Design Guidelines and Feedback Structure of Ring Oscillator PUF for Performance Improvement

The physical unclonable function (PUF) is a hardware security primitive that is used to generate secret keys or identity authentication for chips using random manufacturing process variation (MPV). The PUF based on ring oscillator (RO PUF) has been extensively studied in recent years because of its high robustness and ease of design. Although the performance has been optimized in previous studies, several uniqueness, reliability, and theoretical foundation concerns still remain. This article presents a transistor-level parameters-based quantitative theoretical model, which clearly reveals several design guidelines for improving the reliability of RO PUF. Furthermore, a PUF based on a feedback ring oscillator (RO) structure is proposed, which combined the RO topology and the drafting effect of XOR gates to enhance the uniqueness and reliability. The correctness of the theoretical model was verified by the SPICE simulation experiment result. And in the FPGA experiment result, the uniqueness and the reliability of feedback RO PUF using the same hardware resources on the same chip was superior to that of RO PUF. The theoretical research method of RO PUF used can be widely applied to other PUFs using ring topology and feedback RO PUF is a great substitute for RO PUF.