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685 results
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Seminar
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Cryptography
A heuristic quasi-polynomial algorithm for discrete logarithm
Speaker : Razvan Basbulescu - LORIA
in finite fields of small characteristic The difficulty of discrete logarithm computations in fields GF(q^k) depends on the relative sizes of k and q. Until recently all the cases had a sub-exponential complexity of type L(1/3), similar to the complexity of factoring. If n is the bit-size of q^k, then L(1/3) can be approximated by 2^(n^(1/3)). In 2013, Joux designed a new algorithm for constant[…] -
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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
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[…] -
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Seminar
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Cryptography
Same-Values Analysis on Elliptic Curve Cryptography
Speaker : Cédric Murdica - Secure-IC
Elliptic Curve Cryptography (ECC) is believed to be unbreakable in the black box model, where the cryptanalyst has access to inputs and outputs only. However, it is not enough if the cryptosystem is embedded on a device that is physically accessible to potential attackers. In addition to inputs and outputs, the attacker can study the physical behaviour of the device such as the execution time or[…] -
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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
Une solution du problème "Isomorphisme de polynômes à deux
Speaker : Jérôme Plût - ANSSI
Le problème d'isomorphisme de polynômes à deux secrets (IP2S) pour m=2 variables sur un corps k est le suivant: étant données deux familles a, b de deux polynômes quadratiques chacune, trouver deux applications linéaires bijectives s, t telles que b = t ° a ° s. Nous donnons un algorithme permettant de calculer s, t en un temps O(n^4) pour toutes les instances.<br/> Le problème IP2S a été[…] -