Números radomicos MD5

RandomGUID.java

public class RandomGUID extends Object {

    private static Random random;
    private static SecureRandom secureRandom;
    private static String secureId;

    /*
     * <pre></b>Bloco estatico para cuidar do tempo de uma parte secureRandom. Este bloco
     * sera executado apenas uma vez por instancia de JVM.</b></pre>
     */
    static {
        secureRandom = new SecureRandom();
        long secureInitializer = secureRandom.nextLong();
        random = new Random(secureInitializer);
        try {
            secureId = InetAddress.getLocalHost().toString();
        } catch (UnknownHostException e) {
            e.getMessage();
        }
    }


    /*
     * <pre><b>Metodo para gerar o GUID aleatorio para converter para o formato padrao
     * para GUID (Util para UniqueIdentifiers de bancos de dados, etc...)
     * Exemplo: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6. Definir secure = true:
     * verdadeiro permite que cada numero aleatorio gerado seja criptografado.
     * Definir secure = false(Default) permite o numero aleatorio padrao seja
     * cripatografado.</b></pre>
     */
    private static String getRandomGUID(boolean secure) throws NoSuchAlgorithmException {
        MessageDigest md5 = null;
        StringBuilder sbValueBeforeMD5 = new StringBuilder();
        md5 = MessageDigest.getInstance("MD5");
        long time = System.currentTimeMillis();
        long rand = 0;
        if (secure) {
            rand = secureRandom.nextLong();
        } else {
            rand = random.nextLong();
        }

        sbValueBeforeMD5.append(secureId);
        sbValueBeforeMD5.append(":");
        sbValueBeforeMD5.append(Long.toString(time));
        sbValueBeforeMD5.append(":");
        sbValueBeforeMD5.append(Long.toString(rand));

        String valueBeforeMD5 = sbValueBeforeMD5.toString();
        md5.update(valueBeforeMD5.getBytes());

        byte[] array = md5.digest();
        StringBuilder sb = new StringBuilder();
        for (int j = 0; j < array.length; ++j) {
            int b = array[j] & 0xFF;
            if (b < 0x10) {
                sb.append('0');
            }
            sb.append(Integer.toHexString(b));
        }
        return sb.toString();
    }

    /**
     * <b>Este método retorna um GUID com 32 caracteres formatados.</b>
     * 
     * @return String
     * @throws java.security.NoSuchAlgorithmException
     */
    public static String get() throws NoSuchAlgorithmException {
        String randomGuid = getRandomGUID(false).toUpperCase();
        StringBuilder sb = new StringBuilder();
        sb.append(randomGuid.substring(0, 8));
        sb.append("-");
        sb.append(randomGuid.substring(8, 12));
        sb.append("-");
        sb.append(randomGuid.substring(12, 16));
        sb.append("-");
        sb.append(randomGuid.substring(16, 20));
        sb.append("-");
        sb.append(randomGuid.substring(20));
        return sb.toString();
    }

    public static void main(String args[]) throws NoSuchAlgorithmException {
        System.out.println(get());
    }
}