High Resolution Pulse Propagation Driven Trojan Detection in Digital Systems

Outsourcing of IC manufacturing has opened the possibility of intentionally modifying the operation of the IC in a subtle way so that it is extremely difficult to detect, in conventional functional testing. Security in computation is no longer a software only issue, the underlying computing hardware may also be compromised. As occurrence of Trojan activation is rare event, it needs to be detected without actually activating it. In digital systems Trojan payload takes input from low activity nodes of the original circuit. Even when the Trojan is not activated, these tapings of original circuit nodes exhibit extra capacitive load. This work is geared towards detecting these extra capacitances with unprecedented accuracy to uncover malicious Trojans in the circuit. We have shown that pulse propagation in logic circuit can be used to detect any extra stray capacitance at any circuit node with 20-25X better diagnostic resolution than that of any other delay and frequency measurement based techniques. We have developed a current sensor that monitors supply currents at predetermined low activity gates. If any one of these nodes are tapped for Trojan, then due to extra capacitive load the applied pulse gets killed and the difference maximum current (before and after pulse) indicate Trojan occurrence. While majority of the Trojan detection techniques loose diagnostic accuracy with the size of the circuit and amount of process variation, diagnostic capability of the proposed pulse based technique is independent of size of the circuit. The proposed scheme can be integrated into JTAG boundary scan to provide a complete solution for hardware Trojan detection in digital systems.