A Security Comparison between AES-128 and AES-256 FPGA implementations against DPA attacks

As the AES is the standard symmetric cipher selected by NIST, is the best-known and the most widely used block cipher. Consequently, security threats are constantly rising and increasingly powerful. With the addition of the upcoming scenario of quantum computing, these threats have become a front-line concern in the crypto-community. Although is claimed that using larger key sizes in symmetric key algorithms for implementing quantum-resistant implementations is enough to counteract brute force attacks, this paper shows that both AES128 and AES-256 are vulnerable to Power Analysis attacks. This paper presents a security comparison against Differential Power Analysis (DPA) attacks over both AES 128-256. Through experimental attacks in FPGA AES implementations, results show that although AES-256 reaches a greater level of security than AES128, is still vulnerable to this kind of attack. Specifically, we have obtained 75% of the bytes needed to find the original key for AES-128 while only 28.125% for AES-256 by performing the same attack.