Douglas Otis wrote:
Although Jim Fenton has suggested currently these signature structures
are independent of any existing header, this would seem to make it
difficult for the signing domain to be visible anytime soon, however.
I'm not sure it was really my suggestion to make them independent, but
there seems to be such a visibility issue even if they are tied to an
existing header, we might as well make them independent and then decide
how to make the address associated with the signature visible.
If I remember some of the solutions for visibility, one was to add a
comment within the From pretty-name indicating the domain used to sign
the message. (Placed there during the validation process.)
That's a suggestion that is made in the IIM spec somewhere. It probably
doesn't belong in any of the specs, but rather in a "best practices"
document that we probably need describing how to deploy message
signing/verification. Rewriting the pretty-name is really a way to do
something useful until MUAs have a better way to make the signer address
visible.
I suggested another method would be to flip how Resent-Sender and Sender
are handled in the case of user forwarding. Normally the intent is to
leave the message appear as if there are no changes to its content.
Obviously, applying a new signature would remove an assurance nothing
has changed. One could view the use of Sender the best header for
referencing a signature, but what happens when this message is forwarded
by the User. They typically want to preserve the From.
When you say "flip" it makes it sound like there is exactly one
Resent-Sender, and that's not necessarily the case. I suppose you could
define which one (probably the first) gets swapped. But what happens if
the message gets verified in more than one place?
With the pretty-name rewriting hack, it's possible to verify multiple
times if there's a reliable original version of the From header (e.g.,
the copied From header in IIM). Each time the verification happens you
start with the pretty-name on the original From header.
-Jim