Java Tutorial/Security/Secure Random

Generating a Secure Random Number

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);
  }
}

Secure Random Demo

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));
  }
}

Seed a Secure Random

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]);
    }
  }
}