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655 results

    • Seminar

    • Cryptography

    Cryptanalyse algébrique de DAGS

    • September 27, 2019

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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:[…]
    • Seminar

    • Cryptography

    Grost Distinguishing Attack: A new rebound attack of an AES-like permutation

    • March 02, 2018

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Victor Cauchois - DGA et IRMAR

    Grostl est une fonction de hachage finaliste de la compétition SHA-3. Elle est dotée d'une preuve de sécurité qui assure sa résistance aux attaques en collision, pré-image et seconde pré-image sous l'hypothèse que deux permutations internes sont idéales. Ces permutations, 14 tours d'un SPN, calques de l'AES, présentent une structure sensible aux attaques rebond. Ces attaques sont des attaques[…]
    • Seminar

    • Cryptography

    Discrete logarithm computation in finite fields GF(p^k) with NFS

    • March 01, 2019

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Aurore Guillevic - INRIA

    Pairings on elliptic curves are involved in signatures, NIZK, and recently in blockchains (ZK-SNARKS).<br/> These pairings take as input two points on an elliptic curve E over a finite field, and output a value in an extension of that finite field. Usually for efficiency reasons, this extension degree is a power of 2 and 3 (such as 12,18,24), and moreover the characteristic of the finite field has[…]
    • Seminar

    • Cryptography

    Post-quantum cryptography based on supersingular isogeny problems?

    • October 25, 2019

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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[…]
    • Seminar

    • Cryptography

    Learning Strikes Again: the Case of the DRS Signature Scheme

    • November 09, 2018

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Yu Yang - CWI Amsterdam

    Lattice signature schemes generally require particular care when it comes to preventing secret information from leaking through signature transcript. For example, the Goldreich-Goldwasser-Halevi (GGH) signature scheme and the NTRUSign scheme were completely broken by the parallelepiped-learning attack of Nguyen and Regev (Eurocrypt 2006). Several heuristic countermeasures were also shown[…]
    • Seminar

    • Cryptography

    Homomorphic Signatures on Randomizable Ciphertexts

    • May 10, 2019

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    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[…]