A Hardware Trojan Exploiting Coherence Protocol on NoCs

Intellectual property (IP) has been used in Network on chips (NoCs) for reducing costs and shortening the time to market. However, there is a probability that a third-party vendor injects hardware that behaves maliciously. This study firstly illustrates the security risk of a hardware Trojan for eavesdropping and reducing the system performance by malicious coherent messages. It only increases the amounts of communications and calculations obeying a coherence protocol, allowing applications to perform correctly. This study secondly presents its countermeasure at network interfaces. It compares the number of output messages to input messages at network interfaces to detect malicious coherent messages. This risk causes, on a chip-multiprocessor, execution time to increase by up to 24%, the amount of traffic to increase by up to 18%, and the energy consumption to increase by up to 8.9%. Since the benchmarks in the evaluation are small, we expect that real-life applications would be highly affected by the hardware Trojan. Our countermeasure avoids these performance degradation, and it can be implemented with a significantly low overhead of only 1.3% in a network interface on a chip.