(Authentication and blind signature protocol between banks and users)

1. User → Bank: The user first proves to the bank that he is the holder of his account through an identity agreement (such as schnorr agreement), and then transmits the withdrawal request (face value and quantity of electronic cash, etc.). ) to the bank;

2. Bank → User: The bank first verifies the identity information submitted by the user, then selects w∈RZq, calculates a 0=gw, b0=(I Ug 2)w, z0 = (I Ug 2)x, and sends a 0, b0 and z0 to the user.

3. user → bank: select x 1, x 2, s, u, v∈RZq, and calculate B=g 1 x 1g 2 x2, A=(I Ug 2) s, z = (z0) s, a =

4. bank → user: calculate r 0= w+c 0x mod q, send r 0 to the user, and debit the user account at the same time.

5. User: check gr 0 yc0a 0 and (I Ug 2)r0 (z0)c0b0, and if the verification is successful, calculate R = V+R0U1mod Q.

The revocation protocol is actually a blind signature protocol. A signature Sign(A, B)=(z, a, b, r) is valid if and only if gr = yH0 (A‖B‖z‖a‖b)a and ar = zh0 (a ‖. The electronic cash obtained by users is Coin = {A, b, Sign(A, B)}.

Extended data:

The essence of electronic cash

Independence: the security of electronic cash can not be guaranteed only by physical security, but also by various cryptographic technologies used by electronic cash itself;

2. Non-repetitive expenses: Electronic cash can only be used once, and repetitive expenses can be easily detected;

3. Anonymity: banks and merchants can't track the use of electronic cash, that is, they can't link the purchase behavior of electronic cash users, thus hiding the purchase history of electronic cash users;

4. unforgeability: users can't make counterfeit money, including two situations: first, users can't make effective electronic cash out of thin air; Second, after users withdraw n effective electronic cash from the bank, they can't make effective electronic cash according to the withdrawal and payment information of these n electronic cash;

5. Transitivity: users can transfer electronic cash between users at will like ordinary cash and cannot be tracked;

6. Separability: Electronic cash can not only be used as a whole, but also be divided into smaller parts for multiple use. As long as the sum of the denominations of each part is equal to the original electronic cash, any amount can be paid;

Baidu encyclopedia-electronic cash