511 résultats
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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.[…] -
Fountain codes
Orateur : Amin Shokrollahi - EPFL
A Fountain code is a code of fixed dimension and a limitless block-length. This is a new class of codes with very interesting applications. In this talk I will show how Fountain codes can be applied to the problem of reliable, robust, and speedy transmission of data over a heterogeneous network from one or multiple transmitters to one or multiple receivers. I will then talk about applications to[…] -
Courbes elliptiques et applications cryptographiques à la diffusion numérique sécurisée
Orateur : Thomas Sirvent - IRMAR
L'objet de cette thèse est la diffusion numérique sécurisée réalisée à l'aide de courbes elliptiques. Elle se compose de quatre chapitres :<br/> Le premier chapitre est consacré au calcul de points de l-torsion sur une courbe elliptique définie sur un corps fini de caractéristique p. Plus précisément, nous combinons un algorithme rapide de calcul d'isogénies dû à Bostan,[…] -
Stream Ciphers - Now and Then
Orateur : Emilia Kasper - Katholieke Universiteit Leuven
In November 2004, the European Network of Excellence for Cryptology (ECRYPT) launched a call for new stream cipher primitives. Authors from academia as well as industry submitted 34 designs, and in May 2008, 8 ciphers were chosen for the eSTREAM final portfolio. In this talk, we look back at the history of stream ciphers to understand the design choices made by cryptographers today. We start by[…] -
The probability that a F_q-hypersurface is smooth
Orateur : Jeroen Demeyer - Universiteit Gent
Consider the projective space P^n over a finite field F_q. A hypersurface is defined by one homogenous equation with coefficients in F_q. For d going to infinity, we show that the probability that a hypersurface of degree d is nonsingular approaches 1/\zeta_{P^n (n+1)}. This is analogous to the well-known fact that the probability that an integer is squarefree equals 1/\zeta(2) = 6/\pi^2. This[…] -
Binary Edwards curves
Orateur : Tanja Lange - Technische Universiteit Eindhoven
The curve shape suggested by Edwards does not define elliptic curves over fields of characteristic 2. We recently generalized the concept of Edwards curves and defined binary Edwards curves. These curves offer complete addition formulas and are the first binary curves with this property. Doubling and differential addition (addition of two points with known difference, like in the Montgomery[…]