20135236贾瑗—实验五

package nine;
import java.net.*;
import java.io.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import javax.crypto.interfaces.*;
import java.security.interfaces.*;
import java.math.*;
public class ComputeTCPServer{
        public static void main(String srgs[]) throws Exception 
        {
        ServerSocket sc = null;
        Socket socket=null;
            try 
            {
            sc= new ServerSocket(8080);//创建服务器套接字
            System.out.println("端口号:" + sc.getLocalPort());
            System.out.println("服务器已经启动...");
            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);
            
            //使用服务器端RSA的私钥对DES的密钥进行解密
            String aline2=in.readLine();
            BigInteger c=new BigInteger(aline2);
            FileInputStream f=new FileInputStream("Skey_RSA_priv.dat");
            ObjectInputStream b=new ObjectInputStream(f);
            RSAPrivateKey prk=(RSAPrivateKey)b.readObject( );
            
            BigInteger d=prk.getPrivateExponent();
            BigInteger n=prk.getModulus();
            BigInteger m=c.modPow(d,n);
            byte[] keykb=m.toByteArray();
            
            //使用DES对密文进行解密
            String aline=in.readLine();//读取客户端传送来的数据
            byte[] ctext=parseHexStr2Byte(aline);
            Key k=new  SecretKeySpec(keykb,"DESede");
            Cipher cp=Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            byte []ptext=cp.doFinal(ctext);    
            String p=new String(ptext,"UTF8");
            System.out.println("从客户端接收到信息为："+p); //通过网络输出流返回结果给客户端
        
        //使用Hash函数检测明文完整性        
        String aline3=in.readLine();
        String x=p;
        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); 
        
        if(aline3.equals(result))
        {
            System.out.println("匹配成功");
        }
        
            out.println("匹配成功");
            out.close();
            in.close();
            sc.close();
            } catch (Exception e) {
            System.out.println(e);
        } 
    }
        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;  
    }  
    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();  
    }  
    
}