Dave Crocker writes:
4. What is the intended lifetime for a singature? For how
long is it supposed to be valid?
For how many decades after initial delivery?
This strikes me as similar question as "how long should a
Kerberos ticket last?" Which is... completely dependent on
the local policy of the thing issuing the ticket. Mail
signatures do not strike as entirely different; they last as
long as the sender wishes them to last and no longer. I hope
that you're not suggesting that we need to pick some
arbitarary horizon here as that sounds like a good way to a
deep and unnecessary rathole.
Mike