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723 results

    • Seminar

    • Cryptography

    Disjunctions for Hash Proof Systems: New Constructions and Applications

    • April 24, 2015

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

    Speaker : Fabrice Ben Hamouda - ENS

    Hash Proof Systems were first introduced by Cramer and Shoup (Eurocrypt'02) as a tool to construct efficient chosen-ciphertext-secure encryption schemes. Since then, they have found many other applications, including password authenticated key exchange, oblivious transfer, and zero-knowledge arguments. One of the aspects that makes hash proof systems so interesting and powerful is that they can be[…]

    • Seminar

    • Cryptography

    Multiplication by n on elliptic curves over rings

    • October 26, 2012

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

    Speaker : Jinbi Jin - Leiden university

    Division polynomials express multiples of *affine* points on Weierstrass elliptic curves over fields. The restriction to affine points becomes an issue with elliptic curves over arbitrary rings, where it may happen that there are multiple 'points at infinity'. We will explain how a modification of the classical division polynomials describes multiplication on all points of Weierstrass elliptic[…]

    • Seminar

    • Cryptography

    Keccak

    • June 04, 2013

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

    Speaker : Joan Daemen - ST Micro

    In October 2012, the American National Institute of Standards and Technology (NIST) announced the selection of Keccak as the winner of the SHA-3 Cryptographic Hash Algorithm Competition. This concluded an open competition that was remarkable both for its magnitude and the involvement of the cryptographic community. Public review is of paramount importance to increase the confidence in the new[…]

    • Seminar

    • Cryptography

    Verification of Security Protocols with Lists:

    • January 11, 2013

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

    Speaker : Miriam Paiola - ENS

    We present a novel, simple technique for proving secrecy properties for security protocols that manipulate lists of unbounded length, for an unbounded number of sessions.<br/> More specifically, our technique relies on the Horn clause approach used in the automatic verifier ProVerif: we show that if a protocol is proven secure by our technique with lists of length one, then it is secure for lists[…]

    • Seminar

    • Cryptography

    Calculs de cup-produits et comptage de points.

    • October 11, 2013

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

    Speaker : François-Renaud Escriva - Vrije Universiteit Amsterdam

    Dans cet exposé, nous présentons un algorithme de comptage de points qui repose sur le calcul de certains cup-produits. Notre algorithme se fonde, comme l'algorithme de Kedlaya, sur le calcul de la matrice de l'action d'un Frobenius semi-linéaire sur le premier groupe de cohomologie d'une courbe. Cependant, notre algorithme a l'avantage de pouvoir s'appliquer à une classe très générale de courbes[…]

    • Seminar

    • Cryptography

    Analysis of BKZ

    • May 27, 2011

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

    Speaker : Xavier Pujol - ENS Lyon

    Strong lattice reduction is the key element for most attacks against lattice-based cryptosystems. Between the strongest but impractical HKZ reduction and the weak but fast LLL reduction, there have been several attempts to find efficient trade-offs. Among them, the BKZ algorithm introduced by Schnorr and Euchner in 1991 seems to achieve the best time/quality compromise in practice. However, no[…]
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