ZyXEL Communications ZyXEL Dimension ES-2724, User Manual, Page: 203 / 341

ES-2724 User’s Guide
Chapter 30 Access Control 201
Figure 105 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.
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.
30.6 SSH Implementation on the Switch
Your switch supports SSH version 2 using RSA authentication and three encryption methods
(DES, 3DES and Blowfish). The SSH server is implemented on the switch for remote
management and file transfer on port 22. Only one SSH connection is allowed at a time.