Physical unclonable functions (PUFs) have broad application prospects in the field of hardware security. Like faults in general-purpose circuits, faults may also occur in PUFs. Fault diagnosis plays an important role in the yield learning process. Traditional fault diagnosis methods are based on comparing the fault-free responses of a design and the failing responses of chips. However, different manufactured, fault-free PUFs with the same design have different challenge-response pairs, so PUFs do not have deterministic, fault-free responses. Hence, traditional fault diagnosis methods are unsuitable for PUFs. To effectively diagnose PUFs, this paper proposes a diagnostic challenge generation method for the typical PUF: arbiter PUF. The diagnostic challenges that can deterministically or probabilistically distinguish the suspect faults of arbiter PUFs are generated. Simulation experiments on diagnosing failing arbiter PUF instances show that all the actual fault locations are accurately included in the candidate sets, and the average number of candidate locations (i.e., diagnostic resolution) is 1.585. FPGA experiments on diagnosing real PUFs show that the diagnostic accuracy is also 1, and the average diagnostic resolution is 1.602.
