Java第五次实验

Java第五次实验--网络编程与安全

任务一：

一、实验要求：

两人一组结对编程：
0. 参考http://www.cnblogs.com/rocedu/p/6766748.html#SECDSA

  1. 结对实现中缀表达式转后缀表达式的功能 MyBC.java
  2. 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
  3. 上传测试代码运行结果截图和码云链接

二、实验步骤：

1.参考娄老师提供的博客[http://www.cnblogs.com/rocedu/p/6766748.html#SECDSA]中的MyDC.java，将31-40行的代码填充可得如下代码：

import java.util.StringTokenizer;
import java.util.Stack;

public class MyDC {
    /**
     * constant for addition symbol
     */
    private final char ADD = '+';
    /**
     * constant for subtraction symbol
     */
    private final char SUBTRACT = '-';
    /**
     * constant for multiplication symbol
     */
    private final char MULTIPLY = '*';
    /**
     * constant for division symbol
     */
    private final char DIVIDE = '/';
    /**
     * the stack
     */
    private Stack<Integer> stack;

    public MyDC() {
        stack = new Stack<Integer>();
    }

    public int evaluate(String expr) {
        int op1, op2, result = 0;
        String token;
        StringTokenizer tokenizer = new StringTokenizer(expr);
        while (tokenizer.hasMoreTokens()) {
            token = tokenizer.nextToken();

            //如果是运算符，调用isOperator
            if (isOperator(token)) {
                //从栈中弹出操作数2
                op2 = stack.pop();
                //从栈中弹出操作数1
                op1 = stack.pop();
                //根据运算符和两个操作数调用evalSingleOp计算result;
                result=evalSingleOp(token.charAt(0), op1, op2);
                //计算result入栈;
                stack.push(result);
            } else//如果是操作数
                //操作数入栈;
                stack.push(Integer.parseInt(token));
        }

        return result;
    }

    private boolean isOperator(String token) {
        return (token.equals("+") || token.equals("-") ||
                token.equals("*") || token.equals("/"));
    }

    private int evalSingleOp(char operation, int op1, int op2) {
        int result = 0;

        switch (operation) {
            case ADD:
                result = op1 + op2;
                break;
            case SUBTRACT:
                result = op1 - op2;
                break;
            case MULTIPLY:
                result = op1 * op2;
                break;
            case DIVIDE:
                result = op1 / op2;
        }

        return result;
    }
}

2.参考网上资料以及自己的对代码的理解后得出MyBC.java

public class MyBC {
    private Stack theStack;
    private String input;
    private String output = "";
    public MyBC(String in) {
        input = in;
        int stackSize = input.length();
        theStack = new Stack(stackSize);
    }
    public String doTrans() {
        for (int j = 0; j < input.length(); j++) {
            char ch = input.charAt(j);
            switch (ch) {
                case '+':
                case '-':
                    gotOper(ch, 1);
                    break;
                case '*':
                case '/':
                    gotOper(ch, 2);
                    break;
                case '(':
                    theStack.push(ch);
                    break;
                case ')':
                    gotParen(ch);
                    break;
                default:
                    output = output + ch;
                    break;
            }
        }
        while (!theStack.isEmpty()) {
            output = output + theStack.pop();
        }
        return output;
    }
    public void gotOper(char opThis, int prec1) {
        while (!theStack.isEmpty()) {
            char opTop = theStack.pop();
            if (opTop == '(') {
                theStack.push(opTop);
                break;
            }
            else {
                int prec2;
                if (opTop == '+' || opTop == '-')
                    prec2 = 1;
                else
                    prec2 = 2;
                if (prec2 < prec1) {
                    theStack.push(opTop);
                    break;
                }
                else
                    output = output + opTop;
            }
        }
        theStack.push(opThis);
    }
    public void gotParen(char ch){
        while (!theStack.isEmpty()) {
            char chx = theStack.pop();
            if (chx == '(')
                break;
            else
                output = output + chx;
        }
    }
    class Stack {
        private int maxSize;
        private char[] stackArray;
        private int top;
        public Stack(int max) {
            maxSize = max;
            stackArray = new char[maxSize];
            top = -1;
        }
        public void push(char j) {
            stackArray[++top] = j;
        }
        public char pop() {
            return stackArray[top--];
        }
        public char peek() {
            return stackArray[top];
        }
        public boolean isEmpty() {
            return (top == -1);
        }
    }
}

3.运行后得到实验截图

三、实验截图：


四、码云链接：

MyBC：https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/blob/master/实验5/MyBC.java
MyDC：https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/blob/master/实验5/MyDC.java
MyDCTester：https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/blob/master/实验5/MyDCTester.java

任务二：

一、实验要求

结对编程：
1人负责客户端，一人负责服务器
0. 注意责任归宿，要会通过测试证明自己没有问题

  1. 基于Java Socket实现客户端/服务器功能，传输方式用TCP
  2. 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
  3. 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
  4. 客户端显示服务器发送过来的结果
  5. 上传测试结果截图和码云链接

二、实验步骤

1、首先建立server

import java.net.*;
import java.io.*;

public class Server{
    public static void main(String srgs[]) throws Exception
    {
        ServerSocket sc = null;
        Socket socket=null;
        try
        {
            MyDC evaluator = new MyDC();

            sc= new ServerSocket(10000);//创建服务器套接字
            System.out.println("端口号:" + sc.getLocalPort());
            System.out.println("服务器成功启动，等待客户端呼叫");
            socket = sc.accept();   //等待客户端连接
            System.out.println("已经建立连接");//获得网络输入流对象的引用
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));//获得网络输出流对象的引用
            PrintWriter out=new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);
            String aline2=in.readLine();
            System.out.println("客户端发来的信息为："+aline2);

            int ans = evaluator.evaluate(aline2);
            out.println(ans);
            System.out.println("result = "+ans);
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    //十六进制和十进制转换
    public static byte[] parseHexStr2Byte(String hexStr)
    {
        if (hexStr.length() < 1)
            return null;
        byte[] result = new byte[hexStr.length()/2];
        for (int i = 0;i< hexStr.length()/2; i++)
        {
            int high = Integer.parseInt(hexStr.substring(i*2, i*2+1 ), 16);
            int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);
            result[i] = (byte) (high * 16 + low);
        }
        return result;
    }
}

2.再建立client。

import java.net.*;
import java.io.*;
public class Client
{
    public static void main(String srgs[]) throws Exception
    {
        try
        {
            // 1、创建客户端Socket，指定服务器地址和端口
            Socket socket=new Socket("127.0.0.1",10000);
            System.out.println("客户端成功启动，等待服务器应答");
            // 2、获取输出流，向服务器端发送信息
            // 向本机的10001端口发出客户请求
            System.out.println("请输入中缀表达式：");
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            // 由系统标准输入设备构造BufferedReader对象
            PrintWriter write = new PrintWriter(socket.getOutputStream());
            // 由Socket对象得到输出流，并构造PrintWriter对象
            //3、获取输入流，并读取服务器端的响应信息
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            // 由Socket对象得到输入流，并构造相应的BufferedReader对象
            String readline, infix, expression;
            readline = br.readLine(); // 从系统标准输入读入一字符串
            MyBC theTrans = new MyBC(readline);
            infix = theTrans.doTrans();
            StringBuilder newInfix = new StringBuilder(infix.replace(" ",""));
            for (int i = 1; i < infix.length()+(i+1)/2 ; i=i+2) {
                newInfix.insert(i," ");
            }
            System.out.println("后缀表达式：" + newInfix);
            expression=newInfix.toString();

            while (!readline.equals("end")) {
                // 若从标准输入读入的字符串为 "end"则停止循环
                write.println(expression);
                // 将从系统标准输入读入的字符串输出到Server
                write.flush();
                // 刷新输出流，使Server马上收到该字符串
                System.out.println("收到服务器的消息:" + in.readLine());
                // 从Server读入一字符串，并打印到标准输出上
                readline = br.readLine(); // 从系统标准输入读入一字符串
            } // 继续循环
            //4、关闭资源
            write.close(); // 关闭Socket输出流
            in.close(); // 关闭Socket输入流
            socket.close(); // 关闭Socket
        }
        catch (Exception e)
        {
            System.out.println(e);//输出异常
        }
        finally
        {

        }

    }
}

3、先在同一个电脑上先运行server.java，再运行client.java，得到如下实验截图。

三、实验截图：
四、码云链接 ：https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/tree/master/实验5

任务三：

一、实验要求：

加密结对编程：1人负责客户端，一人负责服务器
0. 注意责任归宿，要会通过测试证明自己没有问题

  1. 基于Java Socket实现客户端/服务器功能，传输方式用TCP
  2. 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算法加密后通过网络把密文发送给服务器
  3. 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
  4. 客户端显示服务器发送过来的结果
  5. 上传测试结果截图和码云链接

二、实验步骤

1.首先创建密钥

import java.io.*;
import java.security.*;
public class Skey_kb{
    public static void main(String args[]) throws Exception{
        FileInputStream f=new FileInputStream("key1.dat");
        ObjectInputStream b=new ObjectInputStream(f);
        Key k=(Key)b.readObject( );
        byte[ ] kb=k.getEncoded( );
        FileOutputStream  f2=new FileOutputStream("keykb1.dat");
        f2.write(kb);
        // 打印密钥编码中的内容
        for(int i=0;i<kb.length;i++){
            System.out.print(kb[i]+",");
        }
    }
}

import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import java.io.*;
import java.security.*;

public class Skey {
    public static void main(String args[]) throws Exception {
        KeyGenerator kg = KeyGenerator.getInstance("DESede");
        kg.init(168);
        SecretKey k = kg.generateKey();
        FileOutputStream f = new FileOutputStream("key1.txt");
        ObjectOutputStream b = new ObjectOutputStream(f);
        b.writeObject(k);
    }
}

2、建立服务器server

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class Server_2 {
    public static void main(String args[]) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try {
            serverForClient = new ServerSocket(3001);
        } catch (IOException e1) {
            System.out.println(e1);
        }
        try {
            System.out.println("等待客户呼叫");
            socketOnServer = serverForClient.accept(); //堵塞状态，除非有客户呼叫
            System.out.println("客户已连接");
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());
            String leng = in.readUTF(); // in读取信息，堵塞状态
            byte ctext[] = new byte[Integer.parseInt(leng)];
            for (int i = 0;i<Integer.parseInt(leng);i++) {
                 String temp = in.readUTF();
                 ctext[i] = Byte.parseByte(temp);
            }
            // 获取密钥
            FileInputStream f2 = new FileInputStream("keykb1.txt");
            int num2 = f2.available();
            byte[] keykb = new byte[num2];
            f2.read(keykb);
            SecretKeySpec k = new SecretKeySpec(keykb, "DESede");
            // 解密
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            byte[] ptext = cp.doFinal(ctext);
            System.out.println("后缀表达式已被解密：");
            for (int i = 0; i < ptext.length; i++) {
                System.out.print(ptext[i] + ",");
            }
            System.out.println("");
            // 显示明文
            String p = new String(ptext, "UTF8");
            System.out.println("服务器收到客户的请求:计算后缀表达式" + p);
            out.writeUTF(MyDC.jisuan(new StringBuffer(p))+"");
        } catch (Exception e) {
            System.out.println("客户已断开" + e);
        }
    }
}

3.建立client

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

public class Client_2 {
    public static void main(String args[]) {
        Socket mysocket;
        DataInputStream in = null;
        DataOutputStream out = null;
        Scanner scanner = new Scanner(System.in);
        String str;
        try {
            FileInputStream f = new FileInputStream("key1.txt");
            ObjectInputStream b = new ObjectInputStream(f);
            Key k = (Key) b.readObject();
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.ENCRYPT_MODE, k);
            mysocket = new Socket("192.168.1.125", 3001);
            in = new DataInputStream(mysocket.getInputStream());
            out = new DataOutputStream(mysocket.getOutputStream());
            System.out.println("已连接服务器，请输入中缀表达式：");
            str = scanner.nextLine();
            byte ptext[] = MyBC.tran(new StringBuffer(str)).toString().getBytes("UTF-8");
            byte ctext[] = cp.doFinal(ptext);
            System.out.println("后缀表达式已被加密：");
            for (int i = 0; i < ctext.length; i++) {
                System.out.print(ctext[i] + ",");
            }
            System.out.println("");
            out.writeUTF(ctext.length + "");
            for (int i = 0; i < ctext.length; i++) {
                out.writeUTF(ctext[i] + "");
                //System.out.print();
            }
            String s = in.readUTF();   //in读取信息，堵塞状态
            System.out.println("客户收到服务器的回应:" + s);
        } catch (Exception e) {
            System.out.println("服务器已断开" + e);
        }
    }
}

4.运行后得到如下截图

三、实验截图：

四、码云链接：https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/tree/master/实验5

任务四：

一、实验要求：密钥分发结对编程：1人负责客户端，一人负责服务器
0. 注意责任归宿，要会通过测试证明自己没有问题

  1. 基于Java Socket实现客户端/服务器功能，传输方式用TCP
  2. 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发送给服务器
  3. 客户端和服务器用DH算法进行3DES或AES算法的密钥交换
  4. 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
  5. 客户端显示服务器发送过来的结果
  6. 上传测试结果截图和码云链接

二、实验步骤
1、建立dh算法代码：

/**
 * @20165213zqh
 */
import java.io.*;
import java.math.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import javax.crypto.interfaces.*;

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
    };
    private static final BigInteger skip1024Modulus = new BigInteger(1, skip1024ModulusBytes);
    private static final BigInteger skip1024Base = BigInteger.valueOf(2);
    public static void fun(String s1,String s2) 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();
        FileOutputStream  f1=new FileOutputStream(s1);
        ObjectOutputStream b1=new  ObjectOutputStream(f1);
        b1.writeObject(pbk);        FileOutputStream  f2=new FileOutputStream(s2);
        ObjectOutputStream b2=new  ObjectOutputStream(f2);
        b2.writeObject(prk);
    }
}

2.建立KeyAgree.java

/**
 * @20165213zqh
 */
import java.io.*;
import java.math.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import javax.crypto.interfaces.*;

public class KeyAgree{
    public static void fun(String s1,String s2) throws Exception{
        // 读取对方的DH公钥
        FileInputStream f1=new FileInputStream(s1);
        ObjectInputStream b1=new ObjectInputStream(f1);
        PublicKey  pbk=(PublicKey)b1.readObject( );
//读取自己的DH私钥
        FileInputStream f2=new FileInputStream(s2);
        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.txt");
        fsb.write(sb);
    }
}

3.建立server

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

public class Server_3 {
    public static void main(String args[]) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try {
            serverForClient = new ServerSocket(3001);
        } catch (IOException e1) {
            System.out.println(e1);
        }
        try {
            System.out.println("等待客户呼叫");
            socketOnServer = serverForClient.accept(); //堵塞状态，除非有客户呼叫
            System.out.println("客户已连接");
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());

            Key_DH.fun("Spub.txt","Spri.txt");
            int len = Integer.parseInt(in.readUTF());
            byte np[] = new byte[len];
            for (int i = 0;i<len;i++) {
                String temp = in.readUTF();
                np[i] = Byte.parseByte(temp);
            }
            ObjectInputStream ois = new ObjectInputStream (new ByteArrayInputStream (np));
            Key k2 = (Key)ois.readObject();;
            FileOutputStream f2 = new FileOutputStream("Cpub.txt");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k2);

            FileInputStream fp = new FileInputStream("Spub.txt");
            ObjectInputStream bp = new ObjectInputStream(fp);
            Key kp = (Key) bp.readObject();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(kp);
            byte[] kb = baos.toByteArray();
            out.writeUTF(kb.length + "");
            for (int i = 0; i < kb.length; i++) {
                out.writeUTF(kb[i] + "");
            }

            KeyAgree.fun("Cpub.txt","Spri.txt");

            String leng = in.readUTF(); // in读取信息，堵塞状态
            byte ctext[] = new byte[Integer.parseInt(leng)];
            for (int i = 0;i<Integer.parseInt(leng);i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            // 获取密钥
            FileInputStream f = new FileInputStream("sb.txt");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密钥：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+",");
            }
            System.out.println("");
            SecretKeySpec k = new SecretKeySpec(keysb, "DESede");
            // 解密
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            byte[] ptext = cp.doFinal(ctext);
            System.out.println("后缀表达式已被解密：");
            for (int i = 0; i < ptext.length; i++) {
                System.out.print(ptext[i] + ",");
            }
            System.out.println("");
            // 显示明文
            String p = new String(ptext, "UTF8");
            System.out.println("服务器收到客户的请求:计算后缀表达式" + p);
            out.writeUTF(MyDC.jisuan(new StringBuffer(p))+"");
        } catch (Exception e) {
            System.out.println("客户已断开" + e);
        }
    }
}

4、建立客户端 ，由结对编程伙伴完成。


5、运行程序得到结果。

三、实验截图：

四、码云链接：https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/tree/master/实验5

任务五

一、实验要求:

完整性校验结对编程：1人负责客户端，一人负责服务器
0. 注意责任归宿，要会通过测试证明自己没有问题

  1. 基于Java Socket实现客户端/服务器功能，传输方式用TCP
  2. 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
  3. 客户端和服务器用DH算法进行3DES或AES算法的密钥交换
  4. 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
  5. 客户端显示服务器发送过来的结果
  6. 上传测试结果截图和码云链接

二、实验步骤：

import java.security.*;
public class DigestPass{
    public static String fun(String ss) throws Exception{
        String x=ss;
        MessageDigest m=MessageDigest.getInstance("MD5");
        m.update(x.getBytes("UTF8"));
        byte s[ ]=m.digest( );
        String result="";
        for (int i=0; i<s.length; i++){
            result+=Integer.toHexString((0x000000ff & s[i]) |
                    0xffffff00).substring(6);
        }
        return result;
    }
}

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 Server_4 {
    public static void main(String args[]) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try {
            serverForClient = new ServerSocket(3001);
        } catch (IOException e1) {
            System.out.println(e1);
        }
        try {
            System.out.println("等待客户呼叫");
            socketOnServer = serverForClient.accept(); //堵塞状态，除非有客户呼叫
            System.out.println("客户已连接");
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());

            Key_DH.fun("Spub.txt","Spri.txt");
            int len = Integer.parseInt(in.readUTF());
            byte np[] = new byte[len];
            for (int i = 0;i<len;i++) {
                String temp = in.readUTF();
                np[i] = Byte.parseByte(temp);
            }
            ObjectInputStream ois = new ObjectInputStream (new ByteArrayInputStream(np));
            Key k2 = (Key)ois.readObject();;
            FileOutputStream f2 = new FileOutputStream("Cpub.txt");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k2);

            FileInputStream fp = new FileInputStream("Spub.txt");
            ObjectInputStream bp = new ObjectInputStream(fp);
            Key kp = (Key) bp.readObject();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(kp);
            byte[] kb = baos.toByteArray();
            out.writeUTF(kb.length + "");
            for (int i = 0; i < kb.length; i++) {
                out.writeUTF(kb[i] + "");
            }

            KeyAgree.fun("Cpub.txt","Spri.txt");

            String leng = in.readUTF(); // in读取信息，堵塞状态
            byte ctext[] = new byte[Integer.parseInt(leng)];
            for (int i = 0;i<Integer.parseInt(leng);i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            String check = in.readUTF();
            // 获取密钥
            FileInputStream f = new FileInputStream("sb.txt");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密钥：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+",");
            }
            System.out.println("");
            SecretKeySpec k = new SecretKeySpec(keysb, "DESede");
            // 解密
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            byte[] ptext = cp.doFinal(ctext);
            System.out.println("后缀表达式已被解密：");
            for (int i = 0; i < ptext.length; i++) {
                System.out.print(ptext[i] + ",");
            }
            System.out.println("");
            // 显示明文
            String p = new String(ptext, "UTF8");
            String pMd5 = DigestPass.fun(p);
            System.out.println("解密后明文的MD5值："+pMd5);
            if (pMd5.equals(check)){
                System.out.println("和客户端的MD5值一致");
                System.out.println("服务器收到客户的请求:计算后缀表达式" + p);
                out.writeUTF(MyDC.jisuan(new StringBuffer(p))+"");
            }
            else {
                System.out.println("警告：和客户端的MD5值不一致！");
            }
        } catch (Exception e) {
            System.out.println("客户已断开" + e);
        }
    }
}

3、client由结对伙伴完成，运行程序。

三、实验截图：

四、码云链接：https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/tree/master/实验5

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原文地址：https://www.cnblogs.com/xiaozhuzqh/p/9100997.html