Evaluating coherence-exploiting hardware Trojan

Increasing complexity of integrated circuits and IP-based hardware designs have created the risk of hardware Trojans. This paper introduces a new type of threat, a coherence-exploiting hardware Trojan. This Trojan can be maliciously implanted in master components in a system, and continuously injects memory transactions onto the main interconnect. The injected traffic forces the eviction of cache lines, taking advantage of cache coherence protocols. This type of Trojans insidiously slows down the system performance, incurring Denial-of-Service (DoS) attack. We used a Xilinx Zynq-7000 device to implement the Trojan and evaluate its severity. Experiments revealed that the system performance can be severely degraded as much as 258% with the Trojan. A countermeasure to annihilate the Trojan attack is proposed in detail. We also found that AXI version 3.0 supports a seemingly irrelevant invalidation protocol through ACP, opening a door for the potential Trojan attack.