RSA TOC2

RSA.java

import java.math.BigInteger;
import java.security.SecureRandom;

public class RSA {
	private static BigInteger n;
	private static BigInteger d;
	private static BigInteger e;
	
	public static BigInteger randomPrimeBigIntegerRange(int bitLengthFrom, int bitLengthtTo){
		SecureRandom rnd = new SecureRandom();
		BigInteger two = new BigInteger("2");
		BigInteger r;
		int i =0;
		do{
		    r = BigInteger.probablePrime(bitLengthtTo,rnd);
		}while(r.compareTo(two.pow(bitLengthFrom)) <= 0);
		return r;
	}
	
	public static BigInteger encrypt(BigInteger message) { 
		return message.modPow(e, n); 
	}
	
	public static BigInteger decrypt(BigInteger message) { 
		return message.modPow(d, n); 
	}
	
	public static void main(String[] args) {
		BigInteger p = randomPrimeBigIntegerRange(31,32);
		BigInteger q = randomPrimeBigIntegerRange(31,32);
		n = p.multiply(q); 
		BigInteger phy = (p.subtract(BigInteger.ONE)).multiply(q.subtract(BigInteger.ONE)); 
		e = new BigInteger("65537"); 
		while (phy.gcd(e).intValue() > 1) { 
			e =e.add(new BigInteger("2")); 
		} 
		d = e.modInverse(phy);
		BigInteger s1 = new BigInteger("55010923");
		BigInteger s2 = new BigInteger("55011222");
		BigInteger m = s1.multiply(s2);
		System.out.println("M is (55010923*55011222):"+m);
		BigInteger cipher = encrypt(m);
		BigInteger mPrime = decrypt(cipher);
		System.out.println("Cipher Message :"+cipher);
		System.out.println("Decrypt :"+mPrime);
		if(m.equals(mPrime)){
			System.out.println("Succeed");
		}else{
			System.out.println("Fail");
		}
	}
}