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SSH Terminal Service 313

3 Authentication mode negotiation:

■ The client sends its username information to the server.

■ The server initiates a procedure to authenticate the user. If the server is

configured not to authenticate the user, the process proceeds to session

request phase directly.

■ The client employs an authentication mode to authenticate the server till the

authentication succeeds or the server tears down the connection because of

timeout.

SSH provides two authentication modes: password authentication and RSA

authentication.

■ Password authentication procedure:

■ The client sends the username and password to the server;

■ The server compares the username and password sent from the client with

the local configuration. If it finds an exact match, the authentication

succeeds.

■ RSA authentication procedure:

■ The server configures an RSA public key for the client;

■ The client sends its RSA public key member module to the server;

■ The server performs validity authentication on the member module. If the

authentication succeeds, 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;

■ Both the server and the client uses the random number and the session ID

as parameters to calculate the authentication data;

■ The client sends the authentication data it generates to the server;

■ The server compares the authentication data from the client 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.

3Com Switch 4500 26-Port User Manual

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