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Séminaire
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Cryptographie
Towards Trustworthy Electronic Voting Systems
Orateur : Jacques Traoré - France telecom
We will focus on this talk on electronic voting which emulates traditional voting in a networked environment. We will first introduce the model of electronic voting. In particular, we will present the security requirements that an electronic voting system must fulfil in order to be a proper substitute for a paper-ballot system. We will also briefly review the cryptographic tools generally used to[…] -
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Séminaire
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Cryptographie
RSA problems with Lattice Reduction
Orateur : Alexander May - Technische Universität Darmstadt
This survey addresses the problems of factoring and inverting the RSA function. We define practically relevant relaxed instances of these problems that can be solved in polynomial time. These problem instances are modelled by polynomial equations with small roots. In order to recover the roots, we make use of a method due to Coppersmith which is in turn based on the famous LLL lattice reduction.[…] -
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Séminaire
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Cryptographie
An infinite class of balanced functions with optimal algebraic
Orateur : Claude Carlet - Université Paris 8
Travail en commun avec Keqin Feng, Tsinghua University, Pékin.<br/> After the improvement by Courtois and Meier of the algebraic attacks on stream ciphers and the introduction of the related notion of algebraic immunity, several constructions of infinite classes of Boolean functions with optimum algebraic immunity have been proposed. All of them gave functions whose algebraic degrees are high[…] -
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Séminaire
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Cryptographie
Quelques aspects algorithmiques de la cryptographie
Orateur : David Lubicz - DGA et Université Rennes I
La cryptographie à clef publique, qui fut inventée dans les années soixante-dix par W. Diffie et M. Hellman, apporte par rapport à la cryptographie symétrique un certain nombre de fonctionnalités particulièrement intéressantes pour les applications pratiques. Sa mise en oeuvre repose le plus souvent sur la difficulté calculatoire de certains problèmes issus de la théorie des nombres. De là, on[…] -
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Séminaire
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Cryptographie
Breaking the F-FCSR-H stream cipher in real time
Orateur : Thomas Johanson - Lund University
The F-FCSR stream cipher family has been presented a few years ago. Apart from some flaws in the initial propositions, corrected in a later stage, there are no known weaknesses of the core of these algorithms. The hardware oriented version, called FCSR-H, is one of the ciphers selected for the eSTREAM portfolio. In this paper we present a new and severe cryptanalytic attack on the F-FCSR stream[…] -
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Séminaire
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Cryptographie
Key Recovery Attacks of Practical Complexity on AES Variants With Up To 10 Rounds
Orateur : Orr Dunkelman - ENS
AES is the best known and most widely used block cipher. Its three versions (AES-128, AES-192, and AES-256) differ in their key sizes (128 bits, 192 bits and 256 bits) and in their number of rounds (10, 12, and 14, respectively). In the case of AES-128, there is no known attack which is faster than the 2^{128} complexity of exhaustive search. However, AES-192 and AES-256 were recently shown to be[…] -