Ned:
In my opinion, the semantics of a signature should be "I said
these words", and the interpretation of the words should be
done by a process that is defined separately from the
digital signature validation process, such as contrct law.>
Thanks Tom for your message, which gives a much better example and is far more
lucid than my explanation was. It is such a good example that I may try to use
it in the MIME-PEM draft, if that's OK with you...
Actually, according to Burrows, Abadi, and Needham "A Logic of Authentication,"
a digital signature indicates that you "once said" those words. It doesn't
say anything about when you said them, or, more important, whether you would
still say them in the present. This is not academic - especially if I'm going
to take some irrevocable action based on what I believe you believe.
-- Joe