Theoretical Analysis of Configurable RO PUFs and Strategies to Enhance Security

Compared to traditional ring oscillator PUF (RO PUF), configurable RO PUF (CRO PUF) greatly increases the number of challenge response pairs (CRPs) and improves hardware utilization. However, in the conventional CRO PUF design, when a path is selected by the challenge to generate a response, the circuit characteristic information constituting the CRO PUF, such as the delay information of the configurable unit, the transmission model, and etc., can also be leaked. Once the adversary monitors and masters this information, they can use this information to attack the CRO PUF circuits, such as modeling attacks. This paper establishes a theoretical model of CRO PUF and analyzes its unpredictability and security. Based on this model, a new mechanism to generate the proper challenges is proposed in this paper. In the proposed mechanism, the challenge is generated and utilized by a specific way, which can delay the feature leakage of the CRO PUF, thereby improving the security of the CRO PUF.