Study of Hardware Trojans in a Closed Loop Control System for an Internet-of-Things Application

A closed-loop system is a primary technology used to automate our critical infrastructure and major industries to improve their efficiency. Their dependability is challenged by probable vulnerabilities in the core computing system. These vulnerabilities can appear on both front (software) and back (hardware) ends of the computing system. While the software vulnerabilities are well researched and documented, the hardware ones are normally overlooked. However, with hardware-inclusive technological evolutions like Cyber-Physical Systems and Internet-of-Things, hardware vulnerabilities should be addressed appropriately. In this work, we present a study of one such vulnerability, called Hardware Trojan (HT), on a closed-loop control system. Since a typical hardware Trojan is a small and stealthy digital circuit, we present a test platform built using FPGA-in-the-loop, where the computing system is represented as a digital hardware. Through this platform, a comprehensive runtime analysis of hardware Trojan is accomplished and we developed four threat models that can lead to destabilization of the closed-loop system causing hazardous conditions. Since the primary objective is to study the effects of hardware Trojans, they are designed in such a way that they can be accessible and controllable.