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Séminaire
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Cryptographie
Computing isogenies from modular equations in genus 2
Orateur : Jean Kieffer - Université Bordeaux 1
Given two l-isogenous elliptic curves, a well-known algorithm of Elkies uses modular polynomials to compute this isogeny explicitly. In this work, we generalize his ideas to Jacobians of genus 2 curves. Our algorithms works for both l-isogenies and (in the RM case) cyclic isogenies, and uses Siegel or Hilbert type modular equations respectively. This has applications for point counting in genus 2:[…] -
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Séminaire
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Cryptographie
Key recovery from partial information
Orateur : Gabrielle De Michelli - UC San Diego
The security of deployed protocols not only relies on the hardness of the underlying mathematical problem but also on the implementation of the algorithms involved. Many fast modular exponentiation algorithms have piled up over the years and some implementations have brought vulnerabilities that are exploitable by side-channel attacks, in particular cache attacks.<br/> In this talk, we consider[…] -
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Séminaire
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Cryptographie
Traceable Constant-Size Multi-Authority Credentials
Orateur : Chloé Hébant - ENS
Many attribute-based anonymous credential (ABC) schemes have been proposed allowing a user to prove the possession of some attributes, anonymously. They became more and more practical with, for the most recent papers, a constant-size credential to show a subset of attributes issued by a unique credential issuer. However, proving possession of attributes coming from K different credential issuers[…] -
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Séminaire
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Cryptographie
Wave: A New Code-Based Signature Scheme
Orateur : Thomas Debris-alazard - inria
It is a long standing open problem to build an efficient and secure digital signature scheme based on the hardness of decoding a linear code which could compete with widespread schemes like DSA or RSA. The latter signature schemes are broken by a quantum computer with Shor’s algorithm. Code-based schemes could provide a valid quantum resistant replacement. We present here Wave the first « hash[…] -
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Séminaire
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Cryptographie
Supersingular isogeny Diffie-Hellman
Orateur : Leonardo Colo - Univesité Aix-Marseille
Supersingular isogeny graphs have been used in the Charles–Goren–Lauter cryptographic hash function and the supersingular isogeny Diffie–Hellman (SIDH) protocole of De\,Feo and Jao. A recently proposed alternative to SIDH is the commutative supersingular isogeny Diffie–Hellman (CSIDH) protocole, in which the isogeny graph is first restricted to $\FF_p$-rational curves $E$ and $\FF_p$-rational[…] -
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Séminaire
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Cryptographie
Key Reinstallation Attacks: Forcing Nonce Reuse in WPA2
Orateur : Mathy Vanhoef - KU-Leuven
We introduce key reinstallation attacks (KRACKs). These attacks abuse features of a protocol to reinstall an already in-use key, thereby resetting nonces and/or replay counters associated to this key. We show that our novel attack technique breaks several handshakes that are used in a WPA2-protected network.<br/> All protected Wi-Fi networks use the 4-way handshake to generate fresh session keys.[…] -