final DerivationParameters param = new KDFCounterParameters(sessionKey, null /* prefix */, suffix /* suffix */, r /* r */);
        gen.init(param);

        final byte[] derived = new byte[16];
        gen.generateBytes(derived, 0, 16);
        return derived;
    }

    /**
     * @param string
     * @return null terminated ASCII bytes
     */
    private static byte[] toCBytes(final String string) {