PUFs: Standardization and Evaluation

Physically unclonable functions (PUFs) serve as untamperable secrets buried in a device thatmust meet some properties in order to be securely used in cryptographic protocols. Due to the stealthy nature of PUFs, the verification of these properties is in itself a difficult task. In this paper, we survey the current trends regarding those aspects. An international standard working draft is described which handles the accurate and consensual definition of the required properties and also covers the high-level methodology related to the test of PUFs. Some in-depth examples of evaluation procedures are also described, bothbefore the fabrication (illustrated on entropy measurement) andafter the fabrication (illustrated on reliability analysis—especially how it withstands aging). These evaluations are carried out on the loop-PUF structure, a delay-PUF for which a simple stochastic model can be derived.