rc;

       rc = gnutls_session_channel_binding (session,
                                            GNUTLS_CB_TLS_UNIQUE,
                                            &cb);
       if (rc)
         fprintf (stderr, "Channel binding error: %s\n",
                  gnutls_strerror (rc));
       else
         {
           size_t i;
           printf ("- Channel binding 'tls-unique': ");
           for (i = 0; i < cb.size; i++)
             printf ("%02x", cb.data[i]);
           printf ("\n");
         }
     }