COTD: Reference-Free Hardware Trojan Detection and Recovery Based on Controllability and Observability in Gate-Level Netlist

This paper presents a novel hardware Trojan detection technique in gate-level netlist based on the controllability and observability analyses. Using an unsupervised clustering analysis, the paper shows that the controllability and observability characteristics of Trojan gates present significant inter-cluster distance from those of genuine gates in a Trojan-inserted circuit, such that Trojan gates are easily distinguishable. The proposed technique does not require any golden model and can be easily integrated into the current integrated circuit design flow. Furthermore, it performs a static analysis and does not require any test pattern application for Trojan activation either partially or fully. In addition, the timing complexity of the proposed technique is an order of the number of signals in a circuit. Moreover, the proposed technique makes it possible to fully restore an inserted Trojan and to isolate its trigger and payload circuits. The technique has been applied on various types of Trojans, and all Trojans are successfully detected with 0 false positive and negative rates in less than 14 s in the worst case.