Physical Unclonable Functions based on Temperature Compensated Ring Oscillators

Physical unclonable functions (PUFs) are promising hardware security primitives suitable for low-cost cryptographic applications. Ring oscillator (RO) PUF is a well-received silicon PUF solution due to its ease of implementation and entropy evaluation. However, the responses of RO-PUFs are susceptible to environmental changes, in particular, to temperature variations. Additionally, a conventional RO-PUF implementation is usually more power-hungry than other PUF alternatives. This paper explores circuit-level techniques to design low-power RO-PUFs with enhanced thermal stability. We introduce a power-efficient approach based on a phase/frequency detector (PFD) to perform pairwise comparisons of ROs. We also propose a temperature compensated bulk-controlled oscillator and investigate its feasibility and usage in PFDbased RO-PUFs. Evaluation results demonstrate that the proposed techniques can effectively reduce the thermally induced errors in PUF responses while imposing a very low power overhead.