Raised Output Corruption and Structural Attack Resilience by Encryption of Big+Little Trees in Logic Locking

Logic locking is an integrated circuit (IC) encryption technique that incorporates key gates and key inputs into a circuit, ensuring correct functionality only when the correct key is applied. Traditional logic locking techniques are vulnerable to the satisfiability (SAT)-based attack method, also known as SAT attack, which decrypts circuits by quickly isolating incorrect keys. Consequently, recent methods employ one-point functions, such as AND-trees, in encrypted circuits to ensure that only one incorrect key is pruned per SAT attack iteration, thereby slowing decryption exponentially. However, these defense methods result in minimal output corruption. Subsequently, solutions like CAS-Lock have emerged, designed to enhance SAT attack resilience and maintain high output corruption, but they remain susceptible to structural attacks. In this work, we introduce the Big+little trees encryption framework to improve output corruption and strengthen resilience against SAT attacks, while effectively concealing structural vulnerabilities to prevent structural attacks. Experimental results show that our method maintains resilience against SAT, Valkyrie, KRATT and FALL attacks while ensuring significant output corruption.