In Greek myth, the three-headed dog Kerberos guarded the gates of Hades. These days, Kerberos is an authentication service developed at MIT for open network computing environments such as MITnet. Kerberos verifies that you are who you claim to be by matching your username and password, called a Kerberos principal, to a private key encryption.
When you start an application that relies on Kerberos authentication, you must identify yourself by giving your Kerberos principal. The Kerberos service checks to make sure that your name and password match the encrypted key before it gives you access to the service you have requested. The security of the network environment is maintained by never sending your unencrypted Kerberos password over the network.
To use the Athena system, you must have a Kerberos username and password. Some Macintosh and Windows applications at MIT that use Kerberos to authenticate a user's identity are Eudora, Zephyr and AFS.
See Also
An Authentication Service for Open Network Systems
(This technical description of Kerberos, by Steiner, Neuman, and Schiller, is available via anonymous ftp from athena-dist.mit.edu, /pub/kerberos/doc/usenix.txt.)
Kerberos: How Does the Other Guy Know Who I Am?.
(This basic introduction to Kerberos and definitions of Kerberos-related terms is available in the SIPB publication An Inessential Guide to Athena.)