Improving hardware Trojan detection by retiming

• Effects of path-delays on Trojan testability are studied by analysis and experiment.
• A retiming algorithm, namely TDR, is proposed to enhance Trojan-detection probability.
• TDR works by reducing the process noise during path-delay fingerprinting.
• Trojan detectability is highly improved (up to about 100% if false-alarm rate = 2%).

Hardware Trojan horses (HTHs) are challenging threats to the security of silicon chips. A promising solution is path-delay fingerprinting for HTH detection. This paper presents trust-driven retiming  (TDR)(TDR), a synthesis approach to provide a circuit which can be analyzed more effectively by delay fingerprinting. To this end, TDR tries to reduce the maximum-delay path among all shortest paths crossing each node. We prove that HTH detection probability (HDP) is improved if delay fingerprinting is performed on shorter paths. Experimental results show that TDR can increase the HDP up to more than 90% at the cost of one clock cycle latency and a reasonable area overhead. The HDP tends to 100% if a 2% false alarm rate be acceptable.