Central Authentication Service is a web oriented Single Sign On system. It was created in the early 2000s at Yale University. In 2004, CAS came under the banner of special interest group Jasig.
CAS provides for Single Sign On between multiple sites, including on different domains, by means of one-time password tokens. The applications themselves never have access to the user’s password, but rather log in the user after querying CAS. The communication protocol used is SAML v2 and, in later versions of CAS, additional information can be transmitted at user login (groups, full name, etc.). CAS can use different types of back ends as the user database, such as an LDAP directory, a relational database, flat files and so on. CAS also supplies a proxy system that allows an application to transfer the user’s identification to another back end application (whether web based or not), such as a web service or an IMAP server.
CAS is distributed under the Jasig (BSD-style) License.
CAS is written in Java and supplies CAS clients for SSO integration with applications, in Java, PHP and .NET. An Apache module is also available.
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