China Bank's electronic cash, in layman's terms, is an electronic wallet account superimposed on your bank card. You can choose to pay by bank card account or electronic cash account when you swipe your card. The advantage of electronic cash is that it is fast to pay. Just like swiping a bank card and a bus card, it can be put on a POS machine, which saves the trouble of change. \x0d\ Electronic cash is a technology to simulate cash in electronic form. E-cash system attempts to copy the characteristics of cash online transactions in many aspects: convenience, low cost (or no transaction cost); E-cash is regarded as cash, and the account limit is 1000 yuan. Like cash, it is anonymous and does not report the loss. In other words, if your card is lost, you can reissue it. The money in the bank account is reserved, but the money in the electronic cash can't be recovered, just like if you lose your wallet, the cash in it can't be recovered. \ x0d \: \ x0d \ Electronic cash, also known as electronic money or digital currency (di electronic cash flow), is a very important electronic payment system, which can be regarded as an electronic or digital simulation of real money. Electronic cash exists in the form of digital information and circulates through the Internet. But it is more convenient and economical than real money. Its simplest form includes three subjects: merchants, users and banks; And four security protocol processes: initialization protocol, withdrawal protocol, payment protocol and deposit protocol. \x0d\ The first electronic cash scheme was put forward by Chaum in 1982, and it was realized by blind signature technology, which can completely protect users' privacy. However, this completely anonymous electronic cash has also provided convenience for many criminals, who use its completely anonymity to carry out some illegal and criminal activities, such as corruption and illegal purchases (such as buying drugs and arms). ), extortion and so on. Even if the police get the stolen money, they can't catch the criminal. \x0d\ Therefore, a reasonable electronic cash system should be incomplete or conditionally anonymous. In 1995, Stadhle and others put forward the concept of fair blind signature, which can be used in conditional anonymous payment system. \x0d\ 1996, Camenisch et al. and Frankel et al. independently put forward the concept of fair off-line electronic cash for the first time, and gave two schemes at the same time. The anonymity of users in fair electronic cash is incomplete, and it can be revoked by a trusted third party (TTP), thus using the complete anonymity of electronic cash to prevent criminal activities.