% package org.owasp.java.crypto; import java.security.SecureRandom; import java.security.NoSuchAlgorithmException; import sun.misc.BASE64Encoder; /** * @author Joe Prasanna Kumar * This program provides the functionality for Generating a Secure Random Number. * * There are 2 ways to generate a Random number through SecureRandom. * 1. By calling nextBytes method to generate Random Bytes * 2. Using setSeed(byte[]) to reseed a Random object * */ public class SecureRandomGen { /** * @param args */ public static void main(String[] args) { try { // Initialize a secure random number generator SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG"); // Method 1 - Calling nextBytes method to generate Random Bytes byte[] bytes = new byte[512]; secureRandom.nextBytes(bytes); // Printing the SecureRandom number by calling secureRandom.nextDouble() System.out.println(" Secure Random # generated by calling nextBytes() is " + secureRandom.nextDouble()); // Method 2 - Using setSeed(byte[]) to reseed a Random object int seedByteCount = 10; byte[] seed = secureRandom.generateSeed(seedByteCount); // TBR System.out.println(" Seed value is " + new BASE64Encoder().encode(seed)); secureRandom.setSeed(seed); System.out.println(" Secure Random # generated using setSeed(byte[]) is " + secureRandom.nextDouble()); } catch (NoSuchAlgorithmException noSuchAlgo) { System.out.println(" No Such Algorithm exists " + noSuchAlgo); } } } %