Secure Sockets Layer (SSL)
The Secure Sockets Layer (SSL) is a protocol widely used on the Internet to secure transmitted messages. The successor to SSL is Transport Layer Security (TLS), which is based on SSL. SSL resides programmatically between the Hypertext Transfer Protocol (HTTP) for the Internet and the Transport Control Protocol (TCP). It is built into Microsoft and Netscape browsers and most web servers. Developed by Netscape, SSL was soon endorsed by Microsoft and other Internet client and server developers. SSL was considered the de facto standard until it was further developed into Transport Layer Security. The word "socket" in the term refers to the sockets' usual method of exchanging data: data can be moved back and forth between client and server programs on a network or between the program layers of a single computer . SSL uses the public/private key encryption system developed by RSA. The system also allows the use of a digital certificate.
TLS and SSL are a core part of most web browsers (clients) and web servers. If the website is on a server that supports SSL, SSL can be activated. This enables identification of specific websites requesting SSL access. Any web server can be enabled using Netscape's SSLRef library. The program library is available for download for non-commercial use. A license is required for commercial use.
TLS and SSL are not compatible with each other. However, a message sent with TLS can be processed by a client that supports SSL but not TLS.