25.1 About OpenSSH

OpenSSH is suite of network connectivity tools that provides secure communications between systems, including:

scp

Secure file copying.

sftp

Secure File Transfer Protocol (FTP).

ssh

Secure shell to log on to or run a command on a remote system.

sshd

Daemon that supports the OpenSSH services.

ssh-keygen

Creates DSA or RSA authentication keys.

Unlike utilities such as rcp, ftp, telnet, rsh, and rlogin, the OpenSSH tools encrypt all network packets between the client and server, including password authentication.

OpenSSH supports SSH protocol version 1 (SSH1) and version 2 (SSH2). In addition, OpenSSH provides a secure way of using graphical applications over a network by using X11 forwarding. It also provides a way to secure otherwise insecure TCP/IP protocols by using port forwarding.