SPARX — A side-channel protected processor for ARX-based cryptography

ARX-based cryptographic algorithms are composed of only three elemental operations — addition, rotation and exclusive or — which are mixed to ensure adequate confusion and diffusion properties. While ARX-ciphers can easily be protected against timing attacks, special measures like masking have to be taken in order to prevent power and electromagnetic analysis. In this paper we present a processor architecture for ARX-based cryptography, that intrinsically guarantees first-order SCA resistance of any implemented algorithm. This is achieved by protecting the complete data path using a Boolean masking scheme with three shares. We evaluate our security claims by mapping an ARX-algorithm to the proposed architecture and using the common leakage detection methodology based on Student's i-test to certify the side-channel resistance of our processor.