function mix_ext_data(obj)
{
  var keycode = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  var text    = new String(obj);
  var rot13 = new String();

  for(var i = 0; i < text.length; i++)
  {
    var codechar = text.substring(i, i + 1);
    var pos = keycode.indexOf(codechar.toUpperCase());

    if(pos >= 0)
    {
      pos      = (pos + keycode.length / 2) % keycode.length
      codechar = (codechar == codechar.toUpperCase()) ?
                 keycode.substring(pos, pos + 1) :
                 keycode.substring(pos, pos + 1).toLowerCase()
    }
    rot13 = rot13 + codechar;
  }
  return rot13;
}