The undetectable clock cycle sensitive hardware trojan

We have proposed a method of designing embedded clock-cycle-sensitive Hardware Trojans (HTs) to manipulate finite state machine (FSM). By using pipeline to choose and customize critical path, the Trojans can facilitate a series of attack and need no redundant circuits. One cannot detect any malicious architecture through logic analysis because the proposed circuitry is the part of FSM. Furthermore, this kind of HTs alerts the trusted systems designers to the importance of clock tree structure. The attackers may utilize modified clock to bypass certain security model or change the circuit behavior.