TLGLock: A New Approach in Logic Locking Using Key-Driven Charge Recycling in Threshold Logic Gates

Abstract: Logic locking remains one of the most promising defenses against hardware piracy, yet current approaches often face challenges in scalability and design overhead. In this paper, we present TLGLock, a new design paradigm that leverages the structural expressiveness of Threshold Logic Gates (TLGs) and the energy efficiency of charge recycling to enforce key-dependent functionality at the gate level. By embedding the key into the gate's weighted logic and utilizing dynamic charge sharing, TLGLock provides a stateless and compact alternative to conventional locking techniques. We implement a complete synthesis-to-locking flow and evaluate it using ISCAS, ITC, and MCNC benchmarks. Results show that TLGLock achieves up to 30% area, 50% delay, and 20% power savings compared to latch-based locking schemes. In comparison with XOR and SFLL-HD methods, TLGLock offers up to 3x higher SAT attack resistance with significantly lower overhead. Furthermore, randomized key-weight experiments demonstrate that TLGLock can reach up to 100% output corruption under incorrect keys, enabling tunable security at minimal cost. These results position TLGLock as a scalable and resilient solution for secure hardware design.