MD5代码

/* * RandomGUID from http://www.javaexchange.com/aboutRandomGUID.html * @version 1.2.1 11/05/02 * @author Marc A. Mnich * * From www.JavaExchange.com, Open Software licensing * * 11/05/02 -- Performance enhancement from Mike Dubman.   *             Moved InetAddr.getLocal to static block.  Mike has measured *             a 10 fold improvement in run time. * 01/29/02 -- Bug fix: Improper seeding of nonsecure Random object *             caused duplicate GUIDs to be produced.  Random object *             is now only created once per JVM. * 01/19/02 -- Modified random seeding and added new constructor *             to allow secure random feature. * 01/14/02 -- Added random function seeding with JVM run time * */import java.net.InetAddress;import java.net.UnknownHostException;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.security.SecureRandom;import java.util.Random;/* * In the multitude of java GUID generators, I found none that * guaranteed randomness.  GUIDs are guaranteed to be globally unique * by using ethernet MACs, IP addresses, time elements, and sequential * numbers.  GUIDs are not expected to be random and most often are * easy/possible to guess given a sample from a given generator. * SQL Server, for example generates GUID that are unique but * sequencial within a given instance. * * GUIDs can be used as security devices to hide things such as * files within a filesystem where listings are unavailable (e.g. files * that are served up from a Web server with indexing turned off). * This may be desireable in cases where standard authentication is not * appropriate. In this scenario, the RandomGUIDs are used as directories. * Another example is the use of GUIDs for primary keys in a database * where you want to ensure that the keys are secret.  Random GUIDs can * then be used in a URL to prevent hackers (or users) from accessing * records by guessing or simply by incrementing sequential numbers. * * There are many other possiblities of using GUIDs in the realm of * security and encryption where the element of randomness is important. * This class was written for these purposes but can also be used as a * general purpose GUID generator as well. * * RandomGUID generates truly random GUIDs by using the system's * IP address (name/IP), system time in milliseconds (as an integer), * and a very large random number joined together in a single String * that is passed through an MD5 hash.  The IP address and system time * make the MD5 seed globally unique and the random number guarantees * that the generated GUIDs will have no discernable pattern and * cannot be guessed given any number of previously generated GUIDs. * It is generally not possible to access the seed information (IP, time, * random number) from the resulting GUIDs as the MD5 hash algorithm * provides one way encryption. * * ----> Security of RandomGUID: <----- * RandomGUID can be called one of two ways -- with the basic java Random * number generator or a cryptographically strong random generator * (SecureRandom).  The choice is offered because the secure random * generator takes about 3.5 times longer to generate its random numbers * and this performance hit may not be worth the added security * especially considering the basic generator is seeded with a * cryptographically strong random seed. * * Seeding the basic generator in this way effectively decouples * the random numbers from the time component making it virtually impossible * to predict the random number component even if one had absolute knowledge * of the System time.  Thanks to Ashutosh Narhari for the suggestion * of using the static method to prime the basic random generator. * * Using the secure random option, this class compies with the statistical * random number generator tests specified in FIPS 140-2, Security * Requirements for Cryptographic Modules, secition 4.9.1. * * I converted all the pieces of the seed to a String before handing * it over to the MD5 hash so that you could print it out to make * sure it contains the data you expect to see and to give a nice * warm fuzzy.  If you need better performance, you may want to stick * to byte[] arrays. * * I believe that it is important that the algorithm for * generating random GUIDs be open for inspection and modification. * This class is free for all uses. * * * - Marc */public class RandomGUID extends Object {    public String valueBeforeMD5 = "";    public String valueAfterMD5 = "";    private static Random myRand;    private static SecureRandom mySecureRand;    private static String s_id;    /*     * Static block to take care of one time secureRandom seed.     * It takes a few seconds to initialize SecureRandom.  You might     * want to consider removing this static block or replacing     * it with a "time since first loaded" seed to reduce this time.     * This block will run only once per JVM instance.     */    static {        mySecureRand = new SecureRandom();        long secureInitializer = mySecureRand.nextLong();        System.out.println("secureInitializer:"+secureInitializer);        myRand = new Random(secureInitializer);        try {            s_id = InetAddress.getLocalHost().toString();            System.out.println("s_id:"+s_id);        } catch (UnknownHostException e) {            e.printStackTrace();        }    }    /*     * Default constructor.  With no specification of security option,     * this constructor defaults to lower security, high performance.     */    public RandomGUID() {        getRandomGUID(false);    }    /*     * Constructor with security option.  Setting secure true     * enables each random number generated to be cryptographically     * strong.  Secure false defaults to the standard Random function seeded     * with a single cryptographically strong random number.     */    public RandomGUID(boolean secure) {        getRandomGUID(secure);    }    /*     * Method to generate the random GUID     */    private void getRandomGUID(boolean secure) {        MessageDigest md5 = null;        StringBuffer sbValueBeforeMD5 = new StringBuffer();        try {            md5 = MessageDigest.getInstance("MD5");//返回实现指定摘要算法的 MessageDigest 对象。            System.out.println("MD5: " + md5);        } catch (NoSuchAlgorithmException e) {            System.out.println("Error: " + e);        }        try {            long time = System.currentTimeMillis();            System.out.println("time:"+time);            long rand = 0;            if (secure) {                rand = mySecureRand.nextLong();            } else {                rand = myRand.nextLong();            }            // This StringBuffer can be a long as you need; the MD5            // hash will always return 128 bits.  You can change            // the seed to include anything you want here.            // You could even stream a file through the MD5 making            // the odds of guessing it at least as great as that            // of guessing the contents of the file!            sbValueBeforeMD5.append(s_id);            sbValueBeforeMD5.append(":");            sbValueBeforeMD5.append(Long.toString(time));            sbValueBeforeMD5.append(":");            sbValueBeforeMD5.append(Long.toString(rand));            valueBeforeMD5 = sbValueBeforeMD5.toString();                        System.out.println("valueBeforeMD5:" + valueBeforeMD5);            md5.update(valueBeforeMD5.getBytes()); //用指定的字节数组修改该摘要            byte[] array = md5.digest(); //通过执行最后的诸如填充的操作完成散列码的计算。 在调用之后复位该摘要            StringBuffer sb = new StringBuffer();            for (int j = 0; j < array.length; ++j) {                int b = array[j] & 0xFF;                if (b < 0x10) sb.append('0');                sb.append(Integer.toHexString(b));            }            System.out.println("sb:" + sb);            valueAfterMD5 = sb.toString();        } catch (Exception e) {            System.out.println("Error:" + e);        }    }    /*     * Convert to the standard format for GUID     * (Useful for SQL Server UniqueIdentifiers, etc.)     * Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6     */    public String toString() {        String raw = valueAfterMD5.toUpperCase();        System.out.println("raw:" + raw);        StringBuffer sb = new StringBuffer();        sb.append(raw.substring(0, 8));        sb.append("-");        sb.append(raw.substring(8, 12));        sb.append("-");        sb.append(raw.substring(12, 16));        sb.append("-");        sb.append(raw.substring(16, 20));        sb.append("-");        sb.append(raw.substring(20));        return sb.toString();    }    /*     * Demonstraton and self test of class     */    public static void main(String args[]) {        for (int i=0; i< 2; i++) {            RandomGUID myGUID = new RandomGUID();            System.out.println("Seeding String=" + myGUID.valueBeforeMD5);            System.out.println("rawGUID=" + myGUID.valueAfterMD5);            System.out.println("RandomGUID=" + myGUID.toString());        }    }}

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import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * MD5加密
 *
 */
public class MD5Utils {
    /** * 工具类使用的protected构造方法. */
    protected MD5Utils() {
    }

    /**
     * 为字符串生成md5摘要.
     *
     * @param s 输入字符串
     * @return 生成的摘要内容
     * @throws NoSuchAlgorithmException 如果不支持md5算法就抛出异常
     * @throws UnsupportedEncodingException
     */
    public static final String md5(String s)
        throws NoSuchAlgorithmException, UnsupportedEncodingException {
        char[] hexDigits = {
                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b',
                'c', 'd', 'e', 'f'
            };

        byte[] strTemp = s.getBytes("UTF-8");
        MessageDigest mdTemp = MessageDigest.getInstance("MD5");
        mdTemp.update(strTemp);

        byte[] md = mdTemp.digest();
        int j = md.length;
        char[] str = new char[j * 2];
        int k = 0;

        for (int i = 0; i < j; i++) {
            byte byte0 = md[i];
            str[k++] = hexDigits[byte0 >>> 4 & 0xf];
            str[k++] = hexDigits[byte0 & 0xf];
        }

        return new String(str);
    }
}