Information is now the most valuable resource in the world. Whether it is a personal letter or an industrial secret, all information has a worth to someone. This thesis considers issues of security and privacy for such information. It discusses the reasons for wishing to protect data and the methods available for doing so. Specifically, the project concerns cryptography and secure communications, in particular the Secure Sockets Layer (SSL) protocol. It contains a communications and security analysis of SSL as well as details of the construction of a secure reference implementation of the protocol.