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Accueil du site > Séminaires et journées internes > Séminaires de CRYPTO

Séminaires CRYPTO 2018-2019

Agenda

séminaire

    • Lundi 25 février 11:00-12:00 - Albrecht Petzoldt - UVSQ

      Cryptanalysis of the HiMQ-3 Signature Scheme

      Résumé : The HiMQ-3 signature scheme is a very efficient multivariate signature scheme and was one of the first round candidates of the NIST post-quantum standardization process.
      In this talk we present a new attack against HiMQ-3, the so called singularity attack. The attack uses a large number of (message/signature) pairs to recover an equivalent private key, which allows an attacker to forge signatures for arbitrary messages.
      While our attack does not break the scheme completely, it shows that the security claims of the authors are not correct.

      Lieu : bât. Descartes, salle 301


    • Lundi 4 mars 11:00-12:00 - Andre Schrottenloher - Inria Paris

      Optimal Merging Trees in Quantum k-xor Algorithms

      Résumé : The generalized birthday problem, or k-xor problem, has many applications in cryptography. Interestingly, there is a gap between its provable query complexity and its best known time complexity, obtained with Wagner’s algorithm. Quantum algorithms for this problem have been studied by Grassi et al. in 2018, with a similar gap remaining. In this work, we answer most of the open questions they left, thanks to a general unified framework ("merging trees") of which the algorithms of Grassi et al. are all special cases.
      Using Mixed Integer Linear Programming, we obtain the optimal time complexities for k-xor in this merging framework, and prove our observations for all values of k. Contrary to the classical case, where the complexity depends only on the biggest power of 2 included in k, Grassi and al. first observed an exponential quantum time separation between 2-xor and 3-xor. We extend this to all k and prove a separation between any pair of them in the quantum RAM model (also improving the case k = 3).
      When the quantum space complexity (number of qubits) is limited to linear, we obtain quantum time speedups on the classical k-xor for half of the values of k, improving also all previously known results. We also study the parallelization of merging trees.
      Finally, we extend this study to quantum multicollision search.

      Lieu : bât. Descartes, salle 301


    • Lundi 25 mars 11:00-12:00 - Claire Delaplace - Ruhr Uni Bochum

      TBA

      Lieu : bât. Descartes, salle 301


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Séminaire dédié à la cryptographie et à la sécurité informatique. Ce séminaire, ouvert à tous, a généralement lieu le lundi en salle 301 du bâtiment Descartes.

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Mots-clés

Cryptographie