Just a thought on ways to deter all of this multiple spending gunk - when you start off, have a centralized bank server. While traffic is low, you can have each individual certificate cleared with the bank server upon creation and execution. After that, things start getting tricky. Maybe a network of bank servers linked by high priority internet links (i don't suppose there really is such a thing, but this is dreamland, after all). This would mean that to cash a certificate more than once would require very fast and accurate timing, and if you combine this with a fairly low upper limit for certificate value, it becomes a waste of time try. Oh well. Just my A$0.02. MJH * * Mikolaj J. Habryn dichro@tartarus.uwa.edu.au * "Life begins at '040." PGP Public key available by finger * "Spaghetti code means job security!"