Enhancing security in QCA-based circuits using optimal key gate placement

Quantum-dot Cellular Automata (QCA) is an emerging nanotechnology that explores the potential of using quantum effects to build compact and energy-efficient computational devices. The hardware attacks on QCA primarily target understanding the physical structure and operation of these nanotechnological circuits. The circuits like cryptographic processors hold sensitive data that needs protection from third-party attacks. Logic locking is a hardware protection technique that adds additional gates to the original circuits to prevent circuits from these attacks. In this work, a new logic locking approach is proposed for QCA based circuits. The new configurable logic gate or key gate is introduced for logic locking. This gate can be configured to either wire or inverter based on key gate inputs. Further, the metaheuristic optimization based optimal key gate placement algorithm proposed to achieve higher security with minimum key gate placement. The proposed approach is verified in QCA benchmark circuits using QCA-Designer. Results shows that the proposed achieves maximum security with minimal gate replacements.