Transistor-Level Camouflaged Logic Locking Method for Monolithic 3D IC Security

This work proposes a novel method for transistor-level logic locking to address intellectual property (IP) piracy and reverse engineering attacks in monolithic three-dimensional (M3D) ICs. The proposed method locks logic gates by independently inserting parallel or serial locking transistors and camouflaged contacts in multiple tiers in M3D ICs. Without the correct key bits and confidential information for camouflaged contacts, the locked logic gates will malfunction and significantly alter power profiles, which makes reverse engineering attacks more difficult. The performance overhead of the proposed method is evaluated with ISCAS'85 benchmark circuits synthesized and placed with a customized M3D IC library. Case study on c6288 benchmark circuit shows that the proposed locking method with the correct key increases the power by only 0.26%. On average, this method consumes 2.3% more transistors than the baseline ISCAS'85 benchmark circuits.