Research On Logic Locking With Structural Interference

Logic locking technology is a new chip information protection technology for reverse engineering and IC overproduction caused by untrusted factories.Since SAT solver was applied in logic locking cracking,ordinary encryption methods could not provide sufficient security.To resist SAT attack,point function-based cryptography has been proposed,in which Stripped-Functionality Logic Locking(SFLL)cryptography provides strong resistance to SAT while maintaining security against approximate attacks and removal attacks.However,with the latest Valkyrie structure attack was proposed,all the previous 15 combinatorial logic locking encryption techniques were broken in a short time.In this thesis,we propose Structural Interference Logic Locking(SILL),which firstly obfuscates the common encryption structure features by combining the added interference logic with the traditional encryption logic to jointly drive the encryption signals,and allocates the keys to the encryption logic and interference logic according to fixed rules to achieve the defense against Valkyrie structure attack.SILL cryptography can secondly combine all the previous cryptographic techniques to jointly resist Valkyrie attack,while inheriting the anti-attack performance of previous cryptographic techniques.SILL cryptography can again filter the key assignment strategy with the strongest resistance to SAT attack through theoretical analysis to achieve maximum resistance and minimum encryption overhead against SAT attack.The SILL encryption technique finally increases the complexity of solving the Valkyrie structure attack by studying the effects of encryption location,number of keys and number of protected outputs on the number of candidate critical signals screened by the Valkyrie structure attack.Theoretical analysis and experiments show that the SAT resistance of SILL encryption circuit is between(k-4)and(k-2),which is lower than(k-1)which is the SAT resistance of SFLL-HD.Although the SAT resistance of the SILL encryption circuit is1/8 to 1/2 of the SFLL-HD resistance,the actual cracking time of the SILL encryption circuit is at least 124 times longer than the cracking time of the SFLL-HD due to the complete resistance to the Valkyrie attack that the SILL encryption circuit has.