clarify certification key flag limitation

This commit is contained in:
Heiko Schaefer 2023-11-28 19:37:06 +01:00
parent e187175d65
commit e59e70939c
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GPG key ID: DAE9A9050FCCF1EB

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@ -49,9 +49,11 @@ Third-party signatures are used to make specific statements:
- revoking, and thus invalidating, prior third-party signature statements
```{note}
The **certify others** [key flag](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-key-flags) (`0x01`) is required to issue third-party signatures. Typically, only the certificate's primary can hold this key flag.
The **certify others** [key flag](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-key-flags) (`0x01`) is required to issue third-party signatures. By convention[^primary-certification], only the certificate's primary can hold this key flag.
```
[^primary-certification]: Implementations currently assume that only the primary key may hold the "certify others" key flag. However, the RFC doesn't clearly specify this limitation.
### Distinct functions of self-signatures and third-party signatures
The meaning of an OpenPGP signature depends significantly on its issuer. Self-signatures and third-party signatures, even when of the same [signature type](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-signature-types), serve distinct functions. For example: