Evaluating the Security of Logic-Locked Probabilistic Circuits
Michael Zuzak, Ankit Mondal, Ankur Srivastava · IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems · 2021
Logic locking is a design-for-security scheme to thwart attacks by an untrusted foundry. Prior work exposed the vulnerability of logic-locked circuits using Boolean satisfiability (SAT). While these attacks are effective against deterministic circuits, they cannot unlock probabilistic/approximate designs, which have become increasingly popular. In this work, we expand SAT-style attacks to locked circuits with a probabilistic behavior. We proposeStatSAT, an attack incorporating statistical techniques into the SAT attack to unlock probabilistic designs. We then propose a countermeasure, called high error rate keys (HERKs), to thwart StatSAT and other attacks on probabilistic circuits. HERKs leverage high error wires, caused by the probabilistic behavior, to hide the correct key under stochastic noise.