Subject: q re binding user id's and subkeys

From: Erron Criddle <[email-masked]>
Date: Wed, 14 Jun 2000 13:52:51 +0800

To all,

Regarding 5.5.1.1 and 5.5.1.2; I am having a problem trying to understand 
how one binds an encryption sub key to a particular user id and the top 
level signing key?

There seems to be no information contained in a sub-key packet that can 
link it to a user id. Also, the binding signature does not contain info 
regarding a user id (nor the binding signatures subpackets).

By binding an encryption sub key to a primary signing key, you are binding 
it to multiple user id's (if multiple user id's exist), however if user id 
(a) wants to encrypt data using sub-key (b) and user id (b) wants to 
encrypt data using sub-key (a), where do you actually make the bind?

My apologies if I've (once again), misread or completely missed something.

Regards

Erron Criddle
Comasp Ltd.
Level 2, 45 Stirling Hwy
NEDLANDS  WA  6009

Fax: 08 9386 9473
Tel: 08 9386 9534

http://www.comasp.com
[email-masked]

---

From: [email-masked]
Date: Sun, 16 Jul 2000 16:18:21 -0700

Erron Criddle writes:

> >There is no way to express this in OpenPGP.
>
> Would it be hard to express that in OpenPGP? Can a signature subkey be 
> added that specifies the top level id that should be linked to the subkey? 
> Accordingly, if the subkey is bound to all upper level id's (as is the case 
> now) then the signature subkey would simply be left blank.

Well, there is no way to express that in OpenPGP.  If you are asking,
could we add a way to do that, the answer is that it would be technically
possible.  The question is whether there is sufficient desire to add that.

I think if you wanted to do this, it would be better to add a way for
a given userid self-sig to say which subkey to use when that userid
was chosen as an encryption target, rather than the other way around
(subkey to point at userid).

Without this mechanism, the main use of multiple subkeys is to make
it easy to roll over your encryption keys relatively often, without
invalidating the validity of your key.  That's an important piece of
functionality in itself.

We might wish to discuss whether it is worthwhile to go beyond this to
also allow the use of different subkeys for different userids.  It would
add considerable complexity to the UI, and at PGP.com we are if anything
trying to simplify the UI.  Most users still say encryption is too hard
to use.

Hal Finney