Image PUF: A Physical Unclonable Function for Printed Electronics based on Optical Variation of Printed Inks
Printed Electronics (PE) has a rapidly growing market, thus, the counterfeiting/overbuilding of PE components is anticipated to grow. The common solution for the counterfeiting is Physical Unclonable Functions (PUFs). In PUFs, a unique fingerprint is extracted from (irreproduceable) process variations in the production and used in the authentication of valid components. Many commonly used PUFs are electrical PUFs by leveraging the impact of process variations on electrical properties of devices, circuits and chips. Hence, they add overhead to the production which results in additional costs. While such costs may be negligible for many application domains targeted by silicon-based VLSI technologies, they are detrimental to the ultra-low-cost PE applications. In this paper, we propose an optical PUF (iPUF) extracting a fingerprint from the optically visible variation of printed inks in the PE components. Since iPUF does not require any additional circuitry, the PUF production cost consists of merely acquisition, processing and saving an image of the circuit components, matching the requirements of ultra-low-cost margin applications of PE. To further decrease the storage costs for iPUF, we utilize image downscaling resulting in a compression rate of 484x, while still preserving the reliability and uniqueness of the fingerprints. The proposed fingerprint extraction methodology is applied to four datasets for evaluation. The results show that the process variation of the optical shapes of printed inks is suitable as an optical PUF to prevent counterfeiting in PE.