Mélissa Rossi – Assessing residual security of lattice-based cryptography

This talk will present a framework for cryptanalysis of lattice-based schemes, when side information —in the form of «hints»— about the secret is available. This presentation outlines a joint work with Dana Dachman-Soled, Léo Ducas and Huijing Gong that was presented in CRYPTO 2020 (EPrint on IACR).

This framework generalizes the primal lattice reduction attack, and allows the progressive integration of hints before running a final lattice reduction step. The techniques for integrating hints include sparsifying the lattice, projecting onto and intersecting with hyperplanes, and/or altering the distribution of the secret vector. The main contribution is to propose a toolbox and a methodology to integrate such hints into lattice reduction attacks and to predict the performance of those lattice attacks with side information.

While initially designed for side-channel information, this framework can also be used in other cases. For example, one can simply exploit constraints imposed by certain schemes (LAC, Round5, NTRU). Besides, I will present a way to use this framework combined with decryption failures information using a joint work with Jan-Pieter D’Anvers and Fernando Virdia presented in EUROCRYPT 2020 (EPrint on IACR).

https://webconference.unicaen.fr/b/mor-7jm-rcy