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633 results

    • Seminar

    • Cryptography

    On weak keys in QC-MDPC schemes

    • February 21, 2020

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

    Speaker : Valentin Vasseur - INRIA

    Quasi-cyclic moderate density parity check (QC-MDPC) codes allow the design of McEliece-like public-key encryption schemes with compact keys and a security that provably reduces to hard decoding problems for quasi-cyclic codes. Because of these features, QC-MDPC have attracted a lot of interest from the cryptographic community. In particular, the BIKE suite of key exchange mechanisms has been[…]
    • Seminar

    • Cryptography

    Soutenance de thèse: Theoretical Hardness of Algebraically Structured Learning With Errors

    • November 16, 2021

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

    Speaker : Katharina Boudgoust - Rennes

    The main focus of this PhD thesis lies on the computational problem Learning With Errors (LWE). It is a core building block of lattice-based cryptography, which itself is among the most promising candidates to replace current cryptographic protocols once large-scale quantum computers may be available. The contributions of the present work are separated into two different parts. First, we study the[…]
    • Seminar

    • Cryptography

    The generalized quaternion isogeny path problem.

    • April 03, 2020

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

    Speaker : 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[…]
    • Seminar

    • Cryptography

    Soutenance de thèse: Study and design of new encryption primitives based on rank metric error correcting codes

    • December 10, 2021

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

    Speaker : 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[…]
    • 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[…]