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687 results
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Seminar
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Cryptography
Homomorphic Signatures on Randomizable Ciphertexts
Speaker : David Pointcheval - ENS
Anonymity is a primary ingredient for our digital life. Several tools have been designed to address it such as, for authentication, blind signatures, group signatures or anonymous credentials and, for confidentiality, randomizable encryption or mix-nets.<br/> When it comes to complex electronic voting schemes, random shuffling of ciphertexts with mix-nets is the only known tool. Such mix-nets are[…] -
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Seminar
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Cryptography
Soutenance de thèse (exceptionnellement jeudi à 14h): Couches de diffusion linéaires à partir de matrices MDS
Speaker : Victor Cauchois - DGA/Université Rennes 1
Cette thèse s’intéresse à deux aspects de la cryptologie symétrique liés à l’utilisation de matrices MDS dans les couches de diffusion linéaires de primitives. Une première partie se fonde sur les conceptions de couches de diffusion linéaires de schémas de chiffrement symétrique à partir de matrices MDS. Les associations entre matrices récursives, respectivement circulantes, et polynômes sont[…] -
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Seminar
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Cryptography
Cryptanalyse algébrique de DAGS
Speaker : Magali Bardet - université de Rouen
Elise Barelli et Alain Couvreur ont présenté une attaque dévastatrice sur le cryptosystème DAGS soumis au 1er tour de la compétition du NIST autour d'algorithmes de cryptographie post-quantiques. Je présenterai une explication précise de la résolution par bases de Gröbner de leur modélisation algébrique, expliquant l'efficacité de l'attaque pour les paramètres de DAGS publiés au NIST.<br/> lien:[…] -
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Seminar
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Cryptography
Horizontal isogeny graphs of ordinary abelian varieties and the discrete logarithm problem
Speaker : Benjamin WESOLOWSKI - École Polytechnique Federale de Lausanne
An isogeny graph is a graph whose vertices are abelian varieties (typically elliptic curves, or Jacobians of genus 2 hyperelliptic curves) and whose edges are isogenies between them. Such a graph is "horizontal" if all the abelian varieties have the same endomorphism ring. We study the connectivity and the expander properties of these graphs. We use these results, together with a recent algorithm[…] -
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Seminar
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Cryptography
Number Systems and Cryptography, some examples
Speaker : Jean-Claude Bajard - Sorbonne Université
Number systems are behind a lot of implementations. The role of representation is often underrated while its importance in implementation is crucial. We survey here some classes of fundamental systems that could be used in crypotgraphy. We present three main categories:<br/> - systems based on the Chinese Remainder Theorem which enter more generally in the context of polynomial interpolation,<br/[…] -
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Seminar
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Cryptography
Post-quantum cryptography based on supersingular isogeny problems?
Speaker : Christophe Petit - University of Birmingham
The security of many cryptographic protocols in use today relies on the computational hardness of mathematical problems such as integer factorization. These problems can be solved using quantum computers, and therefore most of our security infrastructures will become completely insecure once quantum computers are built. Post-quantum cryptography aims at developing security protocols that will[…] -