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633 results
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Seminar
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Cryptography
Superimposed codes and related problems
Speaker : Miklos Ruszinko - MTA SZTAKI
A family of subsets is r-cover-free, if no set is covered by the union of r others. These families were introduced in coding theory by Kautz and Singleton (disjunctive codes, superimposed codes) in early sixties.<br/> Variants of these codes were later investigated by Erdos, Frankl and Furedi, Alon and Asodi, Szegedy and Vishvanathan, just to mention a few. These codes are useful in circuit[…] -
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Seminar
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Cryptography
Questions d'euclidianité dans les corps de nombres
Speaker : Jean-Paul Cerri - IECN et LORIA
Le but de cet exposé est de présenter de nouveaux résultats sur les minima et spectres euclidiens des corps de nombres, et ceci d'un point de vue à la fois algorithmique et théorique. Un problème très ancien en théorie des nombres consiste à savoir si un corps de nombres est euclidien, en particulier pour la norme. Lorsqu'on cherche à préciser les choses, on est amené naturellement à définir les[…] -
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Seminar
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Cryptography
Explicit higher dimensional 3-adic canonical lifting
Speaker : Robert Carls - Sydney University
Our talk is about joint work with D. Kohel and D. Lubicz. We prove equations having as solutions the theta null points of canonical lifts of ordinary abelian varieties over finite fields of characteristic 3. We describe an algorithm for 3-adic canonical lifting of ordinary abelian surfaces based on our formulas. The algorithm has been implemented in MAGMA. Examples of canonically lifted theta null[…] -
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Seminar
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Cryptography
The arithmetic of elliptic divisibility sequences
Speaker : Graham Everest - Norwich University
A very deep problem with the Mersenne and Fibonacci sequences asks if there are infinitely many prime terms. Bang and Carmichael have studied the simpler problem which asks when the terms have primitive divisors. In my seminar I study the analogous questions for elliptic divisibility sequences. -
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Seminar
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Cryptography
On the security of quantum cryptographic keys
Speaker : Robert Koenig - Cambridge University
The security of quantum key distribution protocols is often defined in terms of the information an adversary obtains by measuring his system. Such definitions are fundamentally flawed because of a locking property of the accessible information: Giving the adversary a single bit of information may increase the accessible information by more than one bit. We give examples of keys that are not[…] -
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Seminar
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Cryptography
Résistance des fonctions de hachage itérées à l'attaque par boomerang
Speaker : Antoine Joux - DGA & Université de Versaille
Les fonctions cryptographiques les plus répandues pour hacher des données de grandes tailles sont architecturées autour d'une fonction de compression dont le design possède de nombreux points communs avec celui des fonctions de chiffrement par blocs. Il est donc naturel d'étudier comment se généralisent les attaques connues pour le chiffrement au cas du hachage. Dans cet exposé, nous mettons ainsi[…] -