private static byte[] lmv2Response(byte[] hash, byte[] clientData,
            byte[] challenge) throws Exception {
        byte[] data = new byte[challenge.length + clientData.length];
        System.arraycopy(challenge, 0, data, 0, challenge.length);
        System.arraycopy(clientData, 0, data, challenge.length,
                         clientData.length);
        byte[] mac = hmacMD5(data, hash);
        byte[] lmv2Response = new byte[mac.length + clientData.length];
        System.arraycopy(mac, 0, lmv2Response, 0, mac.length);
        System.arraycopy(clientData, 0, lmv2Response, mac.length,
                         clientData.length);
        return lmv2Response;
    }