A Ring Oscillator-Based PUF With Enhanced Challenge-Response Pairs

Physical unclonable functions (PUFs) are powerful security primitives that provide cheap and secure solutions for security-related applications. Strong PUFs provide a large set of challenge-response pairs (CRPs) and are suitable for device authentication. Weak PUFs produce a small number of CRPs and can be used for key extraction. In this paper, we propose a novel method to enhance the CRP set of traditional ring oscillator-based PUFs (RO-PUFs). RO-PUFs are one of the most reliable types of PUFs and the best fit to implement on the field-programmable gate arrays. To the best of our knowledge, our method provides the maximum number of CRPs compared with the state of the art. In addition, the number of response bits that can be extracted by our method for each challenge is $n-1$ times more than the state of the art, where $n$ is the number of ROs. The large number of response bits results in the authentication of more devices and generation of more keys. Evaluation of the PUF responses produced by applying our method shows a significant improvement in unpredictability and randomness compared with the related works. Moreover, we show that the responses are unique and reliable.