New design strategy for improving hardware Trojan detection and reducing Trojan activation time

Hardware Trojans in integrated circuits and systems have become serious concern to fabless semiconductor industry and government agencies in recent years. Most of the previously proposed Trojan detection methods rely on Trojan activation to either observe a faulty output or measure side-channel signals such as transient current or charge. From the authentication stand point, time to trigger a hardware Trojan circuit is a a major concern. This paper analyzes time to (i) generate a transition in functional Trojans and (ii) fully activate them. An efficient dummy flip-flop insertion procedure is proposed to increase Trojan activity. Depending on authentication time and circuit topology, a transition probability threshold is selected so that inserted dummy flip-flops would moderately impact area overhead. The simulation results on s38417 benchmark circuit demonstrate that, with a negligible area overhead, our proposed method can significantly increase Trojan activity and reduce Trojan activation time.