What Is Electronic Cash?

Electronic Cash is actually a technology that simulates cash in electronic form. Electronic cash systems attempt to replicate the characteristics of cash for online transactions in a number of ways: convenience, low fees (or no transaction fees). Anonymous and other properties. But not all electronic cash systems meet these characteristics, and most electronic cash systems can provide quickness and convenience for small online transactions.

E-commerce is a business activity carried out through the Internet. A very critical requirement for e-commerce is to have a secure and efficient electronic cash system. Since D. Chaum [2] published the first paper on electronic cash systems in 1982, many research results have been achieved in the research of electronic cash systems.

Electronic cash (E-cash) full name: Electronic cash. Also known as

Electronic cash exists in the form of digital information and circulates through communication networks. Electronic cash has to go through three processes of withdrawal, payment and deposit in its life cycle, involving users, merchants and banks. The basic circulation mode of electronic cash: users and banks execute withdrawal agreements to withdraw electronic cash from banks; users and merchants execute payment agreements to pay for electronic cash; merchants and banks execute deposit agreements to deposit electronic cash from transactions into banks. ^[1]

The electronic cash system can be divided into account-based electronic cash system and voucher-based electronic cash system according to the carrier of the transaction. According to whether the merchant needs to perform online verification with the bank when the electronic cash is spent, it is divided into online electronic cash system and offline electronic Cash system. According to whether an electronic cash can be legally paid, the electronic cash is divided into a divisible electronic cash and an indivisible electronic cash. ^[1]

E-cash plays the same role as ordinary cash in the economic field and is essential for normal economic operation. Electronic cash should have the following properties: (1) System independence. The use of electronic cash has nothing to do with computer systems. (2) Non-recurring expenses. Electronic cash can only be used once, and recurring expenses can be easily checked. (3) Anonymity. Collusion between banks and merchants cannot track the use of electronic cash. (4) Unforgeability. Users cannot counterfeit coins. There are two cases: one is that the user cannot make valid electronic cash out of thin air; the other is that after the user has withdrawn N valid electronic cash from the bank, he cannot withdraw and pay for the N Electronic cash information creates effective electronic cash. (5) Transferability. Users can lend electronic cash to others like ordinary cash, and cannot be tracked. (6) Dividability. Electronic cash can be paid in any amount. ^[1]

The security and reliability of electronic cash are mainly achieved by cryptographic technologies, mainly including: (1) Segmentation selection technology. When users withdraw electronic cash, they cannot let the bank know the identity information of the user in electronic cash, but the bank needs Know that the e-cash being withdrawn is constructed correctly. The segmentation selection technology is that the user correctly constructs N electronic cash to the bank, and the bank randomly selects N -1 of them to let the user give their structure. If the structure is correct, the bank considers that the other structure is also correct, and Sign it. (2) Zero-knowledge proof. The prover proves to the verifier and believes that he knows or owns a certain message, but the proof process cannot leak any information about the proven message to the verifier. The above two techniques are used to make the user s Identity information is embedded in electronic cash. (3) Authentication. On the one hand, authentication is to verify that the sender of the information in the communication is real and not counterfeit; on the other hand, it is to verify that the transmitted information is correct and complete without being tampered, replayed or delayed. Digital signature. The signature applicant sends the message to be signed to the signer after blind exchange. The signer does not know the specific content of the signed message. This technology is used to realize the anonymity of the user. ^[1]

Electronic cash goes through three processes of withdrawal, payment and deposit in its life cycle, involving users, merchants and banks. The basics of electronic cash

* The electronic cash system can be divided into

Electronic cash plays the same role as ordinary cash in the economic field,

The security and reliability of electronic cash are mainly realized by cryptographic technologies, mainly including:

The basic process of electronic cash design is as follows:

Withdrawal Agreement

1. Withdrawal Protocol: Users withdraw electronic cash from their bank account. In order to guarantee the user's anonymity to obtain legal electronic cash with a bank signature, the user will interact with the bank to perform a blind signing

Offline electronic cash specific plan:

Initialization protocol

(Only executed once)

Bank B selects parameters based on the discrete logarithm problem: select two large prime numbers p, q and q | (p-1). Define the subgroup Gq of order q on the multiplicative group ZP and a generating tuple (g, g 1, g 2) of Gq, the signature of bank B

Research on the usability of electronic cash transferability

Transitivity is a basic feature of physical cash, but it has not been applied in electronic cash. The main reason is that in order to track users who spend repeatedly in electronic cash, blind user identity information is added to electronic cash. In the process of electronic cash flow, the identity information of all users who have used the electronic cash will be added. Therefore, according to the theory of information theory, the length of electronic cash is constantly increasing, and each transaction will cause a large amount of communication problems, which is not beneficial to actual Application; In addition, electronic cash is relatively easy and effective compared to physical cash, whether in the process of construction or deposit. Therefore, the study of fair offline electronic cash does not focus on the transferability of electronic cash.

Research on Multi-bank Electronic Cash

Existing fair electronic cash solutions are all issued by one bank, but in real life, electronic cash issued by multiple electronic banking systems is more suitable than electronic cash issued by a single bank, because in a country or region There may be more than one bank with electronic cash issuance capabilities. These banks form a group, they are managed by the central bank of the country, and each bank can issue electronic cash. Therefore, the fair electronic cash model issued by multiple banks is an important direction of electronic cash system research. The research in this area mainly uses improved

The divisible electronic cash system allows users to make legal and accurate payments multiple times, reducing the number of withdrawals, which can reduce network communication and improve system efficiency. Therefore, the divisible electronic cash system is the focus of research. Okamoto and Ohta first proposed a divisible electronic cash system in 1991, which allows users to divide electronic cash into any amount and make multiple payments until it is equal to the total amount of the electronic cash. In order to enable banks to effectively detect users' repeated payments, they have adopted binary tree technology to represent electronic cash. However, this technology has led to large amounts of communication, high computational complexity, and low efficiency in electronic cash payment protocols. The schemes have proposed improvements from different perspectives [6-10], but the implementation efficiency of payment protocols is still very low due to the use of binary tree representations. Therefore, so far, the divisible electronic cash system is still impractical. In this regard, it is also possible to introduce a trusted third party to realize the identification of overpayers, so that the electronic cash payment agreement does not need to include the information of double payment check, so that the binary tree representation technology of divisible electronic cash can be abandoned , Thereby constructing a simpler separable electronic cash system.