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633 résultats
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Séminaire
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Cryptographie
Class Group Computations in Number Fields and Applications to Cryptology
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[…] -
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Séminaire
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Cryptographie
Adaptive Oblivious Transfer with Access Control for NC1 from LWE
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[…] -
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Séminaire
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Cryptographie
Short McEliece key from algebraic geometry codes with automorphism
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[…] -
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Séminaire
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Cryptographie
Tightly Secure CCA-Secure Encryption without Pairings.
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[…] -
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Séminaire
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Cryptographie
Low-Complexity Cryptographic Hash Functions
Orateur : Vinod Vaikuntanathan - Massachusetts Institute of Technology
Cryptographic hash functions are efficiently computable functions that shrink a long input into a shorter output while achieving some of the useful security properties of a random function. The most common type of such hash functions is collision resistant hash functions (CRH), which prevent an efficient attacker from finding a pair of inputs on which the function has the same output.<br/> Despite[…] -
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Séminaire
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Cryptographie
Middle-Product Learning With Errors
Orateur : Miruna Rosca - ENS de Lyon
We introduce a new variant MP-LWE of the Learning With Errors problem (LWE) making use of the Middle Product between polynomials modulo an integer q. We exhibit a reduction from the Polynomial-LWE problem (PLWE) parametrized by a polynomial f, to MP-LWE which is defined independently of any such f. The reduction only requires f to be monic with constant coefficient coprime with q. It incurs a noise[…] -