643 résultats
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Computing isogenies from modular equations in genus 2
Orateur : Jean Kieffer - Université Bordeaux 1
Given two l-isogenous elliptic curves, a well-known algorithm of Elkies uses modular polynomials to compute this isogeny explicitly. In this work, we generalize his ideas to Jacobians of genus 2 curves. Our algorithms works for both l-isogenies and (in the RM case) cyclic isogenies, and uses Siegel or Hilbert type modular equations respectively. This has applications for point counting in genus 2:[…] -
Divisible E-Cash from Constrained Pseudo-Random Functions
Orateur : Olivier Sanders - Orange
Electronic cash (e-cash) is the digital analogue of regular cash which aims at preserving users' privacy. Following Chaum's seminal work, several new features were proposed for e-cash to address the practical issues of the original primitive. Among them, divisibility has proved very useful to enable efficient storage and spendings. Unfortunately, it is also very difficult to achieve and, to date,[…] -
Intrusion Detection Systems over an Encrypted Traffic: Problem and Solutions
Orateur : Sébastien Canard (Orange)
Privacy and data confidentiality are today at the heart of many discussions. But such data protection should not be done at the detriment of other security aspects. In the context of network traffic, intrusion detection system becomes in particular totally blind when the traffic is encrypted, making clients again vulnerable to known threats and attacks. Reconciling security and privacy is then one[…] -
Présentation des fondamentaux du management du risque et d’EBIOS Risk Manager
Orateur : Vincent Loriot (ANSSI)
Résumé :a. Présentation ANSSIb. Tendances de la menace cyber et démarche pour s’en protégerc. Fondamentaux de la méthode EBIOS Risk ManagerLa présentation théorique sera complétée avec un atelier pratique couvrant les sujets suivants :a. Les besoins et enjeux de sécuritéb. Les couples Source de Risque / Objectif Viséc. La cartographie de menace de l’écosystème -
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[…] -
Considérations Pratiques sur les Compromis Temps-Mémoire Cryptanalytiques
Orateur : Florent Tardif - soutenance de thèse salle Métivier à l'IRISA, 14h30
Un compromis temps-mémoire cryptanalytique est une technique qui vise à réduire le temps nécessaire pour effectuer certaines attaques cryptographiques telles que l’inversion d’une fonction à sens unique. Une telle inversion intervient dans une des principales applications des compromis temps-mémoire : le cassage de mots de passe. La technique requiert un très lourd pré-calcul qui génère des tables[…]