Differential Fault Attacks against AES Tampering with the Instruction Flow

Most of the attacks against the Advanced Encryption Standard based on faults mainly aim at either altering the temporary value of the message or key during the computation. Few other attacks tamper the instruction flow in order to reduce the number of round iterations to one or two. In this work, we extend this idea and present fault attacks against the AES algorithm that exploit the misbehavior of the instruction flow during the last round. In particular, we consider faults that cause the algorithm to skip, repeat or corrupt one of the four AES round functions. In principle, these attacks are applicable against both software and hardware implementations, by targeting the execution of instructions or the control logic. As conclusion countermeasures against fault attacks must also cover the instruction flow and not only the processed data.