Ideally we'd be focusing on getting a charter done and holding off a
bit on the technical discussion until we knew what we were trying to
accomplish. There seems to be no hope of that happening right now, so
I might as well join the technical discussion.
Reading the domainkeys and IIM proposals, I wonder whether we're
focusing too much on security and not enough on deployability.
I realize that there was already a recent discussion on this: should the
solution be end-to-end or should it allow intermediaries.
I'd like to go farther: why are we signing the body? We're trying to
prevent spam not modification of existing mail messages. I think that
canonicalizing headers may be challenging enough; do we really need to
solve the problem of canonicalizing bodies on top of this.
It might be sufficient to sign the recipient, date and message-id (or
some other nonce) and to keep a cache of recently seen signatures.
I suspect this idea is not new; I started thinking about the minimal
set of things that needed to go into a signature after a discussion
with Jeff Schiller. However I don't yet understand why it isn't the
right approach. I bet I'm about to find out.
--Sam