public String valueBeforeMD5 = "";
public String valueAfterMD5 = "";
private static Random myRand;
private static SecureRandom mySecureRand;
private static String s_id;
static {
mySecureRand = new SecureRandom();
long secureInitializer = mySecureRand.nextLong();
myRand = new Random(secureInitializer);
try {
s_id = InetAddress.getLocalHost().toString();
} 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();
// 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));
/*
* 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();
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< 100; i++) {
RandomGUID myGUID = new RandomGUID();
System.out.println("Seeding String=" + myGUID.valueBeforeMD5);
System.out.println("rawGUID=" + myGUID.valueAfterMD5);
System.out.println("RandomGUID=" + myGUID.toString());
}
}
}