@Override
  public void verifyMac(byte[] mac, byte[] data) throws GeneralSecurityException {
    if (!Bytes.equal(computeMac(data), mac)) {
      throw new GeneralSecurityException("invalid MAC");
    }
  }
Creates an object implementing the {@link Mac} interface using an Hmac underneath.
java_src/src/main/java/com/google/crypto/tink/subtle/PrfMac.java