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Séminaire
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Cryptographie
Attaques par invariants : comment choisir les constantes de tour pour s'en protéger
Orateur : Anne Canteaut - Inria
Many lightweight block ciphers apply a very simple key schedule in which the round keys only differ by addition of a round-specific constant. Generally, there is not much theory on how to choose appropriate constants. In fact, several of those schemes were recently broken using invariant attacks, i.e. invariant subspace or nonlinear invariant attacks. This work analyzes the resistance of such[…] -
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Séminaire
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Cryptographie
Calcul de r-isogénies à l'aide de la \ell-torsion.
Orateur : Cyril Hugounenq - Université de Versailles
Après des rappels sur les courbes elliptiques et les isogénies, on va présenter le problème que l'on veut résoudre: soit deux courbes elliptiques E,E' définies sur un corps fini (de caractéristique p) que l'on sait r-isogénes alors on souhaite calculer la r-isogénie qui les relie. De nombreux algorithmes ont résolu ce problème par le passé notamment l'algorithme de Couveignes de 1996 qui sera[…] -
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Séminaire
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Cryptographie
Middle-Product Learning With Errors
Orateur : Miruna Rosca - ENS de Lyon
We introduce a new variant MP-LWE of the Learning With Errors problem (LWE) making use of the Middle Product between polynomials modulo an integer q. We exhibit a reduction from the Polynomial-LWE problem (PLWE) parametrized by a polynomial f, to MP-LWE which is defined independently of any such f. The reduction only requires f to be monic with constant coefficient coprime with q. It incurs a noise[…] -
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Séminaire
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Cryptographie
New multilinear maps over the integers
Orateur : Jean-Sébastien Coron - Université du Luxembourg
In the last few years, cryptographic multilinear maps have proved their tremendous potential as building blocks for new constructions, in particular the first viable approach to general program obfuscation. After the first candidate construction by Garg, Gentry and Halevi (GGH) based on ideal lattices, a second construction over the integers was described by Coron, Lepoint and Tibouchi (CLT).[…] -
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Séminaire
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Cryptographie
Finding ECM-Friendly Curves through a Study of Galois Properties
Orateur : 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[…] -
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