"While a properly set up SSH service can give you secure remote
access to a server, you might not like the idea of having an SSH
server always running on your machine. Secure Back Door (SBD) can
open an encrypted connection to your system, allowing you to
remotely execute any operating system commands for example start
your SSH or Web server or reboot the server.
"SBD can listen on any port you like. If you don't specify a
port it will default to port 31415. The transport protocol is SBD,
which is based on a one-time pad symmetric key and a keyed-hash
message authentication code (HMAC), which verify data integrity and
the authenticity of a message..."