Fourth Java Lab Report

Beijing Institute of Electronic Technology (BESTI)

Lab Report

Course: Java class: 1353 Name: Guo Haoxue No.: 20135327

Score: Instructor: Lou Jia Peng Experimental Date: 2015.6.9

Experiment level: Preview degree: Experiment time: 15:30~18:00

Instrument Group: 20 Compulsory/elective: Elective experiment number: 04

Experiment Name: Network programming and security

Experimental purposes and requirements:

1. Mastering the Java Network programming method;

2. Master the method of Java security programming;

3. Can be used in a comprehensive range of technologies.

Experimental instrument:

Name	Model	Number
Lenovo	V480	1
Lenovo	YOga 13	1

Statistics for PSP (Personal software Process) time

Steps	Time-consuming (min)	Percentage
Demand analysis	10	4.17%
Design	60	25%
Code implementation	120	50%
Test	30	12.5%
Analysis Summary	20	8.33%

First, experiment contents and steps

Lab Staff:

Client: 20135327 Guo Hao

server:20135329 Li Haiyin http://www.cnblogs.com/haikong/

Experimental content:

1 Writing network communication programs (TCP-based)

2 Encrypt the communication content using the Symmetric DES encryption algorithm

3 using asymmetric algorithms to distribute the keys used in symmetric encryption

4 Summary calculation and verification of the communication content

5 Other security measures

Experimental steps:

1. Client-side Message des encryption (using RSA public key to encrypt des keys)

2. The server accepts the information and decrypts it (using the RSA private key)

3. Verifying Information integrity

Experiment Code:

Import java.math.*;

Import java.net.*;
Import Java.security.Key;

Import java.io.*;

Import Javax.crypto.Cipher;

public class Client {

public static void Main (String srgs[]) {

try {

Socket socket = new Socket ("172.30.113.2", 4421);

BufferedReader in = new BufferedReader (New InputStreamReader (Socket.getinputstream ()));

PrintWriter out = new PrintWriter (new BufferedWriter (New OutputStreamWriter (Socket.getoutputstream ())), true);

BufferedReader stdin = new BufferedReader (new InputStreamReader (system.in));

System.out.print ("Please lose the data sent:");

String s = stdin.readline ();

String cs = new SEnc (). ENC (s);

SYSTEM.OUT.PRINTLN ("Ciphertext sent to the server:" + cs);

String ck = new Enc_rsa (). ENC (s);

SYSTEM.OUT.PRINTLN ("The encryption key sent to the server is:" + ck);

String result = Digestcalc.hash (s);

System.out.println ("MD5:" + result);

Out.println (CK);

OUT.PRINTLN (CS);

OUT.PRINTLN (result);

} catch (Exception e) {

System.out.println (e);

} finally {

}

}

}

Experiment:

Second, the problems encountered in the experiment and the solutions

1. Send after des encrypted ciphertext is the way to convert it to a string, where the client is using the ToString () function, the server is using the GetBytes () function, after the transmission of ciphertext error. In the last discussion, binary to hexadecimal output cipher text is used. The code is as follows:

public static String bytestohexstring (byte[] src) {
StringBuilder StringBuilder = new StringBuilder ("");
if (src = = NULL | | src.length <= 0) {
return null;
}
for (int i = 0; i < src.length; i++) {
int v = src[i] & 0xFF;
String HV = integer.tohexstring (v);
if (Hv.length () < 2) {
Stringbuilder.append (0);
}
Stringbuilder.append (HV);
}
return stringbuilder.tostring ();
}

2. Two computers have been unable to connect

In the lab we started with our own IPV4 address from the bedroom LAN and then showed the connection timeout.

We think it may be that the two computers are not in the same network without a successful link, try to use a computer to connect to the network and WiFi to another computer, and then connect two computers again, finally connected successfully.

Do not know why, it may be because of the local area network!

Fourth Java Lab Report