摘要
LOOPLock is the state-of-the-art cyclic logic locking method in hardware security. LOOPLock is able to invalidate SAT Attack, Removal Attack, and CycSAT simultaneously by introducing two types of cycle pairs in a circuit. In this work, we analyze LOOPLock&null locking mechanism and propose an attacking approach based on locking structure analysis. Furthermore, to defend the new attack, we propose LOOPLock 2.0, which strengthens the original cyclic logic locking method -LOOPLock. Experimental results show the efficiency and effectiveness of the proposed attacking approach to LOOPLock and the high defense capability of LOOPLock 2.0.