Development of a simple contact-type printable physically unclonable function device using percolation conduction of rod-like conductive fillers

We suggested a printable physically unclonable function (PUF) with a simple circuit structure, to provide a low-cost PUF for improvement in the security level of electronic devices. An element of our contact-type printable PUF was constructed of a conductive filler layer and a pair of electrodes formed by printing. The contact-type printable PUF was based on an open- or short-circuit information of elements induced by a percolation conduction phenomenon of the conductive filler layer. An average conduction probability of the elements could be controlled by adjusting the manufacturing conditions, but an actual appearance pattern of the conduction elements became completely random by the influence of the uncontrollable printing variations. We fabricated a thousand elements for each printing condition to evaluate the PUF performance statistically and obtained a random conduction pattern with a conduction probability of 48.3%. Therefore, our contact-type printable PUF had enough potential to be used as a PUF security system.