public static String checksum(Client client) {
        String s = buildUniqueString(client);
        if (s == null) {
            return "0";
        }
        return MD5Utils.md5Hex(s, Constants.ENCODE);
    }
@Test
    void performanceTestOfChecksum() {
        long start = System.nanoTime();
        for (int i = 0; i < N; i++) {
            DistroUtils.checksum(client1);
        }
        System.out.printf("Distro Verify Checksum Performance: %.2f ivk/ns\n", ((double) System.nanoTime() - start) / N);
    }