Frontside laser fault injection on cryptosystems - Application to the AES´ last round -

Laser fault injection through the front side (and consequently the metal-flls) of an IC is often performed with medium or small laser beams for the purpose of injecting bytewise faults. We have investigated in this paper the properties of fault injection with a larger laser beam (in the 100/im range). We have also checked whether the bit-set (or bit-reset) fault type still holds or whether the bit-fip fault type may be encountered. Laser injection experiments were performed during the last round of the Advanced Encryption Standard (AES) algorithm running on an ASIC. The gathered data allowed to investigate the obtained fault models, to conduct two usual Differencial Fault Attack (DFA) schemes and to propose a simple version of a third DFA.