Unrolling cryptographic circuits: A simple countermeasure against side-channel attacks

Cryptographic cores are used to protect various devices but their physical implementation can be compromised by observing dynamic circuit emanations in order to derive information about the secrets it conceals. Protection against these attacks, also called side channel attacks are major concern of the cryptographic community. Masking and dual-rail precharge logic are promoted as its countermeasures but each has its own vulnerabilities. In this article, we propose a simple countermeasure which comprises unrolling rounds of a cryptographic algorithm such that multiple rounds are executed per clock cycle. This will require a stronger hypothesis on multiple bits due to deeper diffusion of the key. Results show that it resist against correlation power analysis on Hamming distance and Hamming weight model if the datapath is cleared after each operation. We also evaluated mutual information metric on the design and results show that unrolled DES is less vulnerable.