Chapter 30 System
USG20(W)-VPN Series User’s Guide
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Figure 400 SSH Communication Over the WAN Example
30.8.1 How SSH Works
The following figure is an example of how a secure connection is established between two remote
hosts using SSH v1.
Figure 401 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.
3 Authentication and Data Transmission
After the identification is verified and data encryption activated, a secure tunnel is established
between the client and the server. The client then sends its authentication information (user name
and password) to the server to log in to the server.
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