Paper 2025/1936 Original: eprint.iacr.org/2025/1936 ↗

Overshooting the Threshold: ($td+n$)-Masking

Abstract

Masking is one of the most widespread countermeasures against side-channel attacks. However, its integration into hardware implementation is subject to physical hazards that can mitigate its security. To counter glitches, the most studied physical hazard, an effective solution is to resynchronize the signals by integrating additional hardware layers into the architecture. However, these solutions have an impact on the performance of the implementation. A solution to avoid these limitations is to use more shares to compute higher-degree functions. We study the cost of this approach, denominated ($td+n$)-masking. We first derive optimal dependence structures for the creation on non-complete sharings, which allow us to obtain efficient implementation of substitution boxes. As a case study, we use these elements to create a second-order masked architecture for the PRESENT cipher. We perform multiple TVLA tests to validate our approach. Our results confirm that the strategy is efficient in terms of performance, at the cost of increased hardware resources.