1 package org.bouncycastle.crypto.generators; 2 3 import org.bouncycastle.crypto.params.DHParameters; 4 5 import java.math.BigInteger; 6 import java.security.SecureRandom; 7 8 public class DHParametersGenerator 9 { 10 private int size; 11 private int certainty; 12 private SecureRandom random; 13 14 private static final BigInteger TWO = BigInteger.valueOf(2); 15 16 /** 17 * Initialise the parameters generator. 18 * 19 * @param size bit length for the prime p 20 * @param certainty level of certainty for the prime number tests 21 * @param random a source of randomness 22 */ 23 public void init( 24 int size, 25 int certainty, 26 SecureRandom random) 27 { 28 this.size = size; 29 this.certainty = certainty; 30 this.random = random; 31 } 32 33 /** 34 * which generates the p and g values from the given parameters, 35 * returning the DHParameters object. 36 * <p> 37 * Note: can take a while... 38 */ 39 public DHParameters generateParameters() 40 { 41 // 42 // find a safe prime p where p = 2*q + 1, where p and q are prime. 43 // 44 BigInteger[] safePrimes = DHParametersHelper.generateSafePrimes(size, certainty, random); 45 46 BigInteger p = safePrimes[0]; 47 BigInteger q = safePrimes[1]; 48 BigInteger g = DHParametersHelper.selectGenerator(p, q, random); 49 50 return new DHParameters(p, g, q, TWO, null); 51 } 52 } 53
