Phase calibrated ring oscillator PUF design and implementation on FPGAs

A ring oscillator physical unclonable function (RO PUF) is an application-constrained hardware security primitive that can be used for authentication and key generation. PUFs depend on variability during the fabrication process to produce random outputs that are nevertheless stable across multiple measurements. Unfortunately, RO PUFs are known to be unstable especially when implemented on an Field Programmable Gate Array (FPGA). In this work, we comprehensively evaluate the RO PUF's stability on FPGAs, and we propose a phase calibration process to improve the stability of RO PUFs. The results show that the bit errors in our PUFs are reduced to less than 1%.