Board-Level Hardware Trojan Detection Using on-Chip Touch Sensor

Abstract

There have been reports of threats that cause electromagnetic information leakage by inserting Hardware Trojans (HT) into the signal traces around components on the printed circuit board (PCB). In this threat, the HT insertion is assumed not only at the manufacturing stage but also during the in-transit or in the field after shipment, and the threat may extend to devices that are not considered to be threatened by HT insertion implemented inside conventional ICs. This paper discusses the detection method for the HT insertion, which is implementable on a PCB without external measurement equipment. Additionally, we validate the method in more practical situations, detecting the HT on populated PCBs. The method employs an on-chip touch sensor to measure the changes in electrical characteristics caused by HT insertion. Specifically, HT insertion is detected by observing the change in capacitance and insulation resistance associated with HT insertion using the on-chip sensor, and detecting the difference from the measurement result when HT is not inserted to signal traces. In the experiment, we build an evaluation environment, which emulates a populated PCB, based on the HT insertion method reported in previous studies and observe the change in capacitance and insulation resistance on the connected signal trace using a microprocessor equipped with a constant current source and an analog-digital converter that constitute the on-chip sensor. Then, we show that HT insertion on the signal trace can be detected from the output values of the on-chip sensor before and after HT insertion.