Efficient Second-Order Masked KECCAK Implementation without Online Fresh Randomness
: The K ECCAK core is a fundamental cryptographic primitive widely used in post-quantum cryptography to ensure security against emerging quantum-computing attacks. Secure software implementations rely on masking schemes to mitigate side-channel leakage, but these protections introduce significant overhead, which is particularly impactful on resource-constrained microcontrollers and further exacerbated by micro-architectural leakages. To date, publicly available masked K ECCAK implementations do not achieve both efficiency and robustness against such leakages. This work presents an optimized software implementation providing 1 st -order side-channel protection, as well as the first efficiency-oriented 2 nd -order implementation, surpassing previous solutions in performance. Both implementations target the ARM Cortex-M4 microcontroller and satisfy constraints to prevent micro-architectural leakages. A public repository provides the source code and a labeled dataset of 500K+500K traces, enabling reproducibility. Benchmarks show a 44.1% improvement over previously reported first-order implementations.