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Séminaire
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Cryptographie
Breaking the F-FCSR-H stream cipher in real time
Orateur : Thomas Johanson - Lund University
The F-FCSR stream cipher family has been presented a few years ago. Apart from some flaws in the initial propositions, corrected in a later stage, there are no known weaknesses of the core of these algorithms. The hardware oriented version, called FCSR-H, is one of the ciphers selected for the eSTREAM portfolio. In this paper we present a new and severe cryptanalytic attack on the F-FCSR stream[…] -
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Séminaire
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Cryptographie
Key Recovery Attacks of Practical Complexity on AES Variants With Up To 10 Rounds
Orateur : Orr Dunkelman - ENS
AES is the best known and most widely used block cipher. Its three versions (AES-128, AES-192, and AES-256) differ in their key sizes (128 bits, 192 bits and 256 bits) and in their number of rounds (10, 12, and 14, respectively). In the case of AES-128, there is no known attack which is faster than the 2^{128} complexity of exhaustive search. However, AES-192 and AES-256 were recently shown to be[…] -
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Séminaire
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Cryptographie
Hardware Operators for Pairing-Based Cryptography
Orateur : Jean-Luc Beuchat - University of Tsukuba
This talk is devoted to the design of fast parallel accelerators for the cryptographic Tate pairing. We propose here a novel hardware implementation of Miller's loop based on a pipelined Karatsuba-Ofman multiplier. Thanks to a careful choice of the mean of computing the Tate pairing and algorithms for tower field arithmetic, we manage to keep the pipeline busy. We also describe the strategies we[…] -
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Séminaire
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Cryptographie
Algebraic Analysis of MinRank
Orateur : Françoise Levy-dit-Vehel - ENSTA
We here investigate the hardness of one of the most relevant problems in multivariate cryptography, namely MinRank: given non-negative intgers n,k,r, and matrices M_0,...,M_k, of size n with entries in F_q, decide whether there exists an F_q-linear combination of those matrices which has rank less than or equal to r. Our starting point is the Kipnis-Shamir modeling of the problem. We first prove[…] -
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Séminaire
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Cryptographie
Opérateurs matériels pour la cryptographie basée sur les
Orateur : Jérémie Detrey - LORIA
Introduits initialement dans le domaine de la cryptographie par Menezes, Okamoto & Vanstone (1993) puis Frey & Rück (1994) pour attaquer le problème du logarithme discret sur certaines courbes elliptiques, les couplages sont depuis quelques années à la base de nombreux protocoles utiles en cryptographie tels que la signature numérique courte ou la cryptographie basée sur l'identité. L'évaluation[…] -
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Séminaire
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Cryptographie
Computing isogenies of small degrees on Abelian Varieties
Orateur : Damien Robert - LORIA
Isogenies are an essential tool in Elliptic Curves cryptography, where they are used in a wide variety of area: fast point counting, complex multiplication methods... Velu's formulas give an efficient method for computing such isogenies, but there are no formula known for curves of higher genera or general abelian varieties (except some special case for isogenies of degree 2). In this talk we will[…] -