627 résultats
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Improving greedy nonrandomness detectors for stream ciphers
Orateur : Paul Stankovski - Université de Lund
We consider the problem of designing distinguishers and nonrandomness detectors for stream ciphers using the maximum degree monomial test. We construct an improved algorithm to determine the subset of key and IV-bits used in the test. The algorithm is generic, and can be applied to any stream cipher. In addition to this, the algorithm is highly tweakable, and can be adapted depending on the[…] -
Coercion-resistant Internet voting made practical
Orateur : Jacques Traore - Orange Labs
Internet voting offers a better voting experience since voters can cast their votes from their computers or even smartphones. By eliminating the need to visit polling places, it may attract more voters and thus increase voter turnout. However, it is still not widely spread owing to many inherent concerns such as risks entailed by the lack of private polling booths. Indeed, this may ease coercion[…] -
Permutations complètes en caractéristique 2.
Orateur : Valentin Suder - Université de Versailles Saint-Quentin
Dans ce travail, nous nous intéressons aux permutations complètes, c’est-à-dire aux fonctions bijectives $x\mapsto f(x)$ telles que $x\mapsto f(x)+x$ soient aussi bijectives. Plus particulièrement, nous nous intéressons aux permutations complètes sur les corps finis $\mathbb{F}_{2^n}$. En caractéristique 2, la définition des permutations complètes coincide avec celle des orthomorphismes. Nous[…] -
Improved Cryptanalysis of Rank Metric Schemes Based on Gabidulin Codes.
Orateur : Hervé Talé Kalachi - Université de Rouen et Université de Yaoundé, Cameroun
In this presentation, we prove that any variant of the GPT cryptosystem which uses a right column scrambler over the extension field as advocated by the works of Gabidulin et al. with the goal to resist to Overbeck’s structural attack are actually still vulnerable to that attack. We show that by applying the Frobenius operator appropriately on the public key, it is possible to build a Gabidulin[…] -
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[…] -
Algebraic geometry meets microcontrollers: Efficient, compact key
Orateur : Ben Smith - Ecole polytechnique
This talk will describe how we have applied the theory of Kummer surfaces --classic objects in algebraic geometry-- to produce compact, high-speed software for secure key exchange and signatures on microcontrollers. This is joint work with Brian Chung, Craig Costello, Joost Renes, Peter Schwabe, and Lejla Batina.