Java Socket Programming with AES encryption

[rayoflight]

This is how my test program works.

Server will encrypt some text and sends it over to the client.
The client will then decrypts it.

However I have some problem decrypting it. When I play around with the key and the plaintext, sometime it is able to decrypt. I think it should be some ASCII character problems.

Right now, I am using out.writeUTF(ne w String(encrypte d)); and on this other side I use in.readUTF() to get the string. Lastly, I convert the string to byte for decryption.

Is there anyway to fix this problem? Basically, what and how do I send the ciphertext over and how can I decrypt properly on the other side.

Here are my codes, thanks in advance..

Server:

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

import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;

public class RealEchoServer{
    public static void main(String[] args ){
        int i = 1;
        try{
             ServerSocket s = new ServerSocket(9003);

             for (;;){
                 Socket incoming = s.accept( );
                 System.out.println("Spawning " + i);
                 new RealEchoHandler(incoming, i).start();
                 i++;
             }
        } catch (Exception e){ System.out.println(e); }
    }
}

class RealEchoHandler extends Thread{
	DataInputStream in;
	DataOutputStream out;
	private Socket incoming;
    private int counter;

    public RealEchoHandler(Socket i, int c){
        incoming = i;
        counter = c;
    }

    public void run(){
        try {


			String key1 = "1234567812345678"; 
	      	byte[] key2 = key1.getBytes();
	      	SecretKeySpec secret = new SecretKeySpec(key2, "AES");
			String msg = "Singapore Malaysia Japan India Indonesia HongKong Taiwan China England";
			Cipher cipher = Cipher.getInstance("AES");        
	   	 	cipher.init(Cipher.ENCRYPT_MODE, secret);
	   		byte[] encrypted = cipher.doFinal(msg.getBytes());

            in = new DataInputStream(incoming.getInputStream());
			out = new DataOutputStream(incoming.getOutputStream());

            boolean done = false;
            String str="";
            out.writeUTF("Connected!\n");
            out.flush();
            while (!done){
				out.writeUTF(">");
				out.flush();
                str = in.readUTF();
                System.out.println(in+":"+str);
                if (str == null)
                    done = true;
                else{
                	System.out.println("Sending Ciphertext : " + new String(encrypted));
                    out.writeUTF(new String(encrypted));
                    out.flush();
                }
            }
            incoming.close();
         } catch (Exception e){
             System.out.println(e);
         }
    }
}

Client:

import java.io.*;
import java.net.*;
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.util.*;

class RealSocketTest{
	public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
	
		String str = "";
		String str2 = "";
		DataOutputStream out;
		DataInputStream in;

		try {
		    Socket t = new Socket("127.0.0.1", 9003);
            in = new DataInputStream(t.getInputStream());
            out = new DataOutputStream(t.getOutputStream());
            BufferedReader br = new BufferedReader (new InputStreamReader(System.in));

            boolean more = true;
			System.out.println(in.readUTF());	

            while (more) {
				str = in.readUTF();
			    System.out.print(str);
                str2 = br.readLine();
				out.writeUTF(str2);
                out.flush();
				str = in.readUTF();
				
				System.out.println("Encrypted Info: " + str);
				
				try {

					String key1 = "1234567812345678"; 
	      			byte[] key2 = key1.getBytes();
	      			SecretKeySpec secret = new SecretKeySpec(key2, "AES");
	
					Cipher cipher = Cipher.getInstance("AES");        
	   	 	
					cipher.init(Cipher.DECRYPT_MODE, secret);
					byte[] decrypted = cipher.doFinal(str.getBytes());
					System.out.println("Decrypted Info: " + new String(decrypted));
				}
		        catch(BadPaddingException e){
		        	System.out.println("Wrong Key!");
				}
				catch(InvalidKeyException f) {
					System.out.println("Invalid Key!");
				}
            }
		} 
        catch(IOException e){
        	System.out.println("Error");
		}
	}
}

[Nepomuk]

This is how my test program works.

Server will encrypt some text and sends it over to the client.
The client will then decrypts it.

However I have some problem decrypting it. When I play around with the key and the plaintext, sometime it is able to decrypt. I think it should be some ASCII character problems.

Hi!
You say, sometimes you can decrypt? So I guess, sometimes you can't. Can you give us an example for a few keys and plaintexts that work and some that don't?

Greetings,
Nepomuk

[rayoflight]

Thanks, that answers my question