Revisit fault sensitivity analysis on WDDL-AES

This paper revisits and improves the fault sensitivity analysis (FSA) attack on WDDL-AES. At CHES 2010, the FSA attack on WDDL-AES was proposed by Li et al. based on the delay timing difference for complementary wires. In their attack, the vulnerability of WDDL-AES mainly comes from the implementation deficiency rather than the WDDL technique itself. On the contrary, we explain that a well-implemented WDDL-AES also has the vulnerability against the FSA attack due to the input-data dependency for the critical delay of the WDDL S-box. We explain the observed ciphertext-bit dependency for the fault sensitivity (FS) data when the clock glitch is injected at the final AES round. By proposing a new distinguisher, our FSA attack can successfully retrieve the secret key information for WDDL-AES on SASEBO-R.