Tancrède Lepoint

applied scientist at AWS

director (2018-2023)
of the IACR

co-editor (since 2016)
of the Cryptology ePrint Archive

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I completed my Ph.D. in June 2014 at École Normale Supérieure of Paris, France with David Pointcheval as advisor, and at University of Luxembourg with Jean-Sébastien Coron as advisor.

My Ph.D. dissertation is entitled Design and Implementation of Lattice-Based Cryptography contains most of my works on lattice-based cryptography, fully homomorphic encryption and multilinear maps.

— my Ph.D. dissertation received the 2014 Gilles Kahn Prize by the Informatics Society of France.

abstract: Today, lattice-based cryptography is a thriving scientific field. Its swift expansion is due, among others, to the attractiveness of fully homomorphic encryption and cryptographic multilinear maps. Lattice-based cryptography has also been recognized for its thrilling properties: a security that can be reduced to worstcase instances of problems over lattices, a quasi-optimal asymptotic efficiency and an alleged resistance to quantum computers. However, its practical use in real-world products leaves a lot to be desired. This thesis accomplishes a step towards this goal by narrowing the gap between theoretical research and practical implementation of recent public key cryptosystems.

In this thesis, we design and implement a lattice-based digital signature, two fully homomorphic encryption schemes and cryptographic multilinear maps. Our highly efficient signature scheme, BLISS, opened the way to implementing lattice-based cryptography on constrained devices and remains as of today a promising primitive for post-quantum cryptography. Our fully homomorphic encryption schemes enjoy competitive homomorphic evaluations of nontrivial circuits. Finally, we describe the first implementation of cryptographic multilinear maps. Based on our implementation, a non interactive key exchange between more than three parties has been realized for the first time, and amounts to a few seconds per party.

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