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Séminaire
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Cryptographie
Optimisation des Principaux Composants des Chiffrements par Bloc
Orateur : Baptiste Lambin - soutenance de thèse salle Métivier à l'IRISA, 14h
La sécurité des chiffrements par bloc évolue constamment au fur et à mesure que de nouvelles techniques de cryptanalyse sont découvertes. Lors de la conception de nouveaux chiffrements par bloc, il est donc nécessaire de considérer ces nouvelles techniques dans l'analyse de sécurité. Dans cette thèse, nous montrons comment construire certaines opérations internes des chiffrements par bloc pour[…] -
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Séminaire
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Cryptographie
New candidate PRFs and their applications
Orateur : Alain Passelègue - Inria
In this talk, I will present new and simple candidate PRFs introduced in a recent work. In this work, we depart from the traditional approaches for building PRFs used in provable security or in applied cryptography by exploring a new space of plausible PRF candidates. Our guiding principle is to maximize simplicity while optimizing complexity measures that are relevant to advanced cryptographic[…] -
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Séminaire
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Cryptographie
Zero-Knowledge Argument for Matrix-Vector Relations and Lattice-Based Group Encryption
Orateur : Fabrice Mouhartem - ENS Lyon
Group encryption (GE) is the natural encryption analogue of group signatures in that it allows verifiably encrypting messages for some anonymous member of a group while providing evidence that the receiver is a properly certified group member. Should the need arise, an opening authority is capable of identifying the receiver of any ciphertext. As intro- duced by Kiayias, Tsiounis and Yung […] -
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Séminaire
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Cryptographie
Improving greedy nonrandomness detectors for stream ciphers
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[…] -
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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
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[…] -