SSH was primarily designed to enable a user to securely log on to a remote computer and perform shell and network services. For example, it could be used by network administrators logging into a remote Web server. It is also considered a secure replacement to the Telnet, RSH and Rexec protocols. Typically, SSH-based communications/processes work on a client/server architecture consisting of a client and server SSH. The client is securely authenticated and connected, and sends encrypted commands to be executed on the server. Both the client and server are authenticated using RSA public key cryptography based digital certificates. SSH uses AES, IDEA and Blowfish as the encryption algorithms.