RE: Message protection and key update

[Carlisle Adams <carlisle.adams@xxxxxxxxxxx>]

Hi Chris,

> ----------
> From: 	Christopher Williams[SMTP:ccwilliams@ntlworld.com]
> Sent: 	Thursday, May 04, 2000 11:53 AM
> To: 	PKIX Mailing List
> Subject: 	Message protection and key update
> 
> Consider the following scenario:
> 
> I am enrolled in a PKI and have a signing-key pair that I wish to update.
> I
> send a key update request containing a new public key.  I sign the message
> using my old private key.  The request is granted by the CA so I send a
> certificate confirm message.
> 
> I assume that I sign this message with my NEW private key.  Is this
> correct?
 
You can sign with the new private key if you wish, but the old private key
would be fine as well (and, in fact, it may be slightly preferable to have
the consistency of a single method for all the messages in an exchange).

> Also, does this signature provide implicit POP of the private key?  After
> all, the signature is over the hash of a certificate containing the
> matching
> public key.  If it does provide implicit POP, should the POP options be
> expanded?
 
Don't think of this as providing implicit POP.  [If signing the hash of the
cert is POP, what about the hash-of-the-hash of a cert?  What about the
hash-of-the-hash-of-the-hash of the cert?  I think it's best not to go down
this route at all.]  This is simply authentication and integrity protection
on the message.

Carlisle.