A Generic Method for Secure SBox Implementation

Cryptographic algorithms embedded in low resource devices are vulnerable to side channel attacks. Since their introduction in 1996, the effectiveness of these attacks has been highly improved and many countermeasures have been invalidated. It was especially true for countermeasures whose security was based on heuristics and experiments. Consequently, there is not only a need for designing new and various countermeasures, but it is also necessary to prove the security of the new proposals in formal models. In this paper we provide a simple method for securing the software implementation of functions called SBoxes that are widely used in symmetric cryptosystems. The main advantage of the proposed solution is that it does not require any RAM allocation. We analyze its efficiency and we compare it with other well-known countermeasures. Moreover, we use a recently introduced proof-of-security framework to demonstrate the resistance of our countermeasure from the viewpoint of Differential Power Analysis. Finally, we apply our method to protect the AES implementation and we show that the performances are suitable for practical implementations.