Protection against hardware attacks is a fundamental requirement for cryptographic implementations deployed on devices that may be physically accessible to adversaries. The primary threats in such scenarios are SCA and FIA, which are increasingly being combined into potent joint attacks. A prominent example is the SCA-NFA technique, which has been shown to circumvent DOMREP, a countermeasure designed to provide individual protections against both SCA and FIA. In this work, we present DOMREP-II, which extends the original scheme to withstand powerful adversaries with SCA-NFA capabilities. We adapt non-linear DOM gates to ensure strong non-interference under the presence of faults and develop a protected error-correction gate that eliminates secret-dependent leakage during the redundancy-checking phase. The proposed countermeasure is validated using first-order TVLA and a detailed empirical SCA-NFA analysis on a microcontroller platform. Our results demonstrate that while the original Domain Oriented Masking with REPetiton codes (DOMREP) implementation leaks the secret key within 100,000 traces, DOMREP-II successfully mitigates this leakage. When applied to the Gimli permutation, the enhanced protection introduces a moderate performance overhead of 18.8% in cycle count and only 4.4% in code size. Furthermore, we show that the authenticated structure of our countermeasure enables secure randomness reuse, reducing the entropy demand to 696 bytes per permutation. These findings confirm that DOMREP-II provides a practical and scalable security-performance trade-off for high-assurance cryptographic implementations.
Probst et al. (Tue,) studied this question.