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633 résultats

    • Séminaire

    • Cryptographie

    Locally recoverable codes from curves

    • 20 octobre 2017

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

    Orateur : Everett Howe - Center for Communications Research, San Diego

    A locally recoverable code, or LRC, is a code over a finite alphabet such that the value of any single coordinate of a codeword can be recovered from the values of a small subset of other coordinates. I will explain why LRCs are important for applications such as cloud data storage, and I will present several constructions of locally recoverable codes from Galois covers of curves over finite[…]
    • Séminaire

    • Cryptographie

    Improving greedy nonrandomness detectors for stream ciphers

    • 24 mars 2017

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

    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[…]
    • Séminaire

    • Cryptographie

    Class Group Computations in Number Fields and Applications to Cryptology

    • 08 décembre 2017

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

    Orateur : Alexandre Gelin - Versailles-Saint-Quentin-en-Yvelines

    In this talk, we focus on class group computations in number fields. We start by describing an algorithm for reducing the size of a defining polynomial of a number field. There exist infinitely many polynomials that define a specific number field, with arbitrarily large coefficients, but our algorithm constructs the one that has the absolutely smallest coefficients. The advantage of knowing such a[…]
    • Séminaire

    • Cryptographie

    Tightly Secure CCA-Secure Encryption without Pairings.

    • 25 novembre 2016

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

    Orateur : Romain Gay - ENS

    (Joint work with Dennis Hofheinz, Eike Kiltz and Hoeteck Wee) We present the first CCA-secure public-key encryption scheme based on DDH where the security loss is independent of the number of challenge ciphertexts and the number of decryption queries. Our construction extends also to the standard k-Lin assumption in pairing-free groups, whereas all prior constructions starting with Hofheinz and[…]
    • Séminaire

    • Cryptographie

    Adaptive Oblivious Transfer with Access Control for NC1 from LWE

    • 16 juin 2017

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

    Orateur : Fabrice Mouhartem - Ens Lyon

    Adaptive oblivious transfer (OT) is a protocol where a sender initially commits to a database M_1, …, M_N. Then, a receiver can query the sender up to k times with private indexes ρ_1, …, ρ_k so as to obtain M_{ρ_1}, …, M_{ρ_k} and nothing else. Moreover, for each i ∈ [k], the receiver’s choice ρ_i may depend on previously obtained messages {M_{ρ_j}}_{j< i} . Oblivious transfer with access control[…]
    • Séminaire

    • Cryptographie

    Short McEliece key from algebraic geometry codes with automorphism

    • 26 janvier 2018

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

    Orateur : elise barelli - INRIA Saclay

    In 1978, McEliece introduced a public key encryption scheme based on linear codes and suggested to use classical Goppa codes, ie: subfield subcodes of algebraic geometric (AG) codes built on a curve of genus 0. This proposition remains secure and in order to have a generalization of classical Goppa codes, in 1996, H. Janwa and O. Moreno suggested to use subfield subcode of AG codes, which we call[…]