It is also different from cryptography-based hardware IP protection techniques common in the design flow of Field Programmable Gate Array.
Hardware obfuscation aims at minimizing these threats at IP or chip level by making it difficult for an adversary to comprehend the actual functionality of a design.
This can be done by embedding a well-hidden finite-state machine (FSM) in the circuit to control the functional modes based on application of key.
[11] A major shortcoming of the passive approaches is that they do not modify the black box functionality of a circuit, and hence cannot prevent potential usage of an IP as black-box in a design.
IBM, in order to maintain some competitive advantage, implemented secret opcodes that would only be used by the closed source operating system on the mainframe.