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6
User Authentication
d. The client uses its private key to decrypt the challenge string, computes the
MD5 checksum, and sends the checksum back to the switch.
e. The switch compares the checksum sent from the client against that
computed for the original string it sent. If the two checksums match, this
means that the client's private key corresponds to an authorized public key,
and the client is authenticated.
Authenticating SSH v2 Clients
a. The client first queries the switch to determine if DSA public key
authentication using a preferred algorithm is acceptable.
b. If the specified algorithm is supported by the switch, it notifies the client to
proceed with the authentication process. Otherwise, it rejects the request.
c. The client sends a signature generated using the private key to the switch.
d. When the server receives this message, it checks whether the supplied key
is acceptable for authentication, and if so, it then checks whether the
signature is correct. If both checks succeed, the client is authenticated.
Note:
The SSH server supports up to four client sessions. The maximum number of
client sessions includes both current Telnet sessions and SSH sessions.
Generating the Host Key Pair
A host public/private key pair is used to provide secure communications between an
SSH client and the switch. After generating this key pair, you must provide the host
public key to SSH clients and import the client's public key to the switch as
described in the preceding section (Command Usage).
Field Attributes
• Public-Key of Host-Key – The public key for the host.
- RSA: The first field indicates the size of the host key (e.g., 1024), the second
field is the encoded public exponent (e.g., 65537), and the last string is the
encoded modulus.
- DSA: The first field indicates that the encryption method used by SSH is based
on the Digital Signature Standard (DSS). The last string is the encoded modulus.
• Host-Key Type – The key type used to generate the host key pair (i.e., public and
private keys). (Range: RSA, DSA, Both: Default: Both)
The SSH server uses RSA or DSA for key exchange when the client first
establishes a connection with the switch, and then negotiates with the client to
select either DES (56-bit) or 3DES (168-bit) for data encryption.
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