multiple subkeys and key transition

[David Shaw]

On Dec 11, 2010, at 2:55 PM, Ben McGinnes wrote:

>> You can't actually turn on or off certify (which is to sign a key -
>> either your own or someone elses).  In OpenPGP, the primary key can
>> always certify (it may be able to encrypt/sign/authenticate as well,
>> but the only strict requirement is that it must be able to certify).
>> Without the ability to certify, you could never make a subkey, since
>> subkeys are signed by the primary key.
> 
> Cool.  On a tangential note, could this be used as a basis for
> applying a PKI/WoT model to certification of SSL keys, rather than
> relying on CAs?

Yes indeed.  See http://web.monkeysphere.info/ for a project using the WoT for both SSH and HTTPS.

>> Once you make that primary key, you just add subkeys for whatever
>> capabilities you desire.  Again, the defaults are recommended (they
>> are correct for virtually everyone).  I'd add a sign-only subkey and
>> an encrypt-only subkey.  GnuPG will automatically use the subkey for
>> signing over the primary key for signing.
> 
> I assume this means that if the primary key can sign & certify, that
> key will still be used to sign other keys even if there is a specific
> signing subkey for messages and files.  Right?

Right.  Since only the primary can certify, it will be automatically chosen whenever you try to sign another key.

David