length of 8 bytes (64 bits). This length was chosen because some faulty implementations
  require different lengths of the padding string, but not more than 8 bytes. Thus the position of the hash identifier (HI) and the hash digest (HD) are also fixed.
  </li>
  <li>
  The appended garbage does not need to be calculated, but consists simply of appended bytes with the value 'FF'.</li>
</ul>

The Kuehn approach works like this: The cube root of the structure described above is extracted. Then the integer part