BigInteger power and modPow

In this chapter you will learn:

How to calculate Power of BigInteger
How to BigInteger Mod Power

BigInteger's Power

BigInteger pow(int exponent) returns a BigInteger whose value is (this^exponent).

import java.math.BigInteger;
//  ja v a 2s  .co m
public class Main {
  public static void main(String[] argv) throws Exception {
    BigInteger bi1 = new BigInteger("1234567890123456890");
    int exponent = 2;

    bi1 = bi1.pow(exponent);
    System.out.println(bi1);
  }
}

The output:

BigInteger Mod Power

BigInteger modPow(BigInteger exponent, BigInteger m) returns a BigInteger whose value is (this^exponent mod m).

import java.math.BigInteger;
import java.security.SecureRandom;
/*  j a  va2 s. c  om*/
public class Main {
  public static void main(String[] args) throws Exception {
    int bitLength = 512; // 512 bits
    SecureRandom rnd = new SecureRandom();
    int certainty = 90; // 1 - 1/2(90) certainty
    System.out.println("BitLength : " + bitLength);
    BigInteger mod = new BigInteger(bitLength, certainty, rnd);
    BigInteger exponent = BigInteger.probablePrime(bitLength, rnd);
    BigInteger n = BigInteger.probablePrime(bitLength, rnd);

    BigInteger result = n.modPow(exponent, mod);
    System.out.println("Number ^ Exponent MOD Modulus = Result");
    System.out.println("Number");
    System.out.println(n);
    System.out.println("Exponent");
    System.out.println(exponent);
    System.out.println("Modulus");
    System.out.println(mod);
    System.out.println("Result");
    System.out.println(result);
  }
}