Paper 2019/478

BEARZ Attack FALCON: Implementation Attacks with Countermeasures on the FALCON signature scheme

Sarah McCarthy, James Howe, Neil Smyth, Seamus Brannigan, and Máire O’Neill

Abstract

Post-quantum cryptography is an important and growing area of research due to the threat of quantum computers, as recognised by the National Institute of Standards and Technology (NIST) recent call for standardisation. Lattice-based signatures have been shown in the past to be susceptible to side-channel attacks. Falcon is a lattice-based signature candidate submitted to NIST, which has good performance but lacks in research with respect to implementation attacks and resistance. This research proposes the first fault attack analysis on Falcon and finds its lattice trapdoor sampler is as vulnerable to fault attacks as the GPV sampler used in alternative signature schemes. We simulate the post-processing component of this fault attack and achieve a 100% success rate at retrieving the private-key. This research then proposes an evaluation of countermeasures to prevent this fault attack and timing attacks on Falcon. We provide cost evaluations on the overheads of the proposed countermeasures which shows that Falcon has only up to 30% deterioration in performance of its key generation, and only 5% in its signing, compared to without countermeasures.