"Treat as unsigned" seems a little ambiguous when there might be
multiple signatures. It might be interpreted as "treat the message as
though it is completely unsigned" as opposed to "consider this signature
invalid" which I think is your intent.
I don't think the wording "consider this signature invalid" requires the
verifier to consider a signature failure as "unsigned".
When a signature fails to validate, the message should be processed as
if that signature is not present.
d/
--
Dave Crocker
Brandenburg InternetWorking
<http://bbiw.net>
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