A transmission gate physical unclonable function and on-chip voltage-to-digital conversion technique

A physical unclonable function (PUF) is an embedded integrated circuit (IC) structure that is designed to leverage naturally occurring variations to produce a random bitstring. In this paper, we evaluate a PUF which leverages resistance variations which occur in transmission gates (TGs) of ICs. We also investigate a novel on-chip technique for converting the voltage drops produced by TGs into a digital code, i.e., a voltage-to-digital converter (VDC). The analysis is carried out on data measured from chips subjected to temperature variations over the range of -40°C to +85°C and voltage variations of +/- 10% of the nominal supply voltage. The TG PUF and VDC produce high quality bitstrings that perform exceptionally well under statistical metrics including stability, randomness and uniqueness.