Last-Round and Joint First/Last-Round Power Analysis Attacks on PRESENT

This paper explores new power analysis attacks on cryptographic circuits based on the PRESENT cipher, and discloses an unreported vulnerability of this cipher. For the first time, an attack to the last round is introduced to identify the secret key based on the knowledge of ciphertext, as opposed to conventional attacks based on the first round (i.e., knowledge of plaintext). This attack is enabled by the analysis of the bit-permutation structure in the last round, and by introducing a suitable bit regrouping strategy. As further contribution, a more powerful attack combining first/last-round Correlation Power Analysis attacks with Top-N guess strategy is demonstrated. The analysis and the attack results show that the optimal choice of Top-N key guesses makes the proposed attack more powerful than a conventional single-round attack, reducing the number of power traces required by 34%.