SSL protocol is an encryption protocol developed by Netscape in 1994. It was called Secure Sockets Layer, and was later taken over by IETF, the Internet Engineering Task Force, and renamed as TLS protocol. SSL/TLS protocol is widely used in data encryption and identity authentication between Web browser and Web server: encrypting communication data to prevent information from being leaked or tampered during transmission, and authenticating the communication party to ensure that the information comes from the right party. Generally speaking, SSL protocol was born to protect the security of information and data transmitted between users and websites.

SET protocol is an agreement developed by MasterCard and Visa in cooperation with Netscape, Microsoft and other companies in June 1997. It is called secure electronic transaction protocol, which ensures the security of information and data when users use credit cards to conduct transactions on the Internet.

The common point is that public key cryptosystem and X.509 digital certificate standard are used for data encryption and authentication, but the difference is that SET is mainly used for B2C, while SSL is used for communication between all web browsers and web servers.