Secure Shell (SSH)#
SSH, short for secure shell, is network protocol using strong cryptography to protect traffic in untrusted networks. Its original use is to provide access to a shell on a remote system in secure manner. But many more applications are possible, like transmitting files or more generally providing a secure channel for any otherwise unprotected network traffic.
With respect to SSH there are two instances the SSH client and the SSH server. The server program constantly running on a remote machine, possibly a D-PHYS server, waiting for incoming connections. The client is program executed in an ad-hoc fashion to initiate and use an SSH secure channel.