4 ssh overview, 5 how ssh works, 4 ssh overview 33.5 how ssh works – ZyXEL Communications ZyXEL Dimension GS-4012F User Manual

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Chapter 33 Access Control

33.4 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 128 SSH Communication Example

33.5 How SSH works

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

Figure 129 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.