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Masked Computation of the Floor Function and Its Application to the FALCON Signature
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| Abstract: | FALCON is a signature selected for standardisation of the new Post-Quantum Cryptography (PQC) primitives by the National Institute of Standards and Technology (NIST). However, it remains a challenge to define efficient countermeasures against side-channel attacks (SCA) for this algorithm. FALCON is a lattice-based signature that relies on rational numbers, which is unusual in the cryptography field. Although recent work proposed a solution to mask the addition and the multiplication, some roadblocks remain, most noticeably, how to protect the floor function. In this work, we propose to complete the first existing tests of hardening FALCON against SCA. We perform the mathematical proofs of our methods as well as formal security proofs in the probing model by ensuring Multiple Input Multiple Output Strong Non-Interference (MIMO-SNI) security. We provide performances on a laptop computer of our gadgets as well as of a complete masked FALCON. We notice significant overhead in doing so and discuss the deployability of our method in a real-world context. |
BibTeX
@article{cic-2025-34902,
title={Masked Computation of the Floor Function and Its Application to the FALCON Signature},
journal={cic},
publisher={International Association for Cryptologic Research},
volume={1, Issue 4},
url={https://cic.iacr.org/p/1/4/9},
doi={10.62056/ay73zl7s},
author={Pierre-Augustin Berthet and Justine Paillet and Cédric Tavernier and Lilian Bossuet and Brice Colombier},
year=2025
}