r9U03Q0S

1import java.net.*;
2import java.io.*;
3import java.security.InvalidAlgorithmParameterException;
4import java.security.InvalidKeyException;
5import java.security.NoSuchAlgorithmException;
6import javax.crypto.*;
7import javax.crypto.spec.IvParameterSpec;
8import javax.crypto.spec.SecretKeySpec;
9
10public class Server{
11    public static void main(String args[]){
12        int number=0;
13        try{
14            int serverPort = 4567;
15            ServerSocket listenSocket = new ServerSocket(serverPort);
16            while(true) {
17                Socket clientSocket = listenSocket.accept();
18                new Connection(clientSocket,number);
19                number++;
20            }
21        } catch(IOException e) {
22            System.out.println("Listen:" + e.getMessage());
23        }
24    }
25}
26
27class Connection extends Thread {
28    DataInputStream in;
29    DataOutputStream out;
30    Socket clientSocket;
31    int number;
32
33    public Connection (Socket aClientSocket,int clientNumber) {
34        try{
35            number=clientNumber;
36            clientSocket = aClientSocket;
37            in = new DataInputStream(clientSocket.getInputStream());
38            out = new DataOutputStream(clientSocket.getOutputStream());
39            this.start();
40        }catch(IOException e){System.out.println("Connection:" + e.getMessage());}
41    }
42
43    public void run(){
44        try{
45            while(true){
46
47                InputStream is = in;
48
49                //key
50                byte [] key = {1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4};
51                SecretKey secretKey = new SecretKeySpec(key, 0, key.length, "AES");
52
53                //nonce
54                //receives IV in plaintext
55                byte[] nonce=new byte[16];
56                is.read(nonce);
57                IvParameterSpec iv = new IvParameterSpec(nonce);
58
59
60                Cipher c = Cipher.getInstance("AES/CTR/PKCS5Padding");
61                c.init(Cipher.DECRYPT_MODE, secretKey, iv);
62
63
64                CipherInputStream cis = new CipherInputStream(is, c);
65                int text;
66                while((text=cis.read())!=-1) {
67                    System.out.print((char)text);
68
69                }
70            }
71        }
72        catch (NoSuchPaddingException e) {
73            e.printStackTrace();
74        }
75        catch (NoSuchAlgorithmException e) {
76            e.printStackTrace();
77        }
78        catch (InvalidKeyException e) {
79            e.printStackTrace();
80        }
81        catch (InvalidAlgorithmParameterException e) {
82            e.printStackTrace();
83        }
84        catch (IOException e) {
85            e.printStackTrace();
86        }
87    }
88}