Ssh; How Ssh Works; Figure 335 Ssh Communication Example; Figure 336 How Ssh V1 Works Example - ZyXEL Communications ZyWALL 1050 User Manual

35.6 SSH

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 335 SSH Communication Example

35.6.1 How SSH Works

The following figure is an example of how a secure connection is established between two
remote hosts using SSH v1.

Figure 336 How SSH v1 Works Example

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.
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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