Physical Security Evaluation at an Early Design-Phase: A Side-Channel Aware Simulation Methodology

Abstract

Cyber-Physical Systems (CPS) are often deployed in critical domains like health, traffic management etc. Therefore security is one of the major driving factor in development of CPS. In this paper, we focus on cryptographic hardware embedded in CPS and propose a simulation methodology to evaluate the security of these cryptographic hardware cores. Designers are often concerned about attacks like Side-Channel Analysis (SCA) which target the physical implementation of cryptography to compromise its security. SCA considers the physical "leakage" of a well chosen intermediate variable correlated with the secret. Certain countermeasures can be deployed, like dual-rail logic or masking, to resist SCA. However to design an effective countermeasure or to fix the vulnerable sources in a circuit, it is of prime importance for a designer to know the main leaking sources in the device. In practice, security of a circuit is evaluated only after the chip is fabricated followed by a certification process. If the circuit has security concerns, it should pass through all the design phases right from RTL to fabrication which increases time-to-market. In such a scenario, it is very helpful if a designer can determine the vulnerabilities early in the design cycle and fix them. In this paper, we present an evaluation of different strategies to verify the SCA robustness of a cryptographic circuit at different design steps, from the RTL to the final layout. We compare evaluation based on digital and electrical simulations in terms of speed and accuracy in a side-channel context. We show that a low-level digital simulation can be fast and sufficiently accurate for side-channel analysis.