+.Ss SSH protocol version 2
+.Pp
+When a user connects using the protocol version 2
+different authentication methods are available:
+At first, the client attempts to authenticate using the public key method.
+If this method fails password authentication is tried.
+.Pp
+The public key method is similar to RSA authentication described
+in the previous section except that the DSA algorithm is used
+instead of the patented RSA algorithm.
+The client uses his private DSA key
+.Pa $HOME/.ssh/id_dsa
+to sign the session identifier and sends the result to the server.
+The server checks whether the matching public key is listed in
+.Pa $HOME/.ssh/authorized_keys2
+and grants access if both the key is found and the signature is correct.
+The session identifier is derived from a shared Diffie-Hellman value
+and is only known to the client and the server.
+.Pp
+If public key authentication fails or is not available a password
+can be sent encrypted to the remote host for proving the user's identity.
+This protocol 2 implementation does not yet support Kerberos or
+S/Key authentication.
+.Pp
+Protocol 2 provides additional mechanisms for confidentiality
+(the traffic is encrypted using 3DES, Blowfish, CAST128 or Arcfour)
+and integrity (hmac-sha1, hmac-md5).
+Note that protocol 1 lacks a strong mechanism for ensuring the
+integrity of the connection.
+.Pp
+.Ss Login session and remote execution
+.Pp