Optimizing CPU Jitter Analysis: Lessons Learned from Applying the New Heuristic Procedure (G30a)
As of January 1st, 2025, the CMVP requires a more rigorous heuristic analysis for non-physical entropy sources to justify the amount of entropy claimed in Entropy Source Validation (ESV) submissions. As of that date, CMVP also requires the use of a new CPU Jitter heuristic procedure. It is a new procedure for analyzing CPU Jitter that considers the system memory depth of the noise source on a particular hardware. The system memory depth is related to the optimal oversampling rate (OSR), which is related to the min-entropy of CPU Jitter implementations. The min-entropy rate of CPU Jitter is 1/OSR. The default OSR is 3, and this is what most vendors initialize CPU Jitter with. However, this may not be the optimal OSR for every OE. With this new procedure the speakers investigate which is the optimal OSR and in doing so the speakers find and justify the min-entropy rate in each OE. The speakers have developed a step by step test plan with Joshua Hill from KeyPair Consulting based on this new heuristic procedure to determine the value of the optimal OSR, H_heuristic, and H_submitter for each OE. In this talk the speakers will share experiences and lessons learned while utilizing the new procedure.