Low Overhead System-Level Obfuscation through Hardware Resource Sharing

Abstract

Logic locking techniques have been proposed to protect chip designs from malicious reverse engineering and overproduction. Stripped functionality logic locking (SFLL) has gained substantial traction as a current state of the art method, exhibiting strong resilience against a wide variety of attacks. However, secure instances of SFLL-based locking tend to have high power and area overheads, particularly in its restore units. This work presents a novel architectural approach to restore unit configuration for SFLL-like logic locking methods that treats restore units as an overhead-constrained shareable resource. We describe how resource contention caused by sharing of restore units imposes constraints on the underlying locking scheme from a graph theoretic perspective and propose both a 0-1 ILP and a heuristic clustering algorithm for finding resource-constrained shared locking configurations that satisfy these constraints. We evaluate our sharing method on SFLL-flex and find that our ILP and heuristic methods were each able to achieve a 55% and 31% reduction in power used by locked datapaths synthesized from MediaBench benchmarks while maintaining the same security and functionality compared to datapaths locked with conventional gate-level techniques.