A practical circuit fingerprinting method utilizing observability don't care conditions

Circuit fingerprinting is a method that adds unique features into each copy of a circuit such that they can be identified for the purpose of tracing intellectual property (IP) piracy. It is challenging to develop effective fingerprinting techniques because each copy of the IP must be made different, which increases the design and manufacturing cost. In this paper, we explore the Observability Don't Care (ODC) conditions to create multiple fingerprinting copies of a design IP (e.g. in the form of gate level layout) with minute changes. More specifically, we find locations in the given circuit layout where we can replace a gate with another gate and some wires without changing the functionality of the circuit. However, as expected, this could introduce design overhead. Our experimental results show that, although we can embed fingerprints of up to 1438 bits, there is an average of 10.9% area increase, 50.5% delay increase, and 9.4% power increase on circuits in the MCNC and ISCAS 85 benchmark suites. We further propose a fingerprinting heuristics under delay constraints to help us reduce area and power overhead.