The following series of events helps protect the integrity of SSH
communication between two hosts.
First, a secure transport layer is created so
that the client knows that it is communicating with the correct
server. Then, the communication is encrypted between the client and
server using a symmetric cipher.
With a secure connection to the server in place, the client
authenticates itself to the server without worrying that the
authentication information may be compromised.
Finally, with the client authenticated to the server, several different
services can be safely and securely used through the connection, such as
an interactive shell session, X11 applications, and tunneled TCP/IP ports.
