Applied Crypto Group

LACS Seminar, April 13th, 2018, 11:00 AM, room MNO-E03-25-110, Belval Campus.

Benoit Cogliati. Provable security in symmetric cryptography

Abstract: Provable security is an essential part of both symmetric and public-key cryptography. Indeed, security proofs can increase confidence in the resistance of an algorithm against various types of attacks and justify its soundness. Moreover, theorems guide the choice of the security parameters in applications. In this context, tight security proofs are essential, since they prevent the use of unnecessarily high values for those parameters. In this talk, I will start by giving an overview of the indistinguishability notion and of the main theoretical models that are considered in symmetric cryptography. I will then illustrate these notions by presenting several results on the design of tweakable block ciphers, and on the construction of provably secure MACs based on block ciphers and tweakable block ciphers.

LACS Seminar, November 22nd, 2017, 10:30 AM, room MNO-E03-25-110, Belval Campus.

Tancrede Lepoint. Post-Quantum Cryptography using Module Lattices

Abstract: Recent advances in quantum computing and the announcement by the National Institute of Standards and Technology (NIST) to define new standards for digital-signature, encryption, and key-establishment protocols, spurred on the design and analysis of many post-quantum cryptographic schemes. One of the most efficient quantum-resilient alternatives for the above basic primitives is that of lattice cryptography.

Many lattice cryptography schemes are based on the learning-with-error problem over a ring. Past works have described digital signature schemes, encryption schemes, and key encapsulation mechanisms in one of two ways. Either they set the ring as Z_q[x]/(x^n+1) or as Z_q^n. The former choice results in schemes based on the hardness of the Ring-LWE and Ring-SIS problems (or the NTRU problem), while the latter choice of parameters results in schemes based on the LWE and SIS problems. In this talk, we consider the general case of setting the ring to (Z_q[x]/(x^d+1))^m, and design schemes based on the Module-LWE and Module-SIS hardness assumption. First, we explain how module lattices enable to design cryptographic primitives that are not only simple to implement securely, conservatively designed, and have a small memory footprint, but are modular, i.e., easily enable to vary security while keeping the same core operations. Then, we present CRYSTALS, the Cryptographic Suite for Algebraic Lattices submitted to the NIST call for post-quantum standards, that includes Kyber (Bos et al., 2017), a key encapsulation mechanism, and Dilithium (Ducas et al., 2017), a digital signature.

LACS Crypto Day, June 13th, 2017, room MSA 4.410, Belval campus