Improving the Reliability of FPGA CRO PUFs

This paper presents a novel technique that greatly improves the reliability of FPGA-based CRO PUFs. We improve upon existing CRO implementations and increase the number of configurations per CLB tile from 16 384 to 1.1 × 10¹²• To maximize reliability, each CRO pair must be configured to maximize its frequency difference. This requires using a novel technique that reduces the configuration search space from 1.1 × 10¹² to 256. Our CRO PUF achieves 100% reliability within the FPGA's maximum rated voltages. We believe that this is the first FPGA PUF that can achieve this level of reliability without the use of post-processing. We also show that in some cases, our CRO may be reliable enough to omit the ECC that is usually required in PUF-based key generation circuits. This allows our CRO PUF to provide the reliability required for key generation while reducing the latency, complexity, and area overhead of ECC algorithms.