SCONE: A Logic Locking Technique Utilizing SMT Solver and Circuit Encoding Scheme for Efficient Hardware IP Protection
Zhaokun Han, Daniel Xing, Kostas Amberiadis, Ankur Srivastava, Jeyavijayan Rajendran · 2025
Multiple intellectual property (IP) protections have emerged to defeat security threats in integrated circuit (IC) supply chain. Among these, logic locking is regarded as a promising IP protection for its security. A state-of-the-art work uses stripped-functionality logic locking (SFLL) technique with protected input patterns (PIPs) satisfying the distance of at least 2 (Dist2) property, or D2PIPs, for ensuring resilience against both input-output (I/O)-based and structural attacks. However, this approach has research challenges in scalability, flexibility, and security, as stated and discussed in our paper. Our paper solves these challenges by (i) utilizing a satisfiability modulo theories (SMT) solver and (ii) developing a secure circuit encoding scheme. SCONE, our secure logic locking technique, combines the two methods and meets all three challenges simultaneously. Our results show that SCONE improves scalability $\mathbf{3 5 0} \times$ on the IBEX processor (16 K gates) and remains resilient against five I/O or structural attacks. Index Terms-logic locking, encoding scheme, SMT solver.