xWwyUU1Y

1import java.net.*;
2import java.io.*;
3import javax.crypto.*;
4import javax.crypto.spec.IvParameterSpec;
5import javax.crypto.spec.SecretKeySpec;
6import java.security.InvalidAlgorithmParameterException;
7import java.security.InvalidKeyException;
8import java.security.MessageDigest;
9import java.security.NoSuchAlgorithmException;
10
11public class Server{
12    public static void main(String args[]){
13        int number=0;
14        try{
15            int serverPort = 4567;
16            ServerSocket listenSocket = new ServerSocket(serverPort);
17            while(true) {
18                Socket clientSocket = listenSocket.accept();
19                new Connection(clientSocket,number);
20                number++;
21            }
22        } catch(IOException e) {
23            System.out.println("Listen:" + e.getMessage());
24        }
25    }
26}
27
28class Connection extends Thread {
29    DataInputStream in;
30    DataOutputStream out;
31    Socket clientSocket;
32    int number;
33
34    public Connection (Socket aClientSocket,int clientNumber) {
35        try{
36            number=clientNumber;
37            clientSocket = aClientSocket;
38            in = new DataInputStream(clientSocket.getInputStream());
39            out = new DataOutputStream(clientSocket.getOutputStream());
40            this.start();
41        }catch(IOException e){System.out.println("Connection:" + e.getMessage());}
42    }
43
44    public void run(){
45        try{
46            while(true){
47                //key
48                byte [] key = {1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4};
49
50                //hash function and new keys
51                MessageDigest md = MessageDigest.getInstance("SHA-256");
52
53                byte [] byte1 = {1};
54                byte [] aux1 = concat(key, byte1);
55                byte [] hash1= md.digest(aux1);
56                SecretKey k1 = new SecretKeySpec(hash1, 0, hash1.length, "AES");
57
58                byte [] byte2 = {2};
59                byte [] aux2 = concat(key, byte2);
60                byte [] hash2= md.digest(aux2);
61                SecretKey k2 = new SecretKeySpec(hash2, 0, hash2.length, "AES");
62
63                //message authentication code
64                Mac mac = Mac.getInstance("HmacSHA256");
65                mac.init(k2);
66                int nSeq = 0;
67
68                //nonce - receives IV in plaintext
69                byte[] nonce=new byte[16];
70                in.read(nonce);
71                IvParameterSpec iv = new IvParameterSpec(nonce);
72
73                //D(m, k1) = c - só se decifra se a autenticação do mac correr bem
74                Cipher c = Cipher.getInstance("AES/CTR/PKCS5Padding");
75                c.init(Cipher.DECRYPT_MODE, k1, iv);
76                int text;
77
78                while(true){
79                    String ciphertext = in.readUTF();
80                    System.out.println(ciphertext);
81
82                    String t = in.readUTF();
83                    System.out.println(t);
84                }
85
86
87            }
88        }
89        catch (NoSuchPaddingException e) {
90            e.printStackTrace();
91        }
92        catch (NoSuchAlgorithmException e) {
93            e.printStackTrace();
94        }
95        catch (InvalidKeyException e) {
96            e.printStackTrace();
97        }
98        catch (InvalidAlgorithmParameterException e) {
99            e.printStackTrace();
100        }
101        catch (IOException e) {
102            e.printStackTrace();
103        }
104    }
105
106    private byte [] concat(byte[] first, byte[] second) throws IOException {
107        ByteArrayOutputStream baos = new ByteArrayOutputStream();
108        baos.write(first);
109        baos.write(second);
110        byte [] result = baos.toByteArray();
111        baos.reset();
112        return result;
113    }
114
115    //https://stackoverflow.com/questions/2183240/java-integer-to-byte-array
116    public static final byte[] intToByteArray(int value) {
117        return new byte[] {
118                (byte)(value >>> 24),
119                (byte)(value >>> 16),
120                (byte)(value >>> 8),
121                (byte)value};
122    }
123}