3Com 3C13636 Configuration Manual page 213

3Com Router 3000 Ethernet Family
Configuration Guide
Thus, the server and the client obtain the same session key. During the session, both
ends use the same session key to perform encryption and decryption, thereby
guaranteeing the security of data transfer.
3) Authentication mode negotiation
The client sends its username information to the server.
The server initiates a process to authenticate the user. If the user needs no
authentication, the server proceeds to session request phase directly.
The client adopts an authentication mode to authenticate the server till the
authentication succeeds or the server tears down the connection because of
timeout.
Note:
SSH provides two authentication modes: password and RSA.
1) Password authentication procedure
The client sends the username and password to the server.
The server compares the received username and password with the local
configuration. If it finds an exact match, the authentication succeeds.
2) RSA authentication procedure
The server configures the RSA public key of the client.
The client sends its RSA public key member modulo to the server.
The server verifies the member modulo. If the member modulo is valid, the server
generates a random number, encrypts it using the RSA public key from the client,
and sends the encrypted information back to the client.
The server and the client use the random number and the session ID as parameters
to calculate authentication data.
The client sends the authentication data it generated to the server.
The server compares the received authentication data with that locally calculated. If
they match, the authentication succeeds.
4) Session request: If the authentication succeeds, the client sends a session
request to the server. When the server has successfully processed the request,
SSH enters the interactive session phase.
5) Interactive session: The client and the server exchange data till the session is
over.
11.6.2 SSH Configuration
SSH configuration includes:
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Chapter 11 Terminal Services