* @param key the secret key
   * @throws IllegalArgumentException if the given key is inappropriate for initializing this MAC
   * @since 20.0
   */
  public static HashFunction hmacSha1(Key key) {
    return new MacHashFunction("HmacSHA1", key, hmacToString("hmacSha1", key));
  }

  /**
   * Returns a hash function implementing the Message Authentication Code (MAC) algorithm, using the

                (byte) 0x99 };

        byte[] output = new byte[12];
        byte[] dk = deriveKeyAES(baseKey, cst); // Checksum key
        try {
            Mac m = Mac.getInstance("HmacSHA1");
            m.init(new SecretKeySpec(dk, HMAC_KEY));
            System.arraycopy(m.doFinal(input), 0, output, 0, 12);
            return output;
        } finally {