3.9 PUF Diagnostics

To determine the PUF quality, the PUF module performs a statistical analysis on various aspects of the PUF, such as randomness and noise. This is done during the Test PUF, Enroll, Start and Reconstruct operations, and results in a PUF score with a value from 0 to 7 after the operation successfully completes. A lower PUF score indicates a better PUF quality.

If the operation is not successful, the PUF score is not valid.

The PUF scores returned after Enroll (or Test PUF) give an indication of the PUF quality, while the scores after Start (or Reconstruct) provide an indication of the PUF noise level. Therefore, the scores can be different.

When a high PUF score is unexpected, the system level software must determine what actions, if any, are required.