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Séminaire
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Cryptographie
Horizontal isogeny graphs of ordinary abelian varieties and the discrete logarithm problem
Orateur : Benjamin WESOLOWSKI - École Polytechnique Federale de Lausanne
An isogeny graph is a graph whose vertices are abelian varieties (typically elliptic curves, or Jacobians of genus 2 hyperelliptic curves) and whose edges are isogenies between them. Such a graph is "horizontal" if all the abelian varieties have the same endomorphism ring. We study the connectivity and the expander properties of these graphs. We use these results, together with a recent algorithm[…] -
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Séminaire
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Cryptographie
CSIDH: an efficient post-quantum commutative group action
Orateur : Chloé Martindale - Technical University of Eindhoven
CSIDH, or `commutative supersingular isogeny Diffie-Hellman' is a new isogeny-based protocol of Castryck, Lange, Martindale, Panny, and Renes.<br/> The Diffie-Hellman style scheme resulting from the group action allows for public key validation at very little cost, runs reasonably fast in practice, and has public keys of only 64 bytes at a conjectured AES-128 security level, matching NIST’s post[…] -
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Séminaire
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Cryptographie
Isogeny-based cryptography from superspecial genus-2 curves
Orateur : Wouter Castryck - KU Leuven
I will report on some first attempts to do isogeny-based cryptography in genus 2. More precisely, we will use isogeny graphs of superspecial principally polarized abelian surfaces over GF(p^2) for constructing variants of Charles, Goren and Lauter's hash function and of Jao and De Feo's SIDH key exchange protocol, both of which use supersingular elliptic curves over GF(p^2). This will be largely[…] -
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Séminaire
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Cryptographie
Zero-Knowledge Argument for Matrix-Vector Relations and Lattice-Based Group Encryption
Orateur : Fabrice Mouhartem - ENS Lyon
Group encryption (GE) is the natural encryption analogue of group signatures in that it allows verifiably encrypting messages for some anonymous member of a group while providing evidence that the receiver is a properly certified group member. Should the need arise, an opening authority is capable of identifying the receiver of any ciphertext. As intro- duced by Kiayias, Tsiounis and Yung […] -
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Séminaire
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Cryptographie
New candidate PRFs and their applications
Orateur : Alain Passelègue - Inria
In this talk, I will present new and simple candidate PRFs introduced in a recent work. In this work, we depart from the traditional approaches for building PRFs used in provable security or in applied cryptography by exploring a new space of plausible PRF candidates. Our guiding principle is to maximize simplicity while optimizing complexity measures that are relevant to advanced cryptographic[…] -
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Séminaire
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Cryptographie
Tunnels sécurisés pour environnements contraints
Orateur : Loic Ferreira - soutenance de thèse salle Métivier à l'IRISA, 14h30
Avec l’extension de l’Internet des Objets et l’usage croissant de terminaux à bas coût, de nombreux protocoles de sécurité sont déployés à grande échelle. Cette thèse étudie le champ des protocoles d’échange de clé authentifié basés sur des fonctions cryptographiques symétriques. Nous montrons que les protocoles existants n’atteignent pas un niveau de sécurité correspondant à l’état de l’art en[…] -