According to the Chaum-protocol description on chaos.bsu.edu, this is an online system - both parties must talk to the bank before a transaction is concluded. Are there any true offline systems? i.e. I can send you an email which is worth money, with no third parties involved, and there is no audit trail or means of tracing. The main problem is that there is no digital "coin" or object which can be passed around but not duplicated. Other than the bank method, I've read about an "observer" chip which keeps you honest, but the design of the chip would have to be secret, or at least the chip would have to know a secret (i.e. a key) which it would never tell you. If you could extract the key, you could write a "cheater". Shades of Clipper. Is there a system which allows anonymity and at the same time prevents people from double-spending their cash? How does it work? --- MikeIngle@delphi.com