Subject: Re: Interop grill-off

From: [email-masked] ("Hal Finney")
Date: Tue, 20 Sep 2005 10:33:37 -0700 (PDT)

David Shaw writes:
> I don't know of *any* implementations that set the issuer subpacket to
> anything other than the key that made the signature, as specified in
> the RFC.  Doing otherwise would be an absurd thing to do - the signing
> equivalent of putting the main key ID into a PKESK packet when
> encrypting to a subkey.  If you can point to a single implementation
> that does this wrong, I'll immediately concede the point.

Perhaps we should clarify the language in the RFC to eliminate any
such ambiguity.  5.2.3.5, the Issuer subpacket, just says:

    The OpenPGP key ID of the key issuing the signature.

We could add "If the signature is issued by a subkey then the key ID of
this subkey is used here instead of the key ID of the primary key."

We do have similar language in 5.2 for PKESKs:

      - An eight-octet number that gives the key ID of the public key
        that the session key is encrypted to. If the session key is
        encrypted to a subkey then the key ID of this subkey is used
        here instead of the key ID of the primary key.

This would make sure there is no ambiguity about which key ID to use.

Hal Finney

---

From: David Shaw <[email-masked]>
Date: Tue, 20 Sep 2005 14:06:51 -0400

>         here instead of the key ID of the primary key.

I think that is reasonable, but it would need to be mentioned in
several places (in bis-14): 5.2.2 (V3 signatures), 5.2.3.5 (issuer
subpacket), and 5.4 (Onepass signature packet).  Perhaps something
could be said in 3.3 (Key IDs) that covers them all?

David