Experiment five--java network programming and security

Java's second experiment--java object-oriented programming

Beijing Institute of Electronic Technology

Lab Report

Course: Java Programming Class: 1352 name: Linhan Kam No.: 20135213

Score: Instructor: Lou Jia Peng Experimental Date: 2015.6.11

Experiment level: Preview degree: Experiment time: 15:30~22:00

Instrument Group: 13 Compulsory/elective: Elective experiment number: 5

Experiment Name: Java Network programming and security

Experimental purposes and requirements:

Objective: 1. Master the socket program writing;

2. Mastering the use of cryptographic technology;

3. Design Safety

Requirements: 1. Complete information encryption

2. Send information after encryption

Experimental instrument:

Name	Model	Number
Pc	Acer	1

Experiment Code

Package server;

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 Servert {

public static void Main (String args[]) throws Exception {

ServerSocket link = null;

Socket socket = NULL;

try {

link = new ServerSocket (8080);//Create a server socket

SYSTEM.OUT.PRINTLN ("Port number:" + link.getlocalport ());

SYSTEM.OUT.PRINTLN ("Server has started ...");

Socket = Link.accept (); Waiting for client connections

SYSTEM.OUT.PRINTLN ("Connection already established");

Get a reference to a network input stream object

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

Get a reference to a network output stream object

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

Decryption of DES keys using the private key of the server-side RSA

String line = In.readline ();

BigInteger cipher = new BigInteger (line);

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 ();//mod n

BigInteger m = Cipher.modpow (d, N);//m=d (mod n)

byte[] keykb = M.tobytearray ();

Use Des to decrypt ciphertext

String ReadLine = In.readline ();//Read data sent by the client

FileInputStream F2 = new FileInputStream ("Keykb1.dat");

int num2 = f2.available ();

byte[] Ctext = Parsehexstr2byte (ReadLine);

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");//Encoding conversion

System.out.println ("received from the client information:" + P); Print decryption results

Detecting plaintext integrity using the hash function

String Aline3 = In.readline ();

String x = p;

MessageDigest m2 = messagedigest.getinstance ("MD5");//Use MD5 algorithm to return the MessageDigest object that implements the specified digest algorithm

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 ("match success");

}

Out.println ("match success");

Out.close ();

In.close ();

Link.close ();

} catch (Exception e) {

System.out.println (e);

}

}

Binary conversion to 16, prevents byte[] data loss caused by conversion of number to string type

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 ());//Convert lowercase letters in a string to uppercase letters and then add them to the string

}

return sb.tostring ();

}

Converting 16 binary to binary

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 * + low);

}

return result;

}

}

Measured operation diagram:

Experimental summary

1, pair-coded PSP time

step	time-consuming min	percent
demand analysis	60	20%
design	60	20%
code implementation	120	40% 
test	30	10%
Analysis summary	30	10%

2, encountered problems and solutions:

(1) IP address does not look up

Workaround: Open run, enter cmd, and enter ipconfig

(2) Always show connection timeout

Solution: One person connected to WiFi, then open the free WiFi network, the connection is successful.

3. Summary of Feelings

When solving practical problems with the program, the collaborators can find the mistakes they can't find, and propose different solutions and expand their thinking. The last experiment is a little bit difficult, although the basic code is given, but the network connection between computers, code combinations and other issues are still very tricky. Very test ability.

Experiment five--java network programming and security