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FAQGLOBALFIPS 140-3

FIPS 140-3 Entropy evidence

A direct answer on what entropy evidence should show before a team relies on a FIPS 140-3 module, DRBG, or SSP-generation claim.

Based on FIPS 140-3 and CMVP Implementation Guidance; it does not assert that any specific source, DRBG, module, or certificate is approved.

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Author
Sorena AI
Published
May 9, 2026
Updated
Jul 24, 2026
Questions
3

Structured answer sets in this page tree.

Primary sources
4

Cited legal and guidance references.

Publication metadata
Sorena AI
Published May 9, 2026
Updated Jul 24, 2026
Overview

Under FIPS 140-3, should show how the module obtains entropy, where the source sits relative to the cryptographic boundary or tested operational environment physical perimeter, what minimum entropy amount is claimed for SSP generation, and how that claim is reflected in the Security Policy, test report, and any certificate caveat.

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3 of 3 questions
Question 1

What should entropy evidence answer first?

Start with the entropy path. The evidence should identify whether the module generates entropy itself, directly 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 assigns different evidence and certificate caveats to those cases because the laboratory can corroborate some entropy estimates but cannot guarantee the quality of entropy supplied by an uncontrolled external source.

The core record should include the module boundary, or physical perimeter, source location, interface type, seeding path, and the minimum bits of entropy generated, requested, accepted, or believed to have been loaded for SSP generation. The DRBG name alone cannot support a generated-SSP strength claim; the seeding evidence must support that claim.

  • Map every entropy source to the cryptographic boundary, , physical perimeter, and instantiation or reseed event it supports.
  • Distinguish direct GetEntropy() access from seed loaders, LOAD commands, preloaded seeds, caller-supplied API buffers, files, and other passive inputs.
  • Record the minimum entropy amount used for SSP generation and the evidence basis for that amount.
  • Check whether the design triggers a certificate caveat such as modified SSP strength or no assurance of minimum generated-SSP strength.
Citations
Recommended next step

Operationalize FIPS 140-3 entropy evidence

Use the entropy path, Security Policy, test-report addendum, certificate caveat, ESV or ENT notation, and CAVP records as one review set.

Assessment workflow
Turn entropy evidence into controls

Convert entropy-source, SP 800-90B, Security Policy, and caveat checks into accountable evidence requests.

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Research workflow
Research a FIPS source question

Resolve CMVP guidance, CAVP record, ESV, and module-scope questions before procurement or release review.

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Talk to Sorena
Talk through entropy evidence

Review module scope, entropy-source evidence, caveats, and next validation-support actions with Sorena.

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Question 2

What SP 800-90B evidence belongs in the file?

When an entropy source validation is required, CMVP guidance points to SP 800-90B, IG D.J, and IG D.K. A source within a software, firmware, or hybrid module's that supports an available-entropy claim requires an certificate and a direct path from the module to the source's GetEntropy() interface. The evidence package must 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 must 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 must be rigorous and must substantiate independence and identical distribution separately; the guidance warns that most noise sources do not produce IID events.

  • Keep the entropy-source description, raw data collection method, and rationale that collection does not alter source behavior.
  • Attach statistical-test outputs and the version of the CMVP SP 800-90B entropy assessment tool used.
  • Include the heuristic entropy analysis, not only the statistical-test result.
  • Document known or suspected noise-source failure modes and the health tests intended to detect them.
Citations
Question 3

How should teams review Security Policy and certificate evidence?

Review the Security Policy, evidence, and module certificate together. CMVP guidance requires different public statements depending on whether the module uses an internal source, a known source inside the , an external source, a passive load, or a hybrid design. An ESV certificate supports the evaluated entropy source; it does not replace the module's CMVP certificate. If entropy is externally loaded or cannot be corroborated for the deployed configuration, the module 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 seed, but the Security Policy must 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.

  • Compare the design description, Security Policy entropy statement, or ENT notation, and certificate caveat for the same module version.
  • Confirm that caller guidance is present when an external party must provide entropy with a minimum claimed strength.
  • For multiple sources, document independence before summing credited entropy.
  • Do not treat a CAVP algorithm certificate, name, or generic FIPS reference as proof that the module's supports the deployed configuration.
Citations
NIST CAVP validation search

CAVP records can support approved algorithm implementation checks, but algorithm evidence does not by itself establish module boundary or entropy-source validity.

Primary sources

References and citations

NIST CAVP validation search
csrc.nist.gov
Referenced sections
  • CAVP records can support approved algorithm implementation checks, but algorithm evidence does not by itself establish module boundary or entropy-source validity.
NIST SP 800-90B entropy assessment tool
github.com
Referenced sections
  • CMVP guidance cites this public tool for SP 800-90B statistical testing; the tool output does not supersede the lab's heuristic analysis.
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