3) E-cash. E-cash is the currency which is circulated with the electronic data form and used in purchasing goods and service though Internet. According to the authentication of bank and the credit and financial support from the bank, e-cash is accepted by the customer and merchant. If someone chooses the e-cash payment, he should purchase e-cash first. That is to say, the seller should open an account in the bank issuing e-cash and purchase e-cash. Then, by using the terminal software of PC, the seller should take out a certain number of E-cash from the bank and deposit it into the hard disk. In the transaction, purchaser should place an order for goods from the seller who can agree to receive e-cash. The purchaser encrypts the e-cash with the public key of the seller and sends the encrypted e-cash to the seller. After the seller receives the e-cash and settles accounts with the bank issuing e-cash, the bank will pay the cash to the seller and the seller should confirm the order for goods and deliver goods.