Attacking and Defending Masked Polynomial Comparison for Lattice-Based Cryptography

In this work, we are concerned with the hardening of post-quantum key encapsulation mechanisms (KEM) against side-channel attacks, a focus on comparison operation required for Fujisaki-Okamoto (FO) transform. We identify critical vulnerabilities in two proposals masked and successfully attack algorithms from TCHES 2018 2020. To do so, use first-order attacks show that advertised security properties not hold. Additionally, break higher-order secured 2020 using collision attack, which does require information. enable implementers to spot such flaws implementation or underlying algorithms, propose framework is designed test re-encryption step FO transform information leakage. Our relies specifically parametrized t-test would have identified previously mentioned comparison. can be used both itself full decapsulation implementation.