Client                                                Server
    ------                                                ------
    Generates ephemeral key pair.
    Calls GSS_Init_sec_context().
    SSH_MSG_KEXGSS_INIT  --------------->

                                           Verifies received key.
(Optional)                  <------------- SSH_MSG_KEXGSS_HOSTKEY

(Loop)
|                                 Calls GSS_Accept_sec_context().
|                           <------------ SSH_MSG_KEXGSS_CONTINUE
|   Calls GSS_Init_sec_context().
|   SSH_MSG_KEXGSS_CONTINUE ------------>

                                  Calls GSS_Accept_sec_context().
                                    Generates ephemeral key pair.
                                          Computes shared secret.
                                                 Computes hash H.
                                     Calls GSS_GetMIC( H ) = MIC.
                            <------------ SSH_MSG_KEXGSS_COMPLETE

    Verifies received key.
    Computes shared secret.
    Computes hash H.
    Calls GSS_VerifyMIC( MIC, H ).