SSH, or secure shell, is a package used for secure remote access between different machines, replacing the “r” family of utilities. In addition to replacing these SSH allows for secure X11 communication and for forwarding of TCP connections.

SSH is actually composed of two different protocols (and implementations), SSH1 and SSH2, that are incompatible. SSH1 uses both server and host keys for authentication. It uses RSA cipher for authentication. SSH2 uses only host keys, and authentication is done using DSA.

SSH Communications Security maintains secure shell protocol and ssh1 and 2 releases. The secure shell standard is vendor neutral. Several releases exist, mostly share/freeware or GPL equivalents. The OpenSSH project, part of the OpenBSD project offers free software releases of high quality for different platforms.

SSH FAQ is available on the net.

The ideal situation described herein is not exact. SSH Communications Security and the freeware market don't always follow the exact same protocol and this may cause problems.

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