyond the unique decoding radius for low code rates was presented.<br/> In this talk we present an efficient interpolation-based decoding algorithm for folded Gabidulin codes that can correct rank errors beyond half the minimum rank[…]