Replacement-Based Key-Controlled Circuits: A New Lightweight Logic-Locking Technique to Prevent the SAT Attack and Its Variants

The current trend of globalization of the supply chain in the integrated circuit (IC) industry has led to numerous security issues, such as intellectual property (IP) piracy, overbuilding, hardware Trojan (HT), and so on. Over the past decade or so, logic locking has been developed as an important method to prevent or mitigate the above security issues in ICs throughout their lifecycles. However, most published logic locking schemes are vulnerable to the SAT attack and its variants. Existing SAT-resilient locking schemes always entail a trade-off between security and effectiveness and incur significant hardware overhead. In this paper, we propose a new replacement-based key-controlled circuit (called RKC), the application of which changes the underlying framework of traditional logic locking designs, making the SAT attack and its variants infeasible in the framework. To achieve stronger functional and structural obfuscation and to validate the extensibility of the proposed method within the modified logic-locking design framework, we develop a new multi-input key-controlled circuit (called MKC) via vertical extension, also based on replacement applied to the locking design. In addition, we expand the two proposed circuits horizontally by varying the design parameter m, yielding four logic-locking design circuits. Relevant experiments performed on six selected benchmark circuits from ISCAS’85 and MCNC benchmarks show that the proposed method demonstrates superior/less hardware overhead compared to four recently published locking methods, i.e., GateLock, SKG-Lock, SKG-Lock+, and CAS-Lock.