November 29, 2022
Melissa Azouaoui - NXP Semiconductors
CRYSTALS-Dilithium has been selected by the NIST as the new standard for post-quantum digital signatures. In this work, we revisit the side-channel countermeasures of Dilithium in three directions. First, we improve its sensitivity analysis by classifying intermediate computations according their physical security requirements. This allows us to identify which parts of Dilithium must be protected against Differential Power Analysis (DPA), which parts must be protected against Simple Power Analysis (SPA) and which parts can leak in an unbounded manner. Second, we provide improved gadgets dedicated to Dilithium, taking advantage of recent advances in masking conversion algorithms. Third, we combine these contributions with standard shuffling techniques in order to design so-called leveled implementations that offer an improved security vs. performance trade-off compared to the state-of-the-art. Our benchmarking results additionally put forward that the randomized version of Dilithium can lead to significantly more efficient implementations (than its deterministic version) when side-channel attacks are a concern.