N-MUX: Neighborhood-Based Logic Locking Against Machine Learning Attacks

MUX-based logic locking (LL) is a hardware security technique that inserts multiplexers (MUX) into circuits to secure them against unauthorized use and reverse engineering by protecting original circuit pathways. Nevertheless, MUX-based LL is vulnerable to Oracle-Guided (OG) and Oracle-Less (OL) attacks. While OG methods, such as the SAT attack, are infeasible for large-scale designs, OL attacks, like those based on machine learning (ML), can exploit structural leakage in locked circuits to recover original pathways. This study introduces N-MUX, an innovative MUX-based LL approach designed to resist state-of-the-art (SOTA) ML attacks. N-MUX effectively reduces structural leakage by identifying maximal overlap structures in the original circuit to configure the MUX logic. Additionally, N-MUX ensures high efficiency by selecting the false input from the direct neighbourhood of the true input. Experimental results on ISCAS’85 and ITC’99 benchmarks demonstrate that N-MUX is the most secure and reliable LL technique against SOTA ML-based attacks, achieving an 81% reduction in attack accuracy compared to existing MUX-based LL methods and delivering up to 480× greater efficiency.