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Séminaire
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Cryptographie
Packings on the Grassmann manifold: an interesting approach for non coherent space-time coding
Orateur : 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[…] -
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Séminaire
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Cryptographie
Efficient arithmetic on (hyper-)elliptic curves over finite fields
Orateur : Tanja Lange - Ruhr-Universität Bochum
The talk will be concerned with arithmetic on elliptic and hyperelliptic curves. We show how fast the arithmetic can get by clever choices of the coordinates and present special kinds of curves which allow even faster arithmetic using the Frobenius endomorphism. For elliptic curves this has been used to achieve fast arithmetic for the past years. However, so far arithmetic in the ideal class group[…] -
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Séminaire
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Cryptographie
Sur le calcul du corps de définition d'un point de torsion d'une jacobienne d'une courbe de genre quelconque
Orateur : Bas Edixhoven - Leiden University
En commençant par un calcul explicite sur une courbe elliptique, j'expliquerai ma stratégie pour calculer le corps de définition d'un point de torsion d'une jacobienne d'une courbe de genre quelconque. En gros, cette stratégie consiste à calculer le polynôme minimal d'une coordonnée d'un tel point par une approximation (complexe ou p-adique) avec une précision suffisante. J'expliquerai comment la[…] -
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Séminaire
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Cryptographie
Research on Cryptographic Algorithms: beyond triple-DES, AES and RSA
Orateur : Bart Preneel - University of Leuven
In this talk we discuss the state of the art and progress in cryptographic algorithms such as encryption algorithms and digital signature techniques. We present at a high level the challenges to the designers (and users) of cryptographic algorithms and we discuss the major components of the solution, that is, research, standardization, and open evaluation. We also discuss the status of the NESSIE[…] -
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Séminaire
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Cryptographie
Monsky-Washnitzer Cohomology and Computing Zeta Functions
Orateur : Kiran Kedlaya - Berkeley
Monsky-Washnitzer cohomology is a p-adic cohomology theory for algebraic varieties over finite fields, based on algebraic de Rham cohomology. Unlike the l-adic (etale) cohomology, it is well-suited for explicit computations, particularly over fields of small characteristic. We describe how to use Monsky-Washnitzer to construct efficient algorithms for computing zeta functions of varieties over[…] -
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Séminaire
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Cryptographie
Galois Groups of Additive Polynomials
Orateur : Heinrich Matzat - Universitaet Heidelberg
Additive polynomials over a field $ F$ of characteristic $ p>0$ have the form $ f(X)=\sum\limits^m_{k=0} a_k X^{p^k}$ with $ a_k \in F$. In case $ a_0 \neq 0$ they are Galois polynomials with an $ \mathbb{F}_p$-vector space of solutions, and any finite Galois extension $ E$ over $ F$ can be generated by such an additive polynomial.<br/> The Galois group of $ f(X)$ or $ E/F$ , respectively, acts[…] -