Secure Sockets Layer (SSL), developed by Netscape Communications, and Transport Layer Security (TLS), the open-standard replacement for SSL from the Internet Engineering Task Force, are the two protocols that add encryption and authentication to TCP/IP. This article summarizes the basic concepts of how the two protocols work and how Apache implements these protocols so that one can transmit information securely over HTTP. A short and interesting read for the tech junkies out there: "O'Reilly Network: Apache and SSL".