Long-term stability of organic physically unclonable function for IoE security

Abstract

We evaluated long-term stability of organic security circuit for future IoE society. Physically unclonable function (PUF) was chosen as basic technology in this study, because PUF utilized dynamic information such as characteristics variation in devices and it was expected to show high tamper resistance. In addition, we utilized organic semiconductor because of its advantage for flexibility. At first, we fabricated organic thin film transistor array to measure current variation. Comparing current in on-state of organic transistor, we obtained 19-bit unique number depending on a chip. During measurement for 6 months, on-current gradually decreased as time goes by. However, the unique number was generated stably with low bit error rate below 11% when we set benchmark to data at 7th day after fabrication. It means the unique number can be handled as device ID. It is because organic transistors degraded uniformly over all. As a result, our organic transistor array works well as PUF even after 174 days.