On the Construction of Side-Channel Attack Resilient S-boxes

Side-channel attacks exploit physical characteristics of implementations of cryptographic algorithms in order to extract sensitive information such as the secret key. These physical attacks are among the most powerful attacks against real-world crypto-systems. In recent years, there has been a number of proposals how to increase the resilience of ciphers against side-channel attacks. One class of proposals concentrates on the intrinsic resilience of ciphers and more precisely their S-boxes. A number of properties has been proposed such as the transparency order, the confusion coefficient and the modified transparency order. Although results with those properties confirm that they are (to some extent) related with the S-box resilience, there is still much to be investigated. There, the biggest drawback stems from the fact that even S-boxes with the best possible values of those properties have only slightly improved side-channel resistance. In this paper, we propose to construct small sized S-boxes based on the results of the measurements of the actual physical attacks. More precisely, we model our S-boxes to be as resilient as possible against non-profiled and profiled physical attacks. Our results highlight that we can design 4\times 4 and 5\times 5 S-boxes that possess increased resistance against various real-world attacks.SCOPUS: cp.k