Countering early evaluation: an approach towards robust dual-rail precharge logic

Abstract

Wave Dynamic Differential Logic (WDDL) is a hiding countermeasure to thrawt side channel attacks (SCA). It suffers from a vulnerability called Early Evaluation, i.e. calculating output before all inputs are valid. This causes delay biases in WDDL even when synthesized with positive gates. s a consequence, the design can be attacked, although with extra effort, through side channel. However, WDDL is an appealing logic since it has already been reported to natively resist against multiple asymmetric faults. In this article, we suggest a Dual Rail Precharge Logic (DPL), similar to WDDL, free from early evaluation by design. We demonstrate practically that the early evaluation accounts for major part of the leakage. We also provide basic guidelines for designing such a DPL. This DPL can resist against side channel attacks and fault attacks at the same time. In line with the current security evaluation methodology, we use differential power analysis and mutual information to compare the modified WDDL with the traditional WDDL. To compare robustness w.r.t security, we conduct a proof-of-concept experiment that compares the two logics with identical implementations (P&R) apart from the logic style. The sensitive side channel leakage is reduced by half in the DPL without the early evaluation flaw.