ZyXEL Communications USG60W - How SSH Works

Chapter 44 System
ZyWALL USG Series User’s Guide
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Figure 667 SSH Communication Over the WAN Example
44.8.1 How SSH Works
The following figure is an example of how a secure connection is established between two remote hosts
using SSH v1.
Figure 668 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.
2 Encryption Method
Once the identification is verified, both the client and server must agree on the type of encryption
method to use.