An Extension of Fault Sensitivity Analysis Based on Clockwise Collision

This paper proposes an extension of fault sensitivity analysis based on

clockwise collision

. The original FSA attack uses the fault injections to exploit the sensitivity of calculations against the fault injections. While the clockwise collision fault sensitivity analysis (CC-FSA) uses the fault injections to detect the occurrence of the clockwise collision and to recover the secret key. Clockwise collision is a phenomenon for iterative hardware circuits, which leads to nearly impossible setup-time violations. Take an AES S-box as an instance, clockwise collision occurs when the S-box inputs for two consecutive clock cycles are identical in value. As a result, the combinational circuit in the second clock cycle has almost no signal toggle and a negligible critical path delay. This paper proposes and verifies the concept of CC-FSA using the clock-glitch-based fault injections and an unprotected AES implementation. We investigate the key recovery method for CC-FSA with a noisy data set and we consider CC-FSA can help the previous collision-based model-less FSA attack to identify the final 8-bit secret information without additional data and negligible computational overhead.