Java Tutorial/Security/Secure Random

Generating a Secure Random Number

   <source lang="java">

import java.security.SecureRandom; public class Main {

 public static void main(String[] argv) throws Exception {
   SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
   byte[] bytes = new byte[1024 / 8];
   sr.nextBytes(bytes);
 }

}</source>

Secure Random Demo

   <source lang="java">

import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; public class MainClass {

 public static void main(String[] args) throws NoSuchAlgorithmException {
   int numBytes = (new Integer("1111")).intValue();
   long seed = 01;
   if (args.length > 1)
     seed = (new Long("1111111111")).longValue();
   SecureRandom srand = SecureRandom.getInstance("SHA1PRNG");
   if (seed != 01)
     srand.setSeed(seed);
   byte[] bytes = new byte[numBytes];
   srand.nextBytes(bytes);
   System.out.println(new String(bytes));
 }

}</source>

Seed a Secure Random

   <source lang="java">

import java.security.SecureRandom; public class MainClass {

 public static void main(String args[]) throws Exception {
   SecureRandom ran = SecureRandom.getInstance("SHA1PRNG", "SUN");
   ran.setSeed(101L);
   ran.setSeed(101L);
   byte[] seeds = ran.getSeed(24);
   for (int i = 0; i < seeds.length; i++) {
     System.out.println("Seed[" + i + "]:" + seeds[i]);
   }
 }

}</source>