DSD: A Dynamic State-Deflection Method for Gate-Level Netlist Obfuscation

摘要

The emerging security threats in the IC supply chain do not only challenge the chip integrity, but also raise serious concerns on hardware IP piracy and reverse engineering. The existing register-transfer level (RTL) hardware obfuscation methods insert a key sequence in the control and data flow to prevent the attacker from accessing the normal operation mode of a chip, rather than protecting the state transition in the normal operation mode. The lack of protection in the normal operation mode potentially leads the RTL netlist to be vulnerable to register overwrite attack. In this work, we propose to protectall the states with a low-cost state-deflection based obfuscation method, which dynamically deflects the state transition from the original transition path to a black hole cluster. Unlike other work that uses static transitions between legal states to black hole states at the design time, we propose to utilize a state rotation function and selective register flipping function to dynamically control the state deflection paths, thus increasing the difficulty of reverse engineering and thwarting register overwrite attacks. Simulations performed on ISCAS'89 benchmark circuits show that the proposed method significantly reduces the difference of the net toggle activities between the correct and wrong keyscenarios, and achieves up to 56% higher code coverage than other obfuscation methods. Due to the dynamic deflection feature, on average, our method generates 75 more unique state register patterns than the HARPOON method if a wrong key is applied, at the cost of 7.8% power increase.