Automated Trigger Activation by Repeated Maximal Clique Sampling

Abstract

Hardware Trojans are serious threat to security and reliability of computing systems. It is hard to detect these malicious implants using traditional validation methods since an adversary is likely to hide them under rare trigger conditions. While existing statistical test generation methods are promising for Trojan detection, they are not suitable for activating extremely rare trigger conditions in stealthy Trojans. To address the fundamental challenge of activating rare triggers, we propose a new test generation paradigm by mapping trigger activation problem to clique cover problem. The basic idea is to utilize a satisfiability solver to construct a test corresponding to each maximal clique. This paper makes two fundamental contributions: 1) it proves that the trigger activation problem can be mapped to clique cover problem, 2) it proposes an efficient test generation algorithm to activate trigger conditions by repeated maximal clique sampling. Experimental results demonstrate that our approach is scalable and it outperforms state-of-the-art approaches by several orders-of-magnitude in detecting stealthy Trojans.