HardObfSec: Measuring Hardware Obfuscation Security at RTL

¹Abstract-In the face of growing threats from Reverse Engineering (RE) attacks, protecting Integrated Circuit (IC) designs has become paramount. Hardware obfuscation stands out as a powerful defense mechanism by deliberately modifying a circuit’s functional behavior, making it significantly more challenging for adversaries to extract its true functionality. A key aspect of obfuscation effectiveness lies in its ability to generate multiple functional variations, among which only one is correct, while the others mislead attackers. Despite its significance, traditional evaluation metrics often fail to capture the full extent of obfuscation effectiveness, as they overlook key aspects such as complexity, and ambiguity introduced by generating misleading functionalities. This limitation hinders accurate assessment of how well an obfuscation technique increases circuit complexity, and prevents adversaries from extracting meaningful design information. To address this gap, this paper introduces HardObfSec, a novel metric for holistic assessment of obfuscation robustness. HardObfSec evaluates the applied obfuscation attributes, and their impact on the circuit’s structural attributes. By quantifying data, and operation obscurity, it measures the complexity, and ambiguity introduced by obfuscation, and determines how many distinct functionalities an obfuscated design can generate. This metric offers a precise, and reliable measure of the resilience of obfuscated designs against RE attacks.