4 ssh overview, 5 how ssh works, 4 ssh overview 29.5 how ssh works – ZyXEL Communications GS-2724 User Manual

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Chapter 29 Access Control

GS-2724 User’s Guide

198

29.4 SSH Overview

Unlike Telnet or FTP, which transmit data in clear text, SSH (Secure Shell) is a secure
communication protocol that combines authentication and data encryption to provide secure
encrypted communication
between two hosts over an unsecured network.

Figure 100 SSH Communication Example

29.5 How SSH works

The following table summarizes how a secure connection is established between two remote
hosts.

Figure 101 How SSH Works

1 Host Identification

The SSH client sends a connection request to the SSH server. The server identifies itself
with a host key. The client encrypts a randomly generated session key with the host key
and server key and sends the result back to the server.