Attacking and Securing the Clock Randomization and Duplication Side-Channel Attack Countermeasure

The emergence of deep learning has revolutionized side-channel attacks, making them a serious threat to cryptographic systems. Clock randomization is a well-established mitigation technique against side-channel attacks that, when combined with duplication, has been shown to effectively protect FPGA implementations of block ciphers and post-quantum KEMs. In this paper, we present two deep-learning-based side-channel attacks on an FPGA implementation of AES protected with the clock randomization and duplication countermeasure. The attacks are based on identifying sporadic synchronicity in the execution of the encryption rounds of the two AES cores. We remedy this vulnerability by presenting three modular additions to the original design of the countermeasure that restores its security and increases its robustness.