Java实现ElGamal算法签名

今晚有点迟了，具体说明明天再来补
Elgamal.java

package elgamal;

import java.math.BigInteger;
import java.lang.Math;
import java.util.Random;
import java.io.*;

public class ElGamal {

    private static final BigInteger ONE = BigInteger.ONE;

    // 获取随机大素数
    public static BigInteger getPrime(int bitLenth) {
        BigInteger p = BigInteger.probablePrime(bitLenth, new Random());
        while(!p.isProbablePrime(6)) {
            p.nextProbablePrime();
        }
        return p;
    }

    // 枚举遍历求生成元g
    public static BigInteger getG(BigInteger p, BigInteger p_MinusOne) {
        BigInteger g = null;

        outterLoop: for (int i = 2; i < 50; i++) {
            for (int x1 = 1; x1 <= Integer.valueOf(p_MinusOne.toString()); x1++) {
                String str1 = String.valueOf(i);
                String str2 = String.valueOf(x1);
                BigInteger tmp1 = new BigInteger(str1);
                BigInteger tmp2 = new BigInteger(str2);
                if (tmp1.modPow(tmp2, p).compareTo(ONE) == 0 && tmp2.compareTo(p_MinusOne) == -1) {
                    break;
                } else if (tmp1.modPow(tmp2, p).compareTo(ONE) == 0 && tmp2.compareTo(p_MinusOne) == 0) {
                    g = tmp1;
                    break outterLoop;
                }
            }
        }

        return g;
    }

}

ReadFile.java

package elgamal;

import java.io.BufferedReader;  
import java.io.File;  
import java.io.FileReader;
import java.io.IOException;  

public class ReadFile {  
    public static String txt2String(File file) throws IOException{  

        StringBuilder result = new StringBuilder(); 
        // 建立数据的输入通道  
        FileReader fileReader = new FileReader(file);  
        //建立缓冲字符数组读取文件数据  
        char[] buf = new char[1024];  
        int length = 0 ;

        while((length = fileReader.read(buf))!=-1){  
            result.append(new String(buf,0,length));  
        }  

        return result.toString();

        /*StringBuilder result = new StringBuilder();  
        try{  
            BufferedReader br = new BufferedReader(new FileReader(file));//构造一个BufferedReader类来读取文件  
            String s = null;  
            while((s = br.readLine())!=null){//使用readLine方法，一次读一行  
                result.append(System.lineSeparator()+s);  
            }  
            br.close();      
        }catch(Exception e){  
            e.printStackTrace();  
        }  
        return result.toString();  */
    }  

    public static void main(String[] args) throws IOException{  
        File file = new File("H:/test.txt");  
        System.out.println(txt2String(file));  
    }  

}  

Main.java

package elgamal;

import java.io.File;
import java.io.IOException;
import java.math.BigInteger;
import java.util.Random;

public class Main {

    private static final BigInteger ONE = BigInteger.ONE;

    public static void main(String[] args) throws IOException {
        File file = new File("H:/test.txt");

        String m = ReadFile.txt2String(file);
        System.out.println("消息m = " + m);

        int length = m.length();

        // 随机的大素数p
        BigInteger p = ElGamal.getPrime(length);
        System.out.println("p = " + p.toString());

        // 下面计算时用到的p-1
        BigInteger p_MinusOne = p.subtract(ONE);
        System.out.println("p-1 = " + p_MinusOne.toString());

        // 枚举遍历求生成元g
        BigInteger g = null;
        g = ElGamal.getG(p, p_MinusOne);
        System.out.println("g = " + g.toString());

        // 随机数x,满足区间[2,p-1)
        BigInteger x = new BigInteger(length,new Random());
        System.out.println("x = " + x.toString());

        // y ≡ g^x（ mod p ）
        BigInteger y = g.modPow(x,p);
        System.out.println("y = " + y.toString());

        // 随机的大素数k,满足区间[2,p-1)
        BigInteger k = ElGamal.getPrime(length);
        System.out.println("k = " + k.toString());

        // k的逆元
        BigInteger k_Reverse = k.modInverse(p_MinusOne);
        System.out.println("k对p-1的逆元 = " + k_Reverse.toString());

        // a ≡ g^k ( mod p )
        BigInteger a = g.modPow(k,p);
        System.out.println("a = " + a.toString());

        // h(m)
        int hm = Math.abs(m.hashCode());
        String temp = String.valueOf(hm);
        String hmm = temp.substring(1, 5);
        BigInteger h_m = new BigInteger(hmm);
        System.out.println("h(m) = " + h_m.toString());

        BigInteger tmp1 = h_m.subtract(x.multiply(a));
        System.out.println("tmp1 = " + tmp1.toString());

        BigInteger tmp2 = tmp1.multiply(k_Reverse);
        System.out.println("tmp2 = " + tmp2.toString());

        BigInteger b = tmp2.mod(p_MinusOne);
        System.out.println("b = " + b.toString());

        System.out.println("消息m的数字签名为: " + a.toString() + "," + b.toString());

        BigInteger left = y.pow(a.intValue()).multiply(a.pow(b.intValue())).mod(p);
        System.out.println("left = " + left.toString());

        int unsignedH_m = h_m.intValue();
        if(unsignedH_m < 0) {
            unsignedH_m = -unsignedH_m;
        }
        BigInteger right = g.pow(unsignedH_m).mod(p);

        System.out.println("right = " + right.toString());

    }

}