Electronic cash-based offline transaction method and system

An electronic cash-based offline transaction method, comprising:

• receiving, by a back-end server from a smart card, an anti-replay factor generated by the smart card;
• determining, by the back-end server in accordance with a predetermined algorithm, whether an abnormal transaction occurs on the smart card, generating, by the back-end server when no abnormal transaction occurs, a security information signature by signing security information with a private key of the back-end server, and transmitting, by the back-end server, the security information and the security information signature to the smart card, wherein the security information at least comprises an anti-replay factor and active field information, and the active field information at least comprises a term of validity of the smart card and a tradable currency of the smart card;
• receiving, by the smart card, the security information and the security information signature from the back-end server, performing a signature verification, by the smart card, on the security information signature by using a public key of the back-end server, determining, by the smart card after the signature verification succeeds, whether the anti-replay factor in the security information is consistent with the anti-replay factor generated by the smart card, and storing, by the smart card, the active field information, when the anti-replay factor in the security information is consistent with the anti-replay factor generated by the smart card;
• establishing, by a transaction terminal, a connection with the smart card, and transmitting, by the transaction terminal, application selection information of an electronic cash transaction to the smart card, when no connection is established between the transaction terminal and the back-end server;
• receiving, by the smart card, the application selection information of the electronic cash transaction, determining, by the smart card, that an application for the electronic cash transaction is activated, and transmitting, by the smart card, the active field information to the transaction terminal, when no connection is established between the smart card and the back-end server;
• generating, by the transaction terminal, transaction information, and determining, by the transaction terminal, whether the active field information is in a valid state, wherein the transaction information at least comprises the transaction amount, transaction time and a currency type identifier, wherein the determining whether the active field information is in the valid state comprises:
• determining that the active field information is in the valid state in response to the transaction time in the transaction information being within the term of validity of the smart card in the active field information and transaction currency corresponding to the currency type identifier in the transaction information being the tradable currency of the smart card in the active field information;
• terminating a transaction process, when the active field information is invalid;
• transmitting the transaction information to the smart card, when the active field information is valid;
• deducting, by the smart card after receiving the transaction information, the transaction amount in the transaction information from a balance in the smart card, obtaining, by the smart card, a transaction receipt by calculating the transaction information, and transmitting, by the smart card, the transaction receipt to the transaction terminal;
• and
• establishing, by the smart card, the connection with the back-end server, generating, by the smart card, the anti-replay factor, and transmitting, by the smart card, the anti-replay factor to the back-end server.