Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
import java.math.BigInteger;

public class Main {
    private static BigInteger ONE = BigInteger.valueOf(1);

    private static BigInteger findSquareRoot(BigInteger alpha, BigInteger p) {
        BigInteger beta = null;
        if (p.mod(BigInteger.valueOf(4)).compareTo(BigInteger.valueOf(3)) == 0) {
            BigInteger k = p.shiftRight(2).add(ONE);
            beta = alpha.modPow(k, p);
        } else if (p.mod(BigInteger.valueOf(8)).compareTo(BigInteger.valueOf(5)) == 0) {
            System.out.println("p = 8 mod 5");
            BigInteger k = p.subtract(BigInteger.valueOf(5)).divide(BigInteger.valueOf(8));
            BigInteger gamma = alpha.multiply(BigInteger.valueOf(2)).modPow(k, p);
            BigInteger i = alpha.multiply(BigInteger.valueOf(2)).multiply(gamma.pow(2)).mod(p);
            beta = alpha.multiply(gamma).multiply(i.subtract(ONE)).mod(p);
        } else if (p.mod(BigInteger.valueOf(8)).compareTo(BigInteger.valueOf(1)) == 0) {
            beta = null;
            //TODO
            System.out.println("finding square root not fully implemented yet");
        }
        return beta;
    }
}