Table of contents

  • This session has been presented November 07, 2025 (13:45 - 14:45).

Description

  • Speaker

    Mingjie Chen - KU Leuven

In 2006, de Graaf et al. proposed a strategy based on Lie algebras for finding a linear transformation in the projective linear group that connects two linearly equivalent projective varieties defined over the rational numbers. Their method succeeds for several families of “classical” varieties, such as Veronese varieties, which are known to have large automorphism groups.

 

In this talk, we explain how to extend their Lie algebra method to finite fields, which introduces additional technical difficulties because of the positive characteristic. We show that the method works for Veronese varieties of dimension at least two over finite fields whose characteristic is greater than three and does not divide the dimension plus one.

 

We demonstrate that this leads to polynomial-time attacks against two candidate post-quantum key exchange protocols that are based on disguised Veronese surfaces and threefolds, which were recently proposed by Alzati et al. Furthermore, we provide strong evidence for the vulnerability of a digital signature scheme that relies on secant varieties of Grassmannians of projective lines, although for now this does not amount to a complete attack because the scheme operates over finite fields of characteristic two.

Practical infos

Next sessions

  • Wagner’s Algorithm Provably Runs in Subexponential Time for SIS^∞

    • November 21, 2025 (13:45 - 14:45)

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Johanna Loyer - Inria Saclay

    At CRYPTO 2015, Kirchner and Fouque claimed that a carefully tuned variant of the Blum-Kalai-Wasserman (BKW) algorithm (JACM 2003) should solve the Learning with Errors problem (LWE) in slightly subexponential time for modulus q = poly(n) and narrow error distribution, when given enough LWE samples. Taking a modular view, one may regard BKW as a combination of Wagner’s algorithm (CRYPTO 2002), run[…]

    • Cryptography

  • CryptoVerif: a computationally-sound security protocol verifier

    • November 28, 2025 (13:45 - 14:45)

    • Batiment 32B salle 12

    Speaker : Bruno Blanchet - Inria

    CryptoVerif is a security protocol verifier sound in the computational model of cryptography. It produces proofs by sequences of games, like those done manually by cryptographers. It has an automatic proof strategy and can also be guided by the user. It provides a generic method for specifying security assumptions on many cryptographic primitives, and can prove secrecy, authentication, and[…]

    • Cryptography

  • Structured-Seed Local Pseudorandom Generators and their Applications

    • December 05, 2025 (13:45 - 14:45)

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Nikolas Melissaris - IRIF

    We introduce structured‑seed local pseudorandom generators (SSL-PRGs), pseudorandom generators whose seed is drawn from an efficiently sampleable, structured distribution rather than uniformly. This seemingly modest relaxation turns out to capture many known applications of local PRGs, yet it can be realized from a broader family of hardness assumptions. Our main technical contribution is a[…]

    • Cryptography

  • Predicting Module-Lattice Reduction

    • December 19, 2025 (13:45 - 14:45)

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Paola de Perthuis - CWI

    Is module-lattice reduction better than unstructured lattice reduction? This question was highlighted as `Q8' in the Kyber NIST standardization submission (Avanzi et al., 2021), as potentially affecting the concrete security of Kyber and other module-lattice-based schemes. Foundational works on module-lattice reduction (Lee, Pellet-Mary, Stehlé, and Wallet, ASIACRYPT 2019; Mukherjee and Stephens[…]

    • Cryptography

Show previous sessions
Page top