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Accueil du site > Séminaires et journées internes > Séminaires de CRYPTO

Séminaires CRYPTO 2018-2019

Agenda

séminaire

    • Mardi 11 décembre 11:00-12:00 - Simon Masson - Thalès

      Cocks–Pinch curves of embedding degrees five to eight and ate pairing computation

      Résumé : 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 degrees 5 to 8 ; we extend the Cocks–Pinch algorithm to obtain pairing-friendly curves with an efficient ate pairing. We carefully select our curve parameters so as to thwart possible attacks by "special" or "tower" Number Field Sieve algorithms. We target a 128-bit security level, and back this security claim by computation time estimates for the DLP computation. We also compare the efficiency of the ate pairing computation on these curves to k = 12 curves (Barreto–Naehrig, Barreto–Lynn–Scott), k = 16 curves (Kachisa–Schaefer–Scott) and k = 1 curves (Chatterjee–Menezes– Rodríguez-Henríquez).

      Lieu : bât. Descartes, salle 301


    • Vendredi 14 décembre 15:00-16:00 - Luca De Feo - UVSQ

      Exploring Isogeny Graphs – HDR defense

      Résumé : Motivated by the recent applications of isogeny graphs in cryptography, we review topics related to isogenies of elliptic curves defined over finite fields, and their computations.
      Isogeny graphs come in two families : complex multiplication (CM) and supersingular. CM graphs enjoy a rich structure, related to the theory of the orders of an imaginary quadratic field. We explain how this theory yields practical algorithms to move "vertically" in the graphs, along the lattice of quadratic orders.
      However, "practical" does not imply "easy". In order to efficiently implement our algorithms, we shall review the available methods to compute in the algebraic closure of a finite field. Interestingly, isogenies will also turn out to be useful for these algorithms, their computation thus becoming both a goal and a tool.
      Finally, we will review the application of isogeny graphs to cryptographic key exchange. CM graphs will offer a natural generalization of the classical Diffie–Hellman key exchange, a fact already recognized twenty years ago, and recently revamped. The structure of supersingular graphs, on the other hand, is related to the maximal orders of a quaternion algebra, and is harder to handle algorithmically ; only recently these graphs have been proposed as a foundation for cryptography.
      In both cases, the security of the cryptographic protocols is based on the difficulty of moving "horizontally" in the isogeny graphs. We shall thus conclude our study with a review of the known algorithms, both classical and quantum, to solve these problems.

      Lieu : bât. Descartes, Amphi B


    • Mardi 22 janvier 2019 11:00-12:00 - Fabrice Rouiller - IMJ

      TBA

      Lieu : TBA


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Séminaire dédié à la cryptographie et à la sécurité informatique. Ce séminaire, ouvert à tous, a généralement lieu le mardi matin de 11h à 12h en salle 301 du bâtiment Descartes.

Pour intervenir dans celui-ci, en présentant vos recherches ou vos développements industriels, veuillez contacter Luca De Feo.
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Mots-clés

Cryptographie