Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
//License from project: Open Source License 

import java.math.BigInteger;

public class Main {
    final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();

    public static boolean isGoodPrime(byte[] prime, int g) {
        if (!(g >= 2 && g <= 7)) {
            return false;
        }

        if (prime.length != 256 || prime[0] >= 0) {
            return false;
        }

        BigInteger dhBI = new BigInteger(1, prime);

        if (g == 2) { // p mod 8 = 7 for g = 2;
            BigInteger res = dhBI.mod(BigInteger.valueOf(8));
            if (res.intValue() != 7) {
                return false;
            }
        } else if (g == 3) { // p mod 3 = 2 for g = 3;
            BigInteger res = dhBI.mod(BigInteger.valueOf(3));
            if (res.intValue() != 2) {
                return false;
            }
        } else if (g == 5) { // p mod 5 = 1 or 4 for g = 5;
            BigInteger res = dhBI.mod(BigInteger.valueOf(5));
            int val = res.intValue();
            if (val != 1 && val != 4) {
                return false;
            }
        } else if (g == 6) { // p mod 24 = 19 or 23 for g = 6;
            BigInteger res = dhBI.mod(BigInteger.valueOf(24));
            int val = res.intValue();
            if (val != 19 && val != 23) {
                return false;
            }
        } else if (g == 7) { // p mod 7 = 3, 5 or 6 for g = 7.
            BigInteger res = dhBI.mod(BigInteger.valueOf(7));
            int val = res.intValue();
            if (val != 3 && val != 5 && val != 6) {
                return false;
            }
        }

        String hex = bytesToHex(prime);
        if (hex.equals(
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{
            return true;
        }

        BigInteger dhBI2 = dhBI.subtract(BigInteger.valueOf(1)).divide(BigInteger.valueOf(2));
        return !(!dhBI.isProbablePrime(30) || !dhBI2.isProbablePrime(30));
    }

    public static String bytesToHex(byte[] bytes) {
        if (bytes == null) {
            return "";
        }
        char[] hexChars = new char[bytes.length * 2];
        int v;
        for (int j = 0; j < bytes.length; j++) {
            v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }
}