Rethinking IC Layout Vulnerability: Simulation-Based Hardware Trojan Threat Assessment with High Fidelity

Due to the escalating complexity of chip design and the exorbitant cost of building cutting-edge manufacturing facilities, outsourcing the fabrication of Integrated Circuits (ICs) is prevalent in modern semiconductor industry. However, significant security risks may arise because untrustworthy foundries can conduct insidious attacks without close supervision. Since prior works show the feasibility of implementing practical foundry-level Trojan attacks that circumvent post-fabrication detection, IC designers should protect their IC layouts before sending them to a third-party foundry, and such protections are known as design-time defenses. To this end, security metrics for layout vulnerability assessment are crucial to test the effectiveness of the proposed defenses. However, existing metrics are geometric-only and Trojan-oblivious, failing to capture the fundamental aspects of foundry-level Trojan insertion and the associated side effects.To bridge the gap between real attacks and threat prediction, we present SiliconCritic, a simulation-based, extensible framework that leverages design-time techniques to simulate the blackbox foundry-level Trojan attacks and post-fabrication analysis. SiliconCritic encodes the difficulty of inserting a specific Trojan into a finalized physical layout by measuring the variation of side-channel parameters (timing, power) after the simulated Trojan insertion, where larger deviations denote better detectability and thus enhanced security. SiliconCritic allows IC designers to interactively refine defensive strategies against the objective Trojan based on the feedback of side-channel analysis. Through evaluations on real-world ASIC designs and reported hardware Trojans, SiliconCritic demonstrates the limitations of existing layout-level defenses and highlights the influence of Trojan properties on defensive efficacy. Our work refreshes the understanding of Trojan prevention and suggests future directions for defenses against untrustworthy foundries.