Heimdal is an independently developed and free implementation of the Kerberos 5 protocol, unencumbered by US export restrictions. It is compatible with other implementations and is close to the MIT Kerberos 5 API. It includes versions of common applications such as telnet, ftp, rsh, su, and login. Furthermore, it has some new features not available in other implementations, such as authenticated and encrypted X connections, incremental database propagation, and support for IPv6 and Triple DES . There is also support for operation in firewalled environments.