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6.13.5.5
The group equation, with the curve parameters in hand
The verifier runs the signature equation with the curve parameters and the base point of the set, and accepts or rejects. Everything the equation needs has been checked in the preceding steps, so this step is arithmetic on values that are known to be in range and on the curve.
- What it asks
- Run the equation with the parameters of the set the deployment uses, and record the accept and reject result for the worked examples. Where a library provides the whole verification, record which clause revision the library implements, because a library built before the amendment may not enforce the decoding rules.
- What the amendment does
- Inserts 6.13.5.5. So this is new text rather than a change to wording.
- Who it binds
- The verifier owner and the library owner.
- Evidence an auditor samples
- The worked example results, accept and reject, in the test log (test suite)
- The library version and its statement of the clause it implements (supplier file)
- The upgrade plan for any library that predates the amendment (remediation plan)
- The test you can run
- Run the two worked examples and one mutated signature. Two accepts and one reject is the expected result; anything else is a finding.
- Common failures
- The library is assumed to implement the amendment because it supports the curve name.
- The verifier accepts a signature when the decode step was skipped.
- How to close it
- The equation is the easy part. The evidence that matters is the negative case, because a verifier that always returns true still passes the positive example. Keep one mutated signature in the suite for exactly that reason. Put the worked example results, accept and reject, in the test log in the register first, then work down the evidence list until every line has a date.
- Where it sits against the base standard
- The base standard does not carry this text. The amendment adds it, so an estate working from the 2018 edition alone will not find it. The citation has to name the amendment, and the record for 6.13.5.5 is the only place a reader can see it.