// specify the requested range.
func DecryptSinglePart(w io.Writer, offset, length int64, key ObjectKey) io.WriteCloser {
	const PayloadSize = 1 << 16 // DARE 2.0
	w = ioutil.LimitedWriter(w, offset%PayloadSize, length)

	decWriter, err := sio.DecryptWriter(w, sio.Config{Key: key[:]})
	if err != nil {
		logger.CriticalIf(context.Background(), errors.New("Unable to decrypt io.Writer using object key"))