CAS is a single sign-on protocol. The official specification introduces it as follows:
"The Central Authentication Service (CAS) is a single-sign-on / single-sign-off protocol for the web. It permits a user to access multiple applications while providing their credentials (such as userid and password) only once to a central CAS Server application."
Liferay provides ready-to-use functionality based on JASIG CAS (CAS became a Java in Administration Special Interest Group (JASIG) project in December 2004 and is now also known as JASIG CAS). In many projects, especially internal ones (for instance, intranet) it is necessary to provide single sign-on. CAS integrates with the following authentication mechanisms: