实验五

import java.net.*;
import java.io.*;
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.spec.*;
import javax.crypto.interfaces.*;
import java.security.interfaces.*;
import java.math.*;

public class TCP_Client 
{
    public static void main(String srgs[]) throws Exception 
    {
        try 
        {
            KeyGenerator kg = KeyGenerator.getInstance("DESede");
            kg.init(168);
            SecretKey k = kg.generateKey();
            byte[] ptext2 = k.getEncoded();

            // 创建连接特定服务器的指定端口的Socket对象
            Socket socket = new Socket("192.168.253.1", 8030);//这里输入的是服务器的ip地址和端口号，端口号要注意和服务器保持一致。
            
            // 获得从服务器端来的网络输入流
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            
            // 获得从客户端向服务器端输出数据的网络输出流
            PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
            
            // 创建键盘输入流，以便客户端从键盘上输入信息
            BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));

            //RSA算法，使用服务器端的公钥对DES的密钥进行加密
            FileInputStream f3 = new FileInputStream("Skey_RSA_pub.dat");
            ObjectInputStream b2 = new ObjectInputStream(f3);
            RSAPublicKey pbk = (RSAPublicKey) b2.readObject();
            BigInteger e = pbk.getPublicExponent();
            BigInteger n = pbk.getModulus();
            BigInteger m = new BigInteger(ptext2);
            BigInteger c = m.modPow(e, n);
            String cs = c.toString();
            out.println(cs); // 通过网络将加密后的秘钥传送到服务器

            //用DES加密明文得到密文
            System.out.print("请输入待发送的数据：");
            String s = stdin.readLine(); // 从键盘读入待发送的数据
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.ENCRYPT_MODE, k);
            byte ptext[] = s.getBytes("UTF8");
            byte ctext[] = cp.doFinal(ptext);
            String str = parseByte2HexStr(ctext);
            out.println(str); // 通过网络将密文传送到服务器

            // 将客户端明文的Hash值传送给服务器
            String x = s;
            MessageDigest m2 = MessageDigest.getInstance("MD5");
            m2.update(x.getBytes());
            byte a[] = m2.digest();
            String result = "";
            for (int i = 0; i < a.length; i++) 
            {
                result += Integer.toHexString((0x000000ff & a[i]) | 0xffffff00).substring(6);
            }
            System.out.println(result);
            out.println(result);//通过网络将明文的Hash函数值传送到服务器

            str = in.readLine();// 从网络输入流读取结果
            System.out.println("从服务器接收到的结果为：" + str); // 输出服务器返回的结果
        } 
        catch (Exception e) 
        {
            System.out.println(e);//输出异常
        } 
        finally 
        {

        }

    }

    public static String parseByte2HexStr(byte buf[])
    {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < buf.length; i++)
        {
            String hex = Integer.toHexString(buf[i] & 0xFF);
            if (hex.length() == 1) 
            {
                hex = ‘0‘ + hex;
            }
            sb.append(hex.toUpperCase());
        }
        return sb.toString();
    }

    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;
    }
}