Home / The record / Annexes

Annex C is the informative guidance on parameter choice and on comparing the mechanisms. It is where a design team looks for a modulus size, a challenge length or a reason to prefer one family, and it is the annex most often quoted without its informative status.

What it asks

Record the guidance you relied on, the parameter you chose and the reason, and mark the citation as informative. Where the guidance gives a range, record the point in the range and the constraint that fixed it, rather than quoting the range as if it were a requirement.

What the revision does

The fourth edition will update the guidance for the revised mechanism set. The public record stops before the new text. The annex keeps its 2009 material and gains the revision, which a copy of the older annex will not have.

Who it binds

The architect who chose the parameters and the reviewer who accepted them.

Evidence an auditor samples

• The parameter choice record, with the guidance citation and its status (design note)
• The constraint that fixed the point in the range (capacity plan)
• The review that accepted the choice (risk register)

The test you can run

Take a parameter and ask which constraint fixed it. If the answer is a range with no point, the choice has not been made.

Common failures

• A range from the guidance is quoted as the approved value.
• The guidance is cited without saying it is informative.

How to close it

Write the constraint before the number. A parameter chosen against a named constraint survives a review; a parameter copied from a table does not. Start with the parameter choice record, with the guidance citation and its status and let the row close when it exists with a date and a named holder.

Where it sits against the 2009 edition

The annex is in the 2009 edition, and the fourth edition carries forward it in revised form. A copy of the 2009 annex is not the annex the new edition will publish.

For the file, this row closes when the parameter choice record, with the guidance citation and its status exists with a date, a named holder and a pointer, and when the test above has been run and recorded. The architect who chose the parameters and the reviewer who accepted them. owns that answer for Annex C.