Keysigning challenge policies/procedures

[David Shaw]

On Fri, Jul 07, 2006 at 08:39:37PM +0200, Ingo Klöcker wrote:
> On Friday 07 July 2006 17:09, Todd Zullinger wrote:
> > Marcus Frings wrote:
> > > * Todd Zullinger <tmz at pobox.com> wrote:
> > >> What I don't see in any of the links is more information about
> > >> sending an email challenge before signing a key.  (My apologies if
> > >> I'm overlooking it on your page or any of the others.)
> > >
> > > Before I used a protocol to signing keys where I sent out random
> > > strings as challenge response but it's not worth. There is no
> > > enhanced security and only more work for "signer" and "signee". If
> > > you send the signed UIDs encrypted to each mail address separately
> > > it has the same effect in security because if the mail address
> > > bounces or the person behind the address doesn't have the private
> > > key your signed UIDs won't become publicly available.
> >
> > But that does mean that you can't get a signed key to someone if the
> > key you've signed doesn't have any encryption capabilities, correct?
> 
> That's obviously correct. In this case you could give the key owner a 
> piece of paper with a random string and ask him to send it in a signed 
> message to your email address. Then you know that he can use this key 
> for signing messages. Obviously, you can't check the validity of the 
> email addresses belonging to this key (unless he's got an encryption 
> key you can use for checking the addresses).

Sure you can: just send the random string to the email address.  If
the person can return the string back to you, signed, then you know
that there is access to both the signing key and the email address.

David