Kerberos 5 is a network authentication and single sign-on system. Heimdal is a free Kerberos 5 implementation without export restrictions written from the spec including advanced features like thread safety, IPv6, master-slave replication of Kerberos Key Distribution Center server and support for ticket delegation . This package can coexist with MIT Kerberos 5 packages. Hesiod is disabled by default since it is deemed too big a security risk by the packager.