MH Michael Hammer (5304) wrote:
How does a 3rd party signing a message change the intent of the author
of a message? One might argue that breaking the original signature does that.
My response would be to then avoid breaking the original signature.
One of the arguments put forward supporting the DKIM effort was that unlike
SPF it is not hop dependent.
A common source of confusion about this is the difference between an MTA Relay
and a Mailing List Mediator. A DKIM signature always survives relaying,
whereas
SPF registration cannot any.
Whether a DKIM signature survives the re-submission by a Mediator is a very
different matter. "The intent of the author" is something the Mediator might
or
might not choose to pay attention to -- assuming automated software can intuit
an author's intent -- since Mediators vary quite a lot, including Mailing Lists.
The reality is that after receiving the message, the Mediator owns it and can
legitimately do whatever it wants. Or rather, any constraints on its actions
depend on policies and agreements that are far outside the realm of current
email protocol standards.
That some Mediators choose to do minimal violence on a message and -- as an
unintended side-effect -- happen to preserve a DKIM signature is very nice, but
hardly something that can be legislated (or safely protected assured.)
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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