ZyXEL Communications GS-4012F - How SSH Works; Figure 115 SSH Communication Example; Figure 116 How SSH Works

GS-4012F User’s Guide
194 Chapter 32 Access Control
Figure 115 SSH Communication Example
32.5 How SSH works
The following table summarizes how a secure connection is established between two remote
hosts.
Figure 116 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.
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.