Trojan detection via delay measurements: A new approach to select paths and vectors to maximize effectiveness and minimize cost

One of the growing issues in IC design is how to establish trustworthiness of chips fabricated by untrusted vendors. Such process, often called Trojan detection, is challenging since the specifics of hardware Trojans inserted by intelligent adversaries are difficult to predict and most Trojans do not affect the logic behavior of the circuit unless they are activated. Also, Trojan detection via parametric measurements becomes increasingly difficult with increasing levels of process variations. In this paper we propose a method that maximizes the resolution of each path delay measurement, in terms of its ability to detect the targeted Trojan. In particular, for each Trojan, our approach accentuates the Trojan´s impact by generating a vector that sensitizes the shortest path passing via the Trojan´s site. We estimate the minimum number of chips to which each vector must be applied to detect the Trojan with sufficient confidence for a given level of process variations. Finally, we demonstrate the significant improvements in effectiveness and cost provided by our approach under high levels of process variations. Experimental results on several benchmark circuits show that we can achieve dramatic reduction in test cost using our approach compared to classical path delay testing.