An apparatus includes a finite state machine and a physical structure capable of providing a response to a challenge, the physical structure such that before the physical structure is ever provided with the challenge, the response to the challenge is unpredictable. The finite state machine moves from an initial state to an intermediate state due to receiving the response from the physical structure, and moves from the intermediate state to a final state due to receiving a key. The final state indicates whether the physical structure is a counterfeit physical structure.