# Annex A Object identifiers, the normative annex

Annex A is the normative annex that assigns object identifiers to the mechanisms, so that a protocol can name the mechanism it uses without ambiguity. It is short, and it is the annex a procurement or interoperability test reads first.

## What it asks

Record the object identifier for every mechanism in use, and show that the identifier in the configuration matches the mechanism the verifier expects. Where a product reports an identifier that is not in the annex, treat it as an unregistered mechanism rather than mapping it by name.

## What the revision does

The fourth edition will reissue the identifier assignments against the revised mechanism set. The public record does not list the new assignments.

## Who it binds

The interoperability owner, procurement and the configuration manager.

## Evidence an auditor samples

- The object identifier per mechanism, with the edition it comes from (cryptography standard)
- The configuration that pins the identifier (configuration management database)
- The interoperability test that exchanges the identifier (test report)

## The test you can run

Ask two systems to name the mechanism they used. If the names differ but both are accepted, the identifier is not being enforced.

## Common failures

- Mechanisms are matched by product name rather than identifier.
- An identifier from an older edition is accepted without a mapping note.

## How to close it

Make the object identifier the key in the mechanism inventory. It is the one field that a counterparty can check without reading your documentation, which is exactly what an interoperability test needs.

## Source

ISO/IEC 9798-5:2009(E), Annex A, publisher preview; replaced by ISO/IEC DIS 9798-5, stage 40.20. Read on 21 October 2026. Our wording, not the instrument's.
https://www.iso.org/standard/89516.html

Not legal advice; does not certify.