[1][2][3][4] A hardware security module (HSM) is a physical computing device that safeguards and manages digital keys for strong authentication and provides cryptoprocessing.
These modules traditionally come in the form of a plug-in card or an external device that attaches directly to a computer or network server.
Conceptionally related, a hardware Trojan (HT) is a malicious modification of electronic system, particularly in the context of integrated circuit.
Further, an individual PUF device must be easy to make but practically impossible to duplicate, even given the exact manufacturing process that produced it.
Today, PUFs are usually implemented in integrated circuits and are typically used in applications with high security requirements.