Security of Finite State Machines in Sequential Circuits

In view of the potential security problems brought by the don't care state in the optimization of finite state machine (FSM), the definition of safe state and its design method are presented after analysis of the factors leading to intrusion into FSM and the attack paths. Without affecting the flip-flop function, state protection of FSM is realized by adding a feedback signal to the T-type flip-flop. Results show that the experimental circuit with state feedback signal is 144.7% higher than the original experimental circuit in the power consumption, delay and area; the experimental circuit optimized with T-type flip-flop is 3.6% lower than the original experimental circuit in power consumption, 18.9% lower in area, and 19.6% higher in delay.