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RE: Rambings on RFC2822 signatures.

2004-09-19 01:05:31

On Sat, 2004-09-18 at 23:58 -0500, Seth Goodman wrote:
Mailing lists have to resend it as their own outgoing message anyway.  It is
not really necessary to preserve all the signatures through the re-mailing
process.  The mailing list could validate the signature on the incoming
message, add a header or even body line indicating that fact and sign it on
the way out.  I don't really see the need for the end user to be able to
absolutely validate the identities on mailing list posts at the MUA.  That
sounds like a list function.  Lists do it now by the submitting address
(broken ones use the return-path), so they can switch to validating
signatures instead.

I disagree. That reduces it to a hop-by-hop scheme again. In order to
determine the probability that this message really did come from me,
you'd have to ponder how much you trust the list server to have actually
checked.

The idea that all MUA's would have to change to deal with displaying
multiple signed parts in different colors, as well as noting parts whose
signature doesn't validate does not bode well for adoption.

That's a purely optional optimisation. If any scheme _required_ such a
thing to be implemented by all recipients, the scheme would of course be
doomed.

I suggest we don't have to allow additions at all, in any of the MIME parts.
The irritating virus scan adverts in the message body are usually put on at
the originating or destination ends, so the signatures can be created after
the addition and validated before any subsequent addition.  Any forwarder
that puts anything in the message body rather than the headers deserves to
have his messages rejected.  That will break virtually any signature scheme,
so what is the motivation to allow this poor practice to continue?

Now you sound like the SPF folks declaring forwarding to be 'poor
practice' or 'forgery'. Let us not consider it 'poor practice'; let us
consider it 'current practice'.

And in the case of mailing lists it's a practice that some will defend
robustly. I _like_ having unsubscription instructions on every mail
which is sent to my lists. People are in general too stupid for me to
omit that.

-- 
dwmw2


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