Java笔记-DH密钥交换

Posted 2021-09-07 IT1995

DH密钥交换主要是两个公式的编写，即：

    ·公钥计算公式；

    ·密钥计算公式；

生成随机数作为私钥

截图如下：

 

源码如下：

DH.java

package cn.it1995.tool;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Random;

public class DH {

    private static final int dhP = 45;
    private static final  int dhG = 9;

    private int mPriKey;

    //构造函数随机私钥
    public DH(){

        Random r = new Random();
        mPriKey = r.nextInt(20);
        System.out.println("dh priKey is : " + mPriKey);
    }

    //公钥计算公式计算出公钥
    public int getPublicKey(){

        return (int) (Math.pow(dhG, mPriKey) % dhP);
    }

    //使用对方公钥与自己私钥生成密钥
    //在把结果转256字节，AES密钥需要128字节或256字节
    public byte[] getSecretKey(long publicKey){

        int buf = (int) (Math.pow(publicKey, mPriKey) % dhP);
        return sha256(buf);
    }

    //转换成byte[256]类型，作为AES密钥
    private byte[] sha256(int data){

        try {

            MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
            messageDigest.update(DataSecret.int2Byte(data));
            return messageDigest.digest();
        }
        catch (NoSuchAlgorithmException e) {
            
            e.printStackTrace();
        }

        return new byte[]{-1};
    }
}

DataSecret.java

package cn.it1995.tool;

import org.apache.commons.codec.binary.Base64;

import java.io.UnsupportedEncodingException;
import java.nio.ByteBuffer;

public class DataSecret {


    public static byte[] encode(byte[] txt) throws UnsupportedEncodingException {

        return Base64.encodeBase64(txt);
    }

    public static byte[] decode(String txt){

        return Base64.decodeBase64(txt);
    }

    public static byte[] int2Byte(int data){

        ByteBuffer byteBuffer = ByteBuffer.allocate(4);
        byteBuffer.putInt(data);
        return byteBuffer.array();
    }
}

Main.java

 public static void main(String[] args) throws UnsupportedEncodingException {


     //查密钥
     DH dhC = new DH();
     DH dhS = new DH();

     int publicKeyC = dhC.getPublicKey();
     int publicKeyS = dhS.getPublicKey();

     byte[] secretC = dhC.getSecretKey(publicKeyS);
     byte[] secretS = dhS.getSecretKey(publicKeyC);

     System.out.println("client's secrete is : ");
     for(byte i : secretC){

         System.out.print(i + " ");
     }
     System.out.println("\\nserver's secrete is : ");
     for(byte i : secretS){

         System.out.print(i + " ");
     }
 }