Regarding the issue of what to do under Chaum's scheme when someone double- spends a piece of digital cash & their identity is revealed... While this might be a problem for a cypherpunk style "kick society in the pants and get this going early" implementation of digital banking, I don't think it's going to be a serious hindrance in the long term. While I'm sure all big retail chains and the like will have terminals that can instantly verify a piece of cash, if there are niches for an offline system, there's a very significant economic infrastructure set up for collecting on bad debts. Any credit card company, phone company, or other corporation that does a lot of billing already has staff dedicated solely to that function, with collection agencies providing a second tier of functionality for the tougher cases. Dr. Cat / Dragon's Eye / New traditions for the next century