In the first article of this series we saw how the mathematics of public key cryptography could be used to create secure payment mechanisms that are analogous to bank issued notes or to bills of exchange and cheques.
Blind signatures permit, in other words, the electronic equivalent of cash.
Payments made by such methods leave no trail. This method is now being trialed in the USA and Europe by the DigiCash group in cooperation with local banks. Since each coin is identified by serial number the bank could build a spending profile of the customer by noting which merchants return the identified coins. If, however, B or some other bank is willing to exchange coins for new ones then the owner of the new coins may be unknown since all that is needed is a network address in order to conduct the transaction. The owner of the new coins would be unknown.