[Resource Topic] 2025/628: Improving the Masked Division for the FALCON Signature

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Title:
Improving the Masked Division for the FALCON Signature

Authors: Pierre-Augustin Berthet, Justine Paillet, Cédric Tavernier, Lilian Bossuet, Brice Colombier

Abstract:

FALCON is a post-quantum signature selected by the National Institute of Standards and Technology (NIST). Although its side-channel resilience has been studied and a masking countermeasure proposed, the division is a major performance bottleneck. This work proposes a different approach to the masked FALCON division. We use the Newton method and a convergent sequence to approximate this operation. The performance of the masked division is improved by a factor 6.7 for two shares and 6.98 for three shares. For the Gaussian sampler, the improvements are of a factor 1.45 for two shares and 1.43 for three shares. Formal security proofs using the MIMO-SNI criteria are also provided.

ePrint: https://eprint.iacr.org/2025/628

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