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

public class Q2Tools {

    Q2Tools()
    {
        //Nothing to do here
    }
    
    public void generateRSA()
    {
        //Public Key:
        BigInteger e = new BigInteger("65537");

        //Generate p
        SecureRandom randomNum = new SecureRandom();
        BigInteger p = BigInteger.probablePrime(1024, randomNum);
        
        //Generate q
        BigInteger q = BigInteger.probablePrime(1024, randomNum);

        //Generate n
        BigInteger n = p.multiply(q);

        //Generate phi n
        BigInteger m = ((p.subtract(BigInteger.valueOf(1))).multiply((p.subtract(BigInteger.valueOf(1)))));



        System.out.println("E: "+e);
        System.out.println("P: "+p);
        System.out.println("Q: "+q);
        System.out.println("N: "+n);
        System.out.println("M: "+m);

    }

/**
 * Performs a fast modular exponation, (base^exponent)%modulus.
 * Takes input values as strings containg the numbers
 * @param base
 * @param exponent
 * @param modulus
 * @return
 */
    public BigInteger fme(String base, String exponent, String modulus)
    {
        BigInteger baseVal = new BigInteger(base);
        BigInteger exponentVal = new BigInteger(exponent);
        BigInteger modulusVal = new BigInteger(modulus);  
        
        if(modulusVal.equals(BigInteger.valueOf(1)))
        {  
            return BigInteger.valueOf(0);
        }

        BigInteger result = new BigInteger("1");

        while(exponentVal.compareTo(BigInteger.valueOf(0))==1)
        {   
            if(exponentVal.and(BigInteger.valueOf(1)).compareTo(BigInteger.valueOf(1))==0)
            {
               result = result.multiply(baseVal);
               result = result.mod(modulusVal);

            }

            exponentVal = exponentVal.shiftRight(1);
            baseVal = (baseVal.multiply(baseVal)).mod(modulusVal);
        }
        return result;
    }
}