* reset.
     *
     * @return the array of bytes for the resulting hash value.
     */
    public byte[] engineDigest () {
        // pad output to 56 mod 64; as RFC1320 puts it: congruent to 448 mod 512
        int bufferNdx = (int)(count % BLOCK_LENGTH);
        int padLen = (bufferNdx < 56) ? (56 - bufferNdx) : (120 - bufferNdx);

        // padding is alwas binary 1 followed by binary 0s