Bryce <wilcoxb@nag.cs.colorado.edu> writes:
Perhaps a similar "polymorphism" could be implemented with regard to on-line/off-line clearing. When you as a payee receive a Chaumian Ecash coin, you can choose based on several factors (including reputation of the payer if he chooses to make his nym known to you, size of the transaction, time of day, or whatever) to either accept it immediately and credit the payer with whatever it is you are selling, or to delay completion of the transaction while you attempt to deposit the coin with your e-bank. (If you are wary of "payee-ID proof stings" like Lucky Green is, then you can go ahead and launder your coin through an anon account during this interval...) If your payer has already spent this coin, then the bank will inform you immediately and you can cancel the transaction. (And take whatever other actions you consider appropriate...)
Unfortunately, in order for a coin to be POTENTIALLY spent in an off-line way, the protocols require that the identity of the withdrawer be embedded, in blinded form, within the coin data. It is this step that Tim and others object to, because among other things it requires participants to securely identify themselves to the bank, hence does not work well in a fully anonymous society. The reason for this requirement is that if the coin is double-spent, this is not found out until afterwards, and so the identity of the cheater has to be available so the bank can go after him. So letting the payee choose whether to deposit the coin right away or wait until later will not address this basic privacy problem with offline cash. Hal