Unleashing the Full Potential: Increasing the Bit Configuration Options in Configurable Ring Oscillator PUF

Physically unclonable functions (PUFs) are essential primitives for enhancing hardware security, leveraging the variations in physical characteristics of integrated circuits (ICs) that happen during the manufacturing process. Among various PUF designs, the Ring Oscillator (RO) PUF offers design simplicity and high performance. However, RO-PUFs have been limited in their input-output combinations or what is referred to as challenge-response pairs (CRPs) within the scope of PUFs, classifying them as weak PUFs. Consequently, increasing the CRPs size of the RO-PUF will result in an enhancement of the PUF's overall security attributes. Increasing the CRPs size of a RO-PUF can be achieved through two main methods. Firstly, by increasing the number of ring oscillators in the design which leads to greater hardware demands. Secondly, configurability can be introduced into the individual ring oscillators of the RO-PUF without imposing a substantial demand on hardware resources. Therefore, this paper utilizes the configurability approach to maximize the size of the CRPs set. The evaluation process conducted in this study demonstrates that the proposed design provides excellent results across several performance metrics.