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762 résultats
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Séminaire
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Cryptographie
Isogenies over Hessian Model of Elliptic Curves
Orateur : Emmanuel Fouotsa - Université de Bamenda
In this talk we present explicit formulas for isogenies between elliptic curves in (twisted) Hessian form. We examine the numbers of operations in the base field to compute the formulas. In comparison with other isogeny formulas, we note that the obtained formulas for twisted Hessian curves have the lowest costs for processing the kernel and the X-affine formula has the lowest cost for processing[…] -
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Séminaire
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Cryptographie
The generalized quaternion isogeny path problem.
Orateur : Antonin Leroux - LIX
The correspondence between maximal orders in a quaternion algebra and supersingular elliptic curves has uncovered new perspectives in the field of isogeny-based cryptography. The KLPT algorithm of Kohel et al. in 2014 introduces an algorithm solving the quaternion isogeny path problem in polynomial time. Studying this problem has applications both constructive and destructive. It has allowed to[…] -
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Séminaire
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Cryptographie
Soutenance de thèse: Study and design of new encryption primitives based on rank metric error correcting codes
Orateur : Ba Duc Pham - Rennes
In 2005, Faure and Loidreau proposed a new rank-metric cryptosystem inspired from the Hamming metric scheme of Augot-Finiasz in 2003. In 2018, it was broken by the attack of Gaborit, Otmani and Kalachi. Recently, there are some attempts of repairing the Faure-Loidreau scheme, for example the work of Renner, Puchinger and Wachter–Zeh which is called LIGA. In this thesis, we also introduce a new[…] -
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Séminaire
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Cryptographie
Code-based postquantum cryptography : candidates to standardization
Orateur : Nicolas Sendrier - INRIA
At the third round of the NIST standardization process, three candidates remain with a security based on error correcting codes, all are key exchange mechanisms. We will explore them according to their security assumptions and properties. Among them, we find an historical scheme (Classic McEliece), as well as schemes using sparse and quasi-cyclic matrices (BIKE and HQC). We will examine pros and[…] -
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Séminaire
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Cryptographie
Soutenance de thèse: Problème du logarithme discret sur des courbes elliptiques
Orateur : Andy Russon - Rennes 1 et Orange
L’usage des courbes elliptiques en cryptographie s’est largement répandu pour assurer la sécurité des communications ou de transactions financières. Cela est dû notamment au fait que la sécurité repose sur la difficulté du problème du logarithme discret qui permet d’utiliser les courbes elliptiques avec des paramètres qui assurent une efficacité.<br/> Dans cette thèse, nous abordons principalement[…] -
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Séminaire
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Cryptographie
Lattice-based signatures: from construction to implementation
Orateur : Pauline Bert - soutenance de thèse, amphi P de l'ISTIC, 14h
Lattice-based cryptography is one of the major line of research to build post-quantum public key primitives. In this thesis, we discuss about digital signatures constructions and their implementation. We first describe a Fiat-Shamir transformation from an identification scheme using rejection sampling to a digital signature secure in the random oracle model. Then we describe an identity-based[…] -