2018-2019-20175225 实验五《网络编程与安全》实验报告

实验步骤

任务一

• 两人一组结对编程
• 结对实现中缀表达式转后缀表达式的功能 MyBC.java
• 结对实现从上面功能中获取的表达式中实现后缀表达式求值的功能,调用MyDC.java

实验过程

• 将运算符写在两个操作数中间的表达式，称为“中缀表达式”，如1+2*(3-4)+5。在中缀表达式中，运算符具有不同的优先级，圆括号用于改变运算符的运算次序，所以求值过程不能直接按照从左到右的顺序进行。

• 将运算符写在两个操作数之后的表达式称为“后缀表达式”，如上面的中缀表达式可转换为后缀表达式1 2 3 4 - * + 5 +。后缀表达式中没有括号，而且运算符没有优先级。后缀表达式的求值过程能够严格地从左到右按顺序进行，符合运算器的求值规律。

• 表达式求值算法分两步进行：①中缀转后缀；②求后缀表达式的值。

• 由中缀式求得后缀式可以使用栈，伪代码如下：

  • 设立一个栈，存放运算符，首先栈为空；
  • 从左到右扫描中缀式，若遇到操作数，直接输出，并输出一个空格作为两个操作数的分隔符；
  • 若遇到运算符，则与栈顶比较，比栈顶级别高则进栈，否则退出栈顶元素并输出，然后输出一个空格作分隔符；
  • 若遇到左括号，进栈；若遇到右括号，则一直退栈输出，直到退到左括号止。
  • 当栈变成空时，输出的结果即为后缀表达式。

实验主要代码

• 中缀转后缀

package shiyan5;

import java.util.Stack;
public class MyBC{
    String jieguo = "";
    public MyBC (String[] args) {
        Stack<String> z = new Stack<String>();
        String t = "";
        for (int i = 0; i < args.length; i++) {
            switch (args[i]) {
                case "(":
                    z.push(args[i]);
                    break;
                case "+":
                case "-":
                    while(z.empty() != true) {
                        t = z.pop();
                        if (t.equals("(")) {
                            z.push(t);
                            break;
                        }
                        jieguo = jieguo + t + " ";
                    }
                    z.push(args[i]);
                    break;
                case "*":
                case "/":
                    while(z.empty() != true) {
                        t = z.pop();
                        if (t.equals("+") || t.equals("-") || t.equals("(")) {
                            z.push(t);
                            break;
                        }
                        jieguo = jieguo + t + " ";
                    }
                    z.push(args[i]);
                    break;
                case ")":
                    while (z.empty()== false) {
                        t = z.pop();
                        if (t.equals("(")) {
                            break;
                        } else {
                            jieguo = jieguo + t + " ";
                        }
                    }
                    break;
                case" ":
                    break;

                default:
                    jieguo = jieguo + args[i] + " ";
                    break;
            }

        }

        while (z.empty() == false) {
            jieguo = jieguo + z.pop() + " ";
        }
        System.out.println(jieguo);
    }
}

实验结果

任务二

• 结对编程：1人负责客户端，一人负责服务器
• 注意责任归宿，要会通过测试证明自己没有问题
• 基于Java Socket实现客户端/服务器功能，传输方式用TCP
• 客户端让用户输入中缀表达式，然后把中缀表达式调用MyBC.java的功能转化为后缀表达式，把后缀表达式通过网络发送给服务器
• 服务器接收到后缀表达式，调用MyDC.java的功能计算后缀表达式的值，把结果发送给客户端
• 客户端显示服务器发送过来的结果

实验过程

• 通过终端中输入ipconfig 或者使用InetAddress类的静态方法getLocalHost()获得一个InetAddress的对象获取服务器端IP地址
• 客户端通过命令行输入待连接的服务器的IP地址
  • 调用InetAddress类中的geetByName方法获取输入的IP地址；
  • 创建一个套接字，可以使用Socket的构造方法，如：public Socket(java.lang.String host, int port) 其中，host是远程机器名或IP地址，port是远程应用程序的端口号。
  • 方法getInputStream() 获得一个输入流
  • 方法getOutputStream() 获得一个输出流
• 服务器端调用ServerSocket实现套接字
  • 使用accept() 方法连接客户端和服务器的套接字
  • 方法getInputStream() 获得一个输入流
  • 方法getOutputStream() 获得一个输出流

实验代码

• 获取本机的地址

package shiyan5;

import java.net.*;
public class getHostAddress {
    public static void main(String[] args) {
        try{
            InetAddress hostaddress = InetAddress.getLocalHost();
            System.out.println(hostaddress.toString());
        }catch (UnknownHostException e){
            System.out.println(e);
        }
    }
}

• 客户端

package 实验五;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;
import java.util.Scanner;

public class Client {
    public static void main(String[] args) {
        Scanner inn = new Scanner(System.in);
        Socket mysocket;
        DataInputStream in = null;
        DataOutputStream out = null;
        try{
            mysocket = new Socket("192.168.56.1",2010);
            in = new DataInputStream(mysocket.getInputStream());
            out = new DataOutputStream(mysocket.getOutputStream());
            System.out.println("请输入中缀表达式：");
            String infix = inn.nextLine();
            String [] str = infix.split(" ");
            System.out.println("已传递后缀表达式");
            MyBC suffix =new MyBC(str);
            out.writeUTF(suffix.jieguo);
            String result = in.readUTF();
            System.out.println("已收到计算结果"+result);
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接"+e);
        }
    }
}

• 服务器端

package 实验五;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class Sever {
    public static void main(String[] args) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;

        try{
            serverForClient = new ServerSocket(2010);
        }catch (IOException e){
            System.out.println("双方已断开连接"+e);
        }
        try{
            System.out.println("准备接受对方传来的问题");
            socketOnServer = serverForClient.accept();
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());
            String suffix = in.readUTF();
            String [] str = suffix.split(" ");
            System.out.println("收到问题，正在解决:"+suffix);
            System.out.println("已传输得出结果：");
            MyDC myDC = new MyDC(str);
            String answer =  String.valueOf(myDC.answer);
            out.writeUTF(answer+"");
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接");
        }
    }
}

实验结果

• 客户端

• 服务器端

任务三

• 加密结对编程：1人负责客户端，一人负责服务器
• 注意责任归宿，要会通过测试证明自己没有问题
• 基于Java Socket实现客户端/服务器功能，传输方式用TCP
• 客户端让用户输入中缀表达式，然后把中缀表达式调用MyBC.java的功能转化为后缀表达式，把后缀表达式用DES或AES算法加密后通过网络把密文发送给服务器
• 服务器接收到后缀表达式表达式后，进行解密（和客户端协商密钥，可以用数组保存），然后调用MyDC.java的功能计算后缀表达式的值，把结果发送给客户端
• 客户端显示服务器发送过来的结果

实验过程

• 实现DES加密主要有以下几个步骤：
  • 对称密钥的生成和保存；
  • 使用对称密钥进行加密和解密；
  • 从文件中获取加密时使用的密钥，使用密钥进行解密；
• 生成密钥文件

实验代码

• 客户端

package 实验五;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;
import java.util.Scanner;

public class Client1{
    public static void main(String[] args) {
        Scanner inn = new Scanner(System.in);
        Socket mysocket;
        DataInputStream in = null;
        DataOutputStream out = null;
        try{
            mysocket = new Socket("192.168.56.1",2010);
            in = new DataInputStream(mysocket.getInputStream());
            out = new DataOutputStream(mysocket.getOutputStream());
            KeyGenerator kg = KeyGenerator.getInstance("DESede");
            kg.init(168);
            SecretKey k = kg.generateKey();
            byte []kb = k.getEncoded();
            out.writeUTF(kb.length+ "");
            System.out.println("产生的密钥为");
            for(int i=0;i<kb.length;i++) {
                System.out.print(kb[i]+ " ");
                out.writeUTF(kb[i] +"");
            }
            System.out.println("\n请输入中缀表达式：");
            String infix = inn.nextLine();
            String [] str = infix.split(" ");
            System.out.println("后缀表达式为");
            MyBC suffix =new MyBC(str);
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.ENCRYPT_MODE,k);
            byte ptext[] = suffix.jieguo.getBytes("UTF8");
            byte ctext[] = cp.doFinal(ptext);
            out.writeUTF(ctext.length + "");
            for(int i=0;i<ctext.length;i++) {
                out.writeUTF(ctext[i] +"");
            }
            String result = in.readUTF();
            System.out.println("已收到计算结果"+result);
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接"+e);
        }
    }
}

• 服务器端

package 实验五;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class Sever1{
    public static void main(String[] args) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try{
            serverForClient = new ServerSocket(2010);
        }catch (IOException e){
            System.out.println("双方已断开连接"+e);
        }
        try{
            System.out.println("准备接受对方传来的问题");
            socketOnServer = serverForClient.accept();
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());
            String keylength = in.readUTF();
            byte []kb = new byte[Integer.parseInt(keylength)];
            System.out.println("收到的密钥为：");
            for(int i = 0;i<Integer.parseInt(keylength);i++) {
                String str = in.readUTF();
                kb[i] = Byte.parseByte(str);
                System.out.print(kb[i] + " ");
            }
            SecretKeySpec k = new SecretKeySpec(kb, "DESede");
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            String clength = in.readUTF();
            byte ctext[] = new byte[Integer.parseInt(clength)];
            for (int i = 0;i<Integer.parseInt(clength);i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            byte[] ptext = cp.doFinal(ctext);
            String suffix = new String(ptext,"UTF8");
            String [] str = suffix.split(" ");
            System.out.println("\n收到问题，解密后的后缀表达式为:"+suffix);
            System.out.println("已传输得出结果：");
            MyDC myDC = new MyDC(str);
            String answer =  String.valueOf(myDC.answer);
            out.writeUTF(answer+"");
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接");
        }
    }
}

实验结果

• 客户端
  

• 服务器端
  

任务四

• 密钥分发结对编程：1人负责客户端，一人负责服务器
• 注意责任归宿，要会通过测试证明自己没有问题
• 基于Java Socket实现客户端/服务器功能，传输方式用TCP
• 客户端让用户输入中缀表达式，然后把中缀表达式调用MyBC.java的功能转化为后缀表达式，把后缀表达式用DES或AES算法加密通过网络把密文发送给服务器
• 客户端和服务器用DH算法进行DES或AES算法的密钥交换
• 服务器接收到后缀表达式表达式后，进行解密，然后调用MyDC.java的功能计算后缀表达式的值，把结果发送给客户端
• 客户端显示服务器发送过来的结果

实验过程

• 两人先使用Key_DH类生成各自的DH公钥和私钥
• 俩人使用对方的公钥和自己的私钥，用KeyAgree，生成共享密钥
• 客户端使用共享密钥对原有的密钥进行加密，并把密文和加密后的密钥传输给服务器
• 服务器先用共享密钥对客户端加密的密钥进行解密，再用解密后的密钥解密密文

实验代码

• 客户端

package 实验五;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.security.*;
import java.util.Scanner;
import java.net.*;
public class Client2 {
    public static void main(String[] args) {
        Scanner inn = new Scanner(System.in

        );
        Socket mysocket;
        DataInputStream in = null;
        DataOutputStream out = null;
        try{
            mysocket = new Socket("192.168.56.1",2010);
                    in = new DataInputStream(mysocket.getInputStream());
            out = new DataOutputStream(mysocket.getOutputStream());
            Key_DH.DH ("Lpub.dat","Lpri.dat");
            FileInputStream my = new FileInputStream("Lpub.dat");
            ObjectInputStream mypub = new ObjectInputStream(my);
            Key kp = (Key) mypub.readObject();
            ByteArrayOutputStream DH = new ByteArrayOutputStream();
            ObjectOutputStream myDH = new ObjectOutputStream(DH);
            myDH.writeObject(kp);
            byte []pub = DH.toByteArray();
            out.writeUTF(pub.length+"");
            for(int i=0;i<pub.length;i++) {
                out.writeUTF(pub[i]+ "");
            }
            Thread.sleep(1000);
            int length = Integer.parseInt(in.readUTF());
            byte cpub[] = new byte[length];
            for(int i=0;i<length;i++) {
                String temp = in.readUTF();
                cpub[i] = Byte.parseByte(temp);
            }
            ByteArrayInputStream ckey1 = new ByteArrayInputStream(cpub);
            ObjectInputStream ckey = new ObjectInputStream(ckey1);
            Key k = (Key) ckey.readObject();
            FileOutputStream f2 = new FileOutputStream("W1pub.dat");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k);
            KeyAgree.Agree("W1pub.dat","Lpri.dat");
            FileInputStream f = new FileInputStream("sb.dat");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密钥为：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+" ");
            }
            System.out.println("\n请输入中缀表达式：");
            String infix = inn.nextLine();
            String [] str = infix.split(" ");
            System.out.println("已传递后缀表达式");
            MyBC suffix =new MyBC(str);
            SecretKeySpec k1 = new SecretKeySpec(keysb, "DESede");
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.ENCRYPT_MODE, k1);
            byte ptext[] = suffix.jieguo.getBytes("UTF8");
            byte ctext[] = cp.doFinal(ptext);
            System.out.println("加密后的后缀表达式为：");
            for (int i = 0; i < ctext.length; i++) {
                System.out.print(ctext[i] + " ");
            }
            out.writeUTF(ctext.length + "");
            for (int i = 0; i < ctext.length; i++) {
                out.writeUTF(ctext[i] + "");
            }
            String result = in.readUTF();
            System.out.println("\n已收到计算结果"+result);
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接"+e);
        }
    }
}

• 服务器端

package 实验五;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.Key;
public class Sever2{
    public static void main(String[] args) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try{
            serverForClient = new ServerSocket(2010);
        }catch (IOException e){
            System.out.println("双方已断开连接"+e);
        }
        try{
            System.out.println("准备接受对方传来的问题");
            socketOnServer = serverForClient.accept();
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());
            Key_DH.DH("Wpub.dat","Wpri.dat");
            int length = Integer.parseInt(in.readUTF());
            byte cpub[] = new byte[length];
            for(int i=0;i<length;i++) {
                String temp = in.readUTF();
                cpub[i] = Byte.parseByte(temp);
            }
            ByteArrayInputStream ckey1 = new ByteArrayInputStream(cpub);
            ObjectInputStream ckey = new ObjectInputStream(ckey1);
            Key k1 = (Key) ckey.readObject();
            FileOutputStream f2 = new FileOutputStream("Lpub.dat");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k1);
            FileInputStream my = new FileInputStream("Wpub.dat");
            ObjectInputStream mypub = new ObjectInputStream(my);
            Key kp = (Key) mypub.readObject();
            ByteArrayOutputStream DH = new ByteArrayOutputStream();
            ObjectOutputStream myDH = new ObjectOutputStream(DH);
            myDH.writeObject(kp);
            byte []pub = DH.toByteArray();
            out.writeUTF(pub.length+"");
            for(int i=0;i<pub.length;i++) {
                out.writeUTF(pub[i]+ "");
            }
            KeyAgree.Agree("Lpub.dat","Wpri.dat");
            FileInputStream f = new FileInputStream("sb.dat");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密钥为：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+" ");
            }
            SecretKeySpec k = new SecretKeySpec(keysb, "DESede");
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            String clength = in.readUTF();
            byte ctext[] = new byte[Integer.parseInt(clength)];
            for (int i = 0; i < Integer.parseInt(clength); i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            byte[] ptext = cp.doFinal(ctext);
            String suffix = new String(ptext, "UTF8");
            String [] str = suffix.split(" ");
            System.out.println("\n收到问题，正在解密后缀表达式:"+suffix);
            System.out.println("已传输得出结果：");
            MyDC myDC = new MyDC(str);
            String answer =  String.valueOf(myDC.answer);
            out.writeUTF(answer+"");
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接");
        }
    }
}

• KeyAgree

package 实验五;

import javax.crypto.KeyAgreement;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.security.PrivateKey;
import java.security.PublicKey;

public class KeyAgree {
    public static void Agree(String str1,String str2) throws Exception{
        // 读取对方的DH公钥
        FileInputStream f1=new FileInputStream(str1);
        ObjectInputStream b1=new ObjectInputStream(f1);
        PublicKey  pbk=(PublicKey)b1.readObject( );
//读取自己的DH私钥
        FileInputStream f2=new FileInputStream(str2);
        ObjectInputStream b2=new ObjectInputStream(f2);
        PrivateKey  prk=(PrivateKey)b2.readObject( );
        // 执行密钥协定
        KeyAgreement ka=KeyAgreement.getInstance("DH");
        ka.init(prk);
        ka.doPhase(pbk,true);
        //生成共享信息
        byte[ ] sb=ka.generateSecret();
        FileOutputStream fsb = new FileOutputStream("sb.dat");
        fsb.write(sb);
    }
}

• Key_DH

package 实验五;

import javax.crypto.spec.DHParameterSpec;
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;

public class Key_DH{
    private static final byte skip1024ModulusBytes[] = {
            (byte)0xF4, (byte)0x88, (byte)0xFD, (byte)0x58,
            (byte)0x4E, (byte)0x49, (byte)0xDB, (byte)0xCD,
            (byte)0x20, (byte)0xB4, (byte)0x9D, (byte)0xE4,
            (byte)0x91, (byte)0x07, (byte)0x36, (byte)0x6B,
            (byte)0x33, (byte)0x6C, (byte)0x38, (byte)0x0D,
            (byte)0x45, (byte)0x1D, (byte)0x0F, (byte)0x7C,
            (byte)0x88, (byte)0xB3, (byte)0x1C, (byte)0x7C,
            (byte)0x5B, (byte)0x2D, (byte)0x8E, (byte)0xF6,
            (byte)0xF3, (byte)0xC9, (byte)0x23, (byte)0xC0,
            (byte)0x43, (byte)0xF0, (byte)0xA5, (byte)0x5B,
            (byte)0x18, (byte)0x8D, (byte)0x8E, (byte)0xBB,
            (byte)0x55, (byte)0x8C, (byte)0xB8, (byte)0x5D,
            (byte)0x38, (byte)0xD3, (byte)0x34, (byte)0xFD,
            (byte)0x7C, (byte)0x17, (byte)0x57, (byte)0x43,
            (byte)0xA3, (byte)0x1D, (byte)0x18, (byte)0x6C,
            (byte)0xDE, (byte)0x33, (byte)0x21, (byte)0x2C,
            (byte)0xB5, (byte)0x2A, (byte)0xFF, (byte)0x3C,
            (byte)0xE1, (byte)0xB1, (byte)0x29, (byte)0x40,
            (byte)0x18, (byte)0x11, (byte)0x8D, (byte)0x7C,
            (byte)0x84, (byte)0xA7, (byte)0x0A, (byte)0x72,
            (byte)0xD6, (byte)0x86, (byte)0xC4, (byte)0x03,
            (byte)0x19, (byte)0xC8, (byte)0x07, (byte)0x29,
            (byte)0x7A, (byte)0xCA, (byte)0x95, (byte)0x0C,
            (byte)0xD9, (byte)0x96, (byte)0x9F, (byte)0xAB,
            (byte)0xD0, (byte)0x0A, (byte)0x50, (byte)0x9B,
            (byte)0x02, (byte)0x46, (byte)0xD3, (byte)0x08,
            (byte)0x3D, (byte)0x66, (byte)0xA4, (byte)0x5D,
            (byte)0x41, (byte)0x9F, (byte)0x9C, (byte)0x7C,
            (byte)0xBD, (byte)0x89, (byte)0x4B, (byte)0x22,
            (byte)0x19, (byte)0x26, (byte)0xBA, (byte)0xAB,
            (byte)0xA2, (byte)0x5E, (byte)0xC3, (byte)0x55,
            (byte)0xE9, (byte)0x2F, (byte)0x78, (byte)0xC7
    };
    // The SKIP 1024 bit modulus
    private static final BigInteger skip1024Modulus
            = new BigInteger(1, skip1024ModulusBytes);
    // The base used with the SKIP 1024 bit modulus
    private static final BigInteger skip1024Base = BigInteger.valueOf(2);
    public static void DH(String str1,String str2) throws Exception{
        DHParameterSpec DHP=
                new DHParameterSpec(skip1024Modulus,skip1024Base);

        KeyPairGenerator kpg= KeyPairGenerator.getInstance("DH");
        kpg.initialize(DHP);
        KeyPair kp=kpg.genKeyPair();

        PublicKey pbk=kp.getPublic();
        PrivateKey prk=kp.getPrivate();
        // 保存公钥
        FileOutputStream  f1=new FileOutputStream(str1);
        ObjectOutputStream b1=new  ObjectOutputStream(f1);
        b1.writeObject(pbk);
        // 保存私钥
        FileOutputStream  f2=new FileOutputStream(str2);
        ObjectOutputStream b2=new  ObjectOutputStream(f2);
        b2.writeObject(prk);
    }
}

实验结果

• 客户端
  

• 服务器端
  

任务五

• 完整性校验结对编程：1人负责客户端，一人负责服务器
• 注意责任归宿，要会通过测试证明自己没有问题
• 基于Java Socket实现客户端/服务器功能，传输方式用TCP
• 客户端让用户输入中缀表达式，然后把中缀表达式调用MyBC.java的功能转化为后缀表达式，把后缀表达式用3DES或AES算法加密通过网络把密文和明文的MD5値发送给服务器
• 客户端和服务器用DH算法进行3DES或AES算法的密钥交换
• 服务器接收到后缀表达式表达式后，进行解密，解密后计算明文的MD5值，和客户端传来的MD5进行比较，一致则调用MyDC.java的功能计算后缀表达式的值，把结果发送给客户端
• 客户端显示服务器发送过来的结果

实验代码

• 客户端

package 实验五;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.net.Socket;
import java.security.Key;
import java.util.Scanner;

public class Client3 {
    public static void main(String[] args) {
        Scanner inn = new Scanner(System.in

        );
        Socket mysocket;
        DataInputStream in = null;
        DataOutputStream out = null;
        try{
            mysocket = new Socket("192.168.56.1",2010);
                    in = new DataInputStream(mysocket.getInputStream());
            out = new DataOutputStream(mysocket.getOutputStream());
            Key_DH.DH("Lpub.dat","Lpri.dat");
            FileInputStream my = new FileInputStream("Lpub.dat");
            ObjectInputStream mypub = new ObjectInputStream(my);
            Key kp = (Key) mypub.readObject();
            ByteArrayOutputStream DH = new ByteArrayOutputStream();
            ObjectOutputStream myDH = new ObjectOutputStream(DH);
            myDH.writeObject(kp);
            byte []pub = DH.toByteArray();
            out.writeUTF(pub.length+"");
            for(int i=0;i<pub.length;i++) {
                out.writeUTF(pub[i]+ "");
            }
            Thread.sleep(1000);
            int length = Integer.parseInt(in.readUTF());
            byte cpub[] = new byte[length];
            for(int i=0;i<length;i++) {
                String temp = in.readUTF();
                cpub[i] = Byte.parseByte(temp);
            }
            ByteArrayInputStream ckey1 = new ByteArrayInputStream(cpub);
            ObjectInputStream ckey = new ObjectInputStream(ckey1);
            Key k = (Key) ckey.readObject();
            FileOutputStream f2 = new FileOutputStream("W1pub.dat");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k);
            KeyAgree.Agree("W1pub.dat","Lpri.dat");
            FileInputStream f = new FileInputStream("sb.dat");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密钥为：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+" ");
            }
            System.out.println("\n请输入中缀表达式：");
            String infix = inn.nextLine();
            String [] str = infix.split(" ");
            System.out.println("已传递后缀表达式");
            MyBC suffix =new MyBC(str);
            String mtoMD5 = DigestPass.MD5(suffix.jieguo);
            System.out.println("明文的MD5值为："+mtoMD5);
            out.writeUTF(mtoMD5);
            SecretKeySpec k1 = new SecretKeySpec(keysb, "DESede");
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.ENCRYPT_MODE, k1);
            byte ptext[] = suffix.jieguo.getBytes("UTF8");
            byte ctext[] = cp.doFinal(ptext);
            System.out.println("加密后的后缀表达式为：");
            for (int i = 0; i < ctext.length; i++) {
                System.out.print(ctext[i] + " ");
            }
            out.writeUTF(ctext.length + "");
            for (int i = 0; i < ctext.length; i++) {
                out.writeUTF(ctext[i] + "");
            }
            String result = in.readUTF();
            System.out.println("\n已收到计算结果"+result);
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接"+e);
        }
    }
}

• 服务器端

package 实验五;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.Key;
public class Sever3 {
    public static void main(String[] args) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;

        try{
            serverForClient = new ServerSocket(2010);
        }catch (IOException e){
            System.out.println("双方已断开连接"+e);
        }
        try{
            System.out.println("准备接受对方传来的问题");
            socketOnServer = serverForClient.accept();
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());
            Key_DH.DH("Wpub.dat","Wpri.dat");
            int length = Integer.parseInt(in.readUTF());
            byte cpub[] = new byte[length];
            for(int i=0;i<length;i++) {
                String temp = in.readUTF();
                cpub[i] = Byte.parseByte(temp);
            }
            ByteArrayInputStream ckey1 = new ByteArrayInputStream(cpub);
            ObjectInputStream ckey = new ObjectInputStream(ckey1);
            Key k1 = (Key) ckey.readObject();
            FileOutputStream f2 = new FileOutputStream("L1pub.dat");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k1);
            FileInputStream my = new FileInputStream("Wpub.dat");
            ObjectInputStream mypub = new ObjectInputStream(my);
            Key kp = (Key) mypub.readObject();
            ByteArrayOutputStream DH = new ByteArrayOutputStream();
            ObjectOutputStream myDH = new ObjectOutputStream(DH);
            myDH.writeObject(kp);
            byte []pub = DH.toByteArray();
            out.writeUTF(pub.length+"");
            for(int i=0;i<pub.length;i++) {
                out.writeUTF(pub[i]+ "");
            }
            KeyAgree.Agree("L1pub.dat","Wpri.dat");
            FileInputStream f = new FileInputStream("sb.dat");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密钥为：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+" ");
            }
            String c = in.readUTF();
            SecretKeySpec k = new SecretKeySpec(keysb, "DESede");
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            String clength = in.readUTF();
            byte ctext[] = new byte[Integer.parseInt(clength)];
            for (int i = 0; i < Integer.parseInt(clength); i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            byte[] ptext = cp.doFinal(ctext);
            String suffix = new String(ptext, "UTF8");
            String [] str = suffix.split(" ");
            System.out.println("\n收到问题，解密后缀表达式为:"+suffix);
            String mtoMD5 = DigestPass.MD5(suffix);
            System.out.println("MD5的值为"+ mtoMD5);
            if(mtoMD5.equals(c)) {
                System.out.println("传递的MD5值和解密的后缀表达式的MD5值相同，可以解密！");
                System.out.println("已传输得出结果：");
                MyDC myDC = new MyDC(str);
                String answer = String.valueOf(myDC.answer);
                out.writeUTF(answer + "");
            }
            else {
                System.out.println("密文有误，不能解密！");
            }
            Thread.sleep(500);
        }catch (Exception e){
            System.out.println("双方已断开连接");
        }
    }
}

实验结果

• 客户端
  

• 服务器端
  

码云链接