1. SET is the abbreviation of Secure Electronic Transaction. It is an open electronic payment protocol standard based on electronic money established for online transactions on the Internet. 2. What SET wants to achieve The goals are: to ensure the safe transmission of information on the Internet, to ensure the mutual isolation of e-commerce participant information, to solve multi-party authentication problems, to ensure the real-time nature of online transactions, to promote the compatibility and interoperability of software developed by different manufacturers, and to be able to Runs on different hardware and operating system platforms. 3. The objects involved in the SET protocol specification include consumers, online stores, acquiring banks, electronic currencies and certification centers (CA), etc. 4. The SET protocol mainly uses symmetric encryption , public key encryption, hash algorithm, digital signature technology and public key right mechanism and other technologies. The application of these technologies enables SET to ensure the confidentiality, consistency and integrity of transaction data, and realize the authentication of merchants. Consumers provide a means to authenticate merchant identities, and at the same time promote the compatibility of software developed by different manufacturers, enabling interoperability on different hardware and operating system platforms. In summary, SET has many advantages, so it is said that SET Credit card payment forms represent the development direction of e-commerce payment and settlement.