Paper 2025/171

A light white-box masking scheme using Dummy Shuffled Secure Multiplication

Abstract

In white-box cryptography, early encoding-based countermeasures have been broken by the DCA attack, leading to the utilization of masking schemes against a surge of automated attacks. The recent filtering attack from CHES 2024 broke the last viable masking scheme from CHES 2021 resisting both computational and algebraic attacks, raising the need for new countermeasures. In this work, we perform the first formal study of the combinations of existing countermeasures and demonstrate that applying Dummy Shuffling (EUROCRYPT 2021) then ISW masking (CRYPTO 2003) to a circuit carries algebraic, correlation, and filtering security - necessary conditions to withstand state-of-the-art automated attacks. We also show that applying these two countermeasures in the opposite order leads to a Higher-Order Filtering attack, highlighting the importance of the order of application of the combined countermeasures. We also propose a new masking scheme called S5, standing for the Semi-Shuffled Secret Sharing Scheme, a scheme merging Dummy Shuffling and ISW in a single countermeasure more efficiently than a direct composition.