Clockwise Randomization of the Observable Behaviour of Crypto ASICs to Counter Side Channel Attacks

Side channel attacks take advantage from the fact that the behavior of crypto implementations can be observed and provides hints that allow revealing keys. In this paper we present a novel approach to prevent SCA or at least to increase the effort to reveal keys significantly. Our approach is based on the fact that there are some functions used in cryptographic operations that can be implemented using different formulae or algorithms. These algorithms come with their individual complexity that results in individual circuits with individual power consumption. So, if the crypto implementation uses these different algorithms whenever it is executed or if the sequence in which the different algorithms are used is randomized, extracting the key gets extremely challenging if not impossible. Applying our idea is extremely challenging when it comes to ASIC implementations. The point here is that the functionality is fixed and cannot be altered after production. But we discuss that a runtime permutation of the relation between operands and algorithms used for their processing that alters the observable behavior in the same way as executing different algorithms.