The invention relates to a logic 
encryption defense method based on key gate position selection. The method mainly comprises two parts: data preprocessing and a key gate position 
encryption algorithm.Specifically, in the 
encryption process, the positions of the secret key 
doors are marked in a data preprocessing mode, paths with too long 
delay are removed, and then a two-stage encryption 
algorithm is adopted for implanting the positions of the secret key 
doors and a main guide door. Finally, the 
Hamming distance and an area overhead are calculated to evaluate the security standard of the encrypted circuit. According to the method, the gate-level 
netlist encryption effect can be improved; the 
Hamming distance is greater than 50% through a dominant gate implantation 
algorithm; the output 
ambiguity is maximized, the security protection circuit is simple in structure, can 
resist secret key 
sensitization attacks, simultaneously reduces area overhead, comprehensively improves security evaluation requirements of logic encryption, reduces problems of IC theft and IP piracy in a 
chip design stage, and can effectively prevent 
design information from being maliciously stolen, so that the security protection circuit can be universally applied to logic encryption, and has relatively strong practicability.