Design of a duplicated fault - detecting AES chip and yet using clock set - up time violations to extract 13 out of 16 bytes of the secret key .

1 Introduction The secret keys manipulated by cryptographic circuits can be extracted using fault injections associated with differential cryptanalysis techniques [1]. Such faults can be induced by different means such as lasers, voltage glitches, electromagnetic perturbations or clock skews. Several countermeasures have been proposed such as random delay insertions, circuit duplications or error correcting codes. In this paper, we focus on an AES chip in which the circuit duplication principle has been implemented to detect fault injection. We show that faults based on clock setup time violations can nevertheless be used to defeat the implemented countermeasure .