FIPS 140-3 Entropy evidence

Start with the entropy path, not the product claim. The evidence should identify whether the module generates entropy itself, calls a well-defined source through a GetEntropy() interface, passively receives externally supplied entropy, or combines active and passive inputs. CMVP Implementation Guidance 9.3.A treats those cases differently because the laboratory may be able to corroborate some entropy-strength estimates directly while other deployments require warning caveats.

The core record should therefore include the module boundary, TOEPP or physical perimeter, source location, interface type, DRBG seeding path, and the minimum bits of entropy generated, requested, accepted, or believed to have been loaded for SSP generation. A statement that the product uses a DRBG is not enough; the question is whether the seeding evidence supports the strength claim being made for generated SSPs.

When an entropy evaluation is required, CMVP guidance points teams to SP 800-90B and IG D.K. The evidence package should include raw noise-source access details, statistical-test results, the entropy assessment tool version, and the laboratory's heuristic analysis of how the noise source works and why the claimed entropy rate is supported.

The Security Policy should document the overall generated entropy and the estimated entropy per source output bit when SP 800-90B testing applies. If the vendor claims IID behavior, the support needs to be rigorous and should address independence and identical distribution separately; the guidance warns that most noise sources do not produce IID events.

Review the Security Policy and certificate together. CMVP guidance requires different public statements depending on whether the module uses an internal source, a known source inside the TOEPP, an external source, a passive load, or a hybrid design. If entropy is externally loaded or cannot be directly verified for all deployments, the certificate may need a no-assurance caveat rather than a broad strength claim.

For multiple entropy sources, do not add entropy by intuition. CMVP guidance allows concatenating outputs from multiple independent SP 800-90B-compliant sources for a DRBG seed, but the Security Policy should explain which sources are creditable, whether they are physical or non-physical, and which method is used for entropy calculation. If sources are mutually dependent, at most one of those dependent sources may be credited.