cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(keybytes, "AES"), new IvParameterSpec(ZERO_IV, 0, ZERO_IV.length));
        if ( constant.length != cipher.getBlockSize() ) {
            constant = expandNFold(constant, cipher.getBlockSize());
        }
        byte[] enc = constant;
        int klen = keybytes.length;
        byte[] dk = new byte[klen];
        for ( int n = 0; n < klen; ) {

        }
    }


    private static void verifyNfold ( int n, String string, String expect ) {
        byte[] expanded = PacMac.expandNFold(string.getBytes(StandardCharsets.US_ASCII), n / 8);
        Assert.assertEquals(expect, Hexdump.toHexString(expanded).toLowerCase(Locale.ROOT));
    }



    @Test