Functional Reverse Engineering on SAT-Attack Resilient Logic Locking

Logic locking is a solution that mitigates hardware security threats, such as Trojan insertion, piracy and counterfeiting. Research in this area has led to, in an iterative fashion, a series of logic locking defenses as well as attacks that circumvent these defenses by extracting the logic locking key. The most powerful attacks rely on a full access to a working chip/oracle that can be used to produce the input-output pairs utilized in recovering the secret key. A recently proposed technique Stripped Functionality Logic Locking (SFLL) provides resilience to all known attacks on combinational logic locking. In this paper, we propose a functional reverse engineering attack on SFLL: an attack that can detect the protection logic of SFLL which results in obtaining the original unlocked design with a high success rate. The restore and perturb blocks utilized by SFLL were detected with average coverage percentages of 93.95% and 85.42% respectively, proving that our attack is capable of breaking the state of the art logic locking technique.