Authorization software that makes use of private-key authentication. Developed by the Massachusetts Institute of Technology (MIT), Kerberos is available for free, although commercial versions exist. Kerberos was named for the three-headed dog, also known as Cerberus, that guarded the gates of Hades in Greek mythology. Note: Although, according to Greek legend, Hercules defeated Kerberos, a hacker of Herculean proportions has yet to emerge victorious over this powerful security software. See also Access Manager, authorization, security, and Sesame.