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713 results
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Seminar
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Cryptography
Algorithms for polynomial selection in the number field sieve
Speaker : Shi Bai - Australian National University
The general number field sieve (GNFS) is the most efficient algorithm known for factoring large integers. It consists of several stages, the first one being polynomial selection. The running-time of the number field sieve depends on the quality of the chosen polynomials. The quality of the chosen polynomials can be modeled in terms of size and root properties. In this talk, we will describe some[…] -
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Seminar
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Cryptography
Symmetric Encryption Scheme adapted to Fully Homomorphic Encryption Scheme
Speaker : Pierrick Méaux - ENS Paris
Fully Homomorphic Encryption is a powerful cryptographic construction, enabling to securely compute all functions on encrypted data, and decrypt the result of the function applied on the real data.<br/> This construction allows to securely delegate computation, which is a very important property with the increasing of the Cloud computing. Many client-server applications are appearing, all needing[…] -
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Seminar
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Cryptography
GGHLite: More Efficient Multilinear Maps from Ideal Lattices
Speaker : Adeline Langlois - ENS Lyon
The GGH Graded Encoding Scheme (of Garg, Gentry and Halevi), based on ideal lattices, is the first plausible approximation to a cryptographic multilinear map. Unfortunately, using the security analysis the authors provided, the scheme requires very large parameters to provide security for its underlying encoding re-randomization process. Our main contributions are to formalize, simplify and[…] -
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Seminar
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Cryptography
Rencontre au milieu avec match box sur KATAN
Speaker : Brice Minaud - ANSSI
Les attaques par rencontre au milieu ont connu un regain d'intérêt notamment à cause des chiffrements légers, qui s'y prêtent mieux que les chiffrements traditionnels. Cela a amené au développement de nouvelles variantes et améliorations de ces attaques. On présente ici une nouvelle technique pour augmenter le nombre de tours couverts par une rencontre au milieu. On l'applique ensuite à une[…] -
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Seminar
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Cryptography
Attaques quantiques contre les chiffrements par bloc composés
Speaker : Marc Kaplan - Télécom ParisTech
Nous étudions l'amplification de la sécurité obtenue en composant des chiffrements par bloc indépendants. Dans le cas classique, l'attaque Meet-in-the-middle est une attaque générique contre ces constructions. Si le temps nécessaire pour briser un chiffrement par bloc est t, alors cette attaque permet de briser deux chiffrements par bloc en un temps seulement 2t, alors qu'un cryptographe naïf[…] -
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Seminar
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Cryptography
Broadcast encryption: combinatorial vs. algebraic methods
Speaker : Duong-Hieu Phan - ENS
We consider a generalisation of the encryption from "one-to-one'' to "one-to-many'' communication, i.e. broadcast encryption. The objective is to allow a center to send secret messages to a large number of receivers. The security notion in “one-to-many” communications needs to be extended beyond the notion of confidentiality in “one-to-one” encryption in order to meet practical requirements. Two[…] -