Ssh Overview; How Ssh Works - ZyXEL Communications VES1724-56 User Manual

Chapter 38 Access Control

38.4 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 204 SSH Communication Example

38.5 How SSH works

The following table summarizes how a secure connection is established between two remote hosts.
Figure 205 How SSH Works
Host Identification
1
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.
The client automatically saves any new server public keys. In subsequent connections, the server
public key is checked against the saved version on the client computer.
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