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721 results
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Seminar
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Cryptography
Design and Analysis of Opaque Signatures
Speaker : Laila El Aimani - Technicolor
Digital signatures were introduced to guarantee the authenticity and integrity of the underlying messages. However, and in situations where the signed data is commercially or personally sensitive, the universal verification of digital signatures is undesirable, and needs to be limited or controlled. Therefore, mechanisms which share most properties with digital signatures except the universal[…] -
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Seminar
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Cryptography
Explicit isogenies of low degree
Speaker : Kiminori Tsukazaki - University of Warwick
There are several algorithms for computing isogenies between elliptic curves, and one of them is Elkies' method using the modular curve. Motivated by that, we will look at an algebraic approach to explicitly compute isogenies of degree p for certain small primes p between elliptic curves, by using the modular curve and 'generic kernel polynomials'. -
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Seminar
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Cryptography
Key Recovery Attacks on 3-round Even-Mansour
Speaker : Itai Dinur - ENS
The Even-Mansour (EM) encryption scheme received a lot of attention in the last couple of years due to its exceptional simplicity and tight security proofs. The original $1$-round construction was naturally generalized into $r$-round structures with one key, two alternating keys, and completely independent keys.<br/> In this talk I will describe the first key recovery attack on the one-key 3-round[…] -
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Seminar
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Cryptography
Utilisation des symétries pour la résolution du problème de
Speaker : Louise Huot - LIP6
Récemment Diem et Gaudry ont introduit indépendemment une méthode de résolution du DLP sur les courbes elliptiques définies sur un corps fini non premier K, de degré d'extension n > 1 sur le corps de base k. Cet algorithme repose sur le principe général du calcul d'indice. Une étape cruciale de cet algorithme nécessite de décomposer des points de la courbe E(K) selon une base de facteurs. C'est à[…] -
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Seminar
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Cryptography
Algorithmique détendue pour les nombres entiers p-adiques
Speaker : Grégoire Lecerf - CNRS
Les implantations actuelles des nombres p-adiques reposent souvent sur des techniques dites zélées qui demandent de connaître à l'avance la précision nécessaire pour les calculs. Cette approche est très efficace du point de vue de la complexité asymptotique et elle est largement utilisée, par exemple dans des algorithmes de remontée de type Newton-Hensel intervenant dans la factorisation des[…] -
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Seminar
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Cryptography
Multiplication by n on elliptic curves over rings
Speaker : Jinbi Jin - Leiden university
Division polynomials express multiples of *affine* points on Weierstrass elliptic curves over fields. The restriction to affine points becomes an issue with elliptic curves over arbitrary rings, where it may happen that there are multiple 'points at infinity'. We will explain how a modification of the classical division polynomials describes multiplication on all points of Weierstrass elliptic[…] -