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An alternative way to do 1-of-N certificates?

While I'm asking about some of the things in the SPKI draft, here's
another possibility: I think there's an alternative secure way to do
1-of-N certificates that might be more convenient and flexible while
still retaining security, though I'm not so sure it's as easy to
reason about.  To delegate a fraction of a priviledge, delegate the
priviledge to a local name that you control, but don't directly
certify that name as belonging to any key.  Instead write people
certificates entitling them to some fraction of that name, and use
rational arithmetic in the verifier to make sure that all the
fractions approving an action add up to one.  This I think allows you
to do all the arbitrarily subtle things that secret sharing schemes
can do while keeping it to a fairly simple framework.

\/ o\ paul@hedonism.demon.co.uk  http://www.hedonism.demon.co.uk/paul/ \ /
/\__/ Paul Crowley            Upgrade your legacy NT machines to Linux /~\