A Demonstration of a HT-Detection Method Based on Impedance Measurements of the Wiring Around ICs

Threats that cause malicious function such as information leakage and denial of service by adding hardware trojan (HT) to a device constructed using inexpensive elements at component level after shipment have been reported. The detection method after shipment, which is different from HT detection inside IC is required because of the easiness adding component-level HT to products. The testing method to detect modification on board will achieve the detection of component-level HT. In this brief, we focus on the HT implemented in the wiring connected to integrated circuits. Since the component connection constantly affects the impedance of the wiring, we propose a detection method for such HT implemented outside the IC by measuring the change in the impedance of the wiring. For the detection of malicious modification after shipment it is necessary to excite a pulse signal from the IC that achieves high security, such as a secure microcomputer, and observe the signal reflected inside the secure IC by the discontinuous portion of the impedance on the board. If the reflected signal is different from the shipping test, it can be judged that HT is mounted. We adopted time domain reflectometry (TDR) to realize the above method, and we demonstrate experimental result of component-level HT detection using TDR with measuring instrument and TDR from secure IC. As a result, a significant change in the amplitude due to the impedance change was obtained from the reflected wave measured inside the IC with and without the MOSFET used as the HT using this method.