OpenSSH is a free, open source implementation of the SSH (Secure Shell) protocols. It replaces telnet, ftp, rlogin, rsh, and rcp with secure, encrypted network connectivity tools. OpenSSH supports versions 1.3, 1.5, and 2 of the SSH protocol. Since OpenSSH version 2.9, the default protocol is version 2, which uses RSA keys as the default.
It is strongly recommended to use OpenSSH to remotely login into the system.