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633 results
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Seminar
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Cryptography
The first practical calculations: congruences for Ramanujan's tau function mod 13
Speaker : Johan Bosma - Leiden University
We will describe how we are implementing Edixhoven's method for computing polynomials for the mod l Galois representations associated to modular forms. The computations are done in MAGMA, using modular symbols and numerical analysis. Recently, we have computed such polynomials for the mod 13 representation associated to Delta, the discriminant modular form of weight 12. In that case, we work with[…] -
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Seminar
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Cryptography
Generic Homomorphic Undeniable Signatures
Speaker : Serge Vaudenay - EPFL
We introduce a new computational problem related to the interpolation of group homomorphisms which generalizes many famous cryptographic problems including discrete logarithm, Diffie-Hellman, and RSA. As an application, we propose a generic undeniable signature scheme which generalizes the MOVA schemes. Our scheme is generic in the sense that we transform a private group homomorphism from public[…] -
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Seminar
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Cryptography
Propriétés cryptographiques des fonctions booléennes symétriques
Speaker : Marion Videau - INRIA Rocquencourt
Les fonctions booléennes symétriques sont les fonctions dont la valeur ne dépend que du poids du vecteur d'entrée. Ces fonctions peuvent être représentées plus simplement, que ce soit par leur forme algébrique normale ou leur vecteur des valeurs, que des fonctions booléennes générales --- vecteurs de taille (n+1) contre des vecteurs de taille 2^{n} en général. En outre, ces fonctions ont une[…] -
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Seminar
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Cryptography
Algebraic attacks and design of block ciphers, stream ciphers, and multivariate public key schemes
Speaker : Nicolas Courtois - Schlumberger
Following the famous 1949 paper of Shannon, breaking a "good" cipher should require: "as much work as solving a system of simultaneous equations in a large number of unknowns of a complex type". For most practical cryptosystems, the problem of recovering the key can indeed can be seen as solving a huge system of binary nonlinear equations. In general, solving such a problem is known to be NP-hard,[…] -
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Seminar
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Cryptography
Quantum complexity of the knapsack problem
Speaker : Alexandre Kazakov
An analogue quantum computer for the solution of the knapsack problem is discussed. Dynamics of some quantum-optical system exhibits explicit parallels with knapsack problem. This fact gives the possibility to propose an quantum algorithm for the knapsack problem and to estimate the quantum complexity of this problem. -
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Seminar
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Cryptography
Packings on the Grassmann manifold: an interesting approach for non coherent space-time coding
Speaker : Jean-Claude Belfiore - ENST
The need of high data rates on the radio channel (WiFi and its future for example) explains the increasing number of researchers working on space-time codes. Preparing Wireless IP systems, some companies and some researchers are promoting the use of non coherent space-time codes.<br/> We show that designing a non coherent space-time code is equivalent to finding some good packings on the Grassmann[…] -