Description
Dilithium is a signature algorithm, considered post-quantum, and recently standardized under the name ML-DSA by NIST. Due to its security and performance, it is recommended in most use cases.
During this presentation, I will outline the main ideas behind two studies, conducted in collaboration with Andersson Calle-Vierra, Benoît Cogliati, and Louis Goubin, which provide a better understanding of Dilithium's practical security.
I show that by introducing an error during the generation of the Dilithium signature, it is possible to force the signer to provide “incorrect” signatures that reveal information about the secret key in the form of inequalities on its coefficients. We then reformulate the problem of recovering the secret key from incorrect signatures into a linear programming problem.
Among the data in the MLWE instance (A,t), which is at the heart of Dilithium's construction, the least significant part of t—denoted by t0—is not included in the public key and is formally considered part of the secret key. Knowing t_0 has no impact on Dilithium's black box security, but it does allow for much more effective side-channel attacks. I explain the main ideas for constructing an attack that finds t0 from Dilithium signatures, again by twisting linear programming tools.
Both of these results use linear programming techniques that are somewhat deviated from their traditional uses, which is quite unusual for cryptanalysis of public-key algorithms.
Infos pratiques
Prochains exposés
-
Cyclotomic Cosets: Hidden Subgroup and Quantum Sieving Algorithm for Prime-Power Moduli
Orateur : Mathias Boucher - Université de Rennes
The Dihedral Coset Problem (DCP), also known as the hidden shift problem, plays a fundamental role in post-quantum public-key cryptography, since the Learning-With-Error problem reduces to DCP. The “Simon meets Kuperberg” quantum algorithm by Bonnetain and Naya-Plasencia solves the DCP in quasi-polynomial time when the modulus is a power of two. We provide a generalization of this algorithm for[…] -
Adelic reduction of module lattices
Orateur : Henry Bambury - DGA-MI et Inria Rennes
We give a strict generalisation of the LLL algorithm over number fields, based on the reduction theory of $GL(n)$ over the adele ring of a number field. Our algorithm is free of heuristics, with rigorous bounds on output quality and complexity. -- based on joint work with Seungki Kim, Changmin Lee and Phong Nguyen ---
Cryptography
-
-
European Cyber Week: atelier cryptographie post-quantique
Dans la continuité des éditions 2021, 2022 et 2024, la DGA — en partenariat avec CREACH LABS et avec le soutien de l'ANSSI, de l'IRISA, de l'IRMAR et du Pôle d'Excellence Cyber — organise la 4e édition de l'atelier consacré à la cryptographie post-quantique dans le cadre de l'European Cyber Week 2026. Attention, il faut s'inscrire (gratuitement) au préalable — s'inscrire à la conférence Les[…] -
Post-quantum day of the cryptography seminar
A scientific day devoted to post-quantum cryptography, held in the wake of the European Cyber Week, with talks more technical than those presented at the ECW. The talks will take place at Amphi E in building 02A. To register for lunch, please do so before oct 30th using this link. -
Chiffrement homomorphe à l'aide des groupes après Nuida
Orateur : Pierre Guillot - Ravel Technologies/Université de strasbourg
Nuida et d'autres ont montré comment on peut obtenir un protocole de chiffrement pleinement homomorphe si l'on sait chiffrer les éléments d'un groupe G convenable, tout en sachant faire l'opération de G "en homomorphe". Les exemples étaient jusqu'à présent limités au chiffrement d'un bit à la fois, avec beaucoup d'opérations à effectuer pour "simuler" les portes logiques usuelles. Je vais[…]-
Cryptography
-
-
TBD
Orateur : Dung Bui - Northwestern University
-
Nouveaux doctorants
Exposés courts des nouveaux doctorants (Elouan, Quentin, Eliot)