Graphene physically unclonable function Graphene transistors have been used to create a physically unclonable function (a PUF) – one of the key building blocks of high-end on-chip security. PUFs create numbers from the fine-grained randomness found in in an individual IC, due to doping and manufacturing variations, for example. In this case, variations in the carrier transport of graphene transistors was used, which follow Gaussian random distributions, according to Penn State University, where the PUF was made. The team first fabricated nearly 2,000 graphene transistors, intended to be identical, but with variations due to differences in Dirac voltage, Dirac conductance and carrier mobility.