Primary uid - significant when?

After following David Shaw's advice to look at RFC-2440 I understand that
uids are bound to keys using signatures, and that one can add more uids to
a key (using gpg --edit-key >> adduid, for example).

So we can have many uids for one key.

I see that one uid for a key is marked as the primary uid. My
understanding is that there is one and only one primary uid for a key,
but that the primary uid can be changed (using gpg --edit-key >> primary,
for example).

OK, but what is the significance of the primary uid? When does it matter
what the primary uid is?

Many thanks,
Bruce

Bruce Badger wrote:[color=blue]
> OK, but what is the significance of the primary uid?
> When does it matter what the primary uid is?[/color]

It is used when you list key signatures
(gpg --list-key -v or --check-sig)

--
You can use "pkg_info" to see a list of packages you have installed.

Igor Ivanov <i+usenet3f41f42b@gambit.com.ru> wrote in
news:slrnbk3t4h.am.i+usenet@gambit.com.ru:
[color=blue][color=green]
>> OK, but what is the significance of the primary uid?
>> When does it matter what the primary uid is?[/color]
>
> It is used when you list key signatures
> (gpg --list-key -v or --check-sig)[/color]

I don't know about GPG, but for PGP, it is also who will show as having
signed when doing a signature verification.

--
Tom McCune
My PGP Page & FAQ: [url]http://www.McCune.cc/PGP.htm[/url]

Bruce Badger wrote:[color=blue]
> After following David Shaw's advice to look at RFC-2440 I understand that
> uids are bound to keys using signatures, and that one can add more uids to
> a key (using gpg --edit-key >> adduid, for example).
>
> So we can have many uids for one key.
>
> I see that one uid for a key is marked as the primary uid. My
> understanding is that there is one and only one primary uid for a key,
> but that the primary uid can be changed (using gpg --edit-key >> primary,
> for example).
>
> OK, but what is the significance of the primary uid? When does it matter
> what the primary uid is?[/color]

It is used in a few places. If you refer to a key by a user ID name,
the cipher preferences used for that session are that of the particular
user ID. If you refer to a key by a keyid, the cipher preferences for
that session are that of the primary user ID.

It is the user ID that is listed first when you verify a signature.

It is the user ID that is listed first in --list-keys.

It is the user ID that shows up in --list-sigs when you see who has
signed a key.

Basically, it's a way for the user to indicate a particular user ID as
the one to use when in doubt. If the user doesn't set a primary, GnuPG
assumes the most recently created user ID is the primary.

David