PmDHAXmE

1import java.net.*;
2import java.io.*;
3import javax.crypto.*;
4import javax.crypto.spec.IvParameterSpec;
5import javax.crypto.spec.SecretKeySpec;
6import java.security.*;
7
8public class Client {
9    public static void main(String args[]) {
10
11        Socket s = null;
12        int serversocket = 4567;
13        try {
14            s = new Socket("127.0.0.1", serversocket);
15
16            DataInputStream in = new DataInputStream(s.getInputStream());
17            DataOutputStream out = new DataOutputStream(s.getOutputStream());
18
19            while (true){
20                //key
21                byte [] key = {1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4};
22
23                //hash function and new keys
24                MessageDigest md = MessageDigest.getInstance("SHA-256");
25
26                byte [] byte1 = {1};
27                byte [] aux1 = concat(key, byte1);
28                byte [] hash1= md.digest(aux1);
29                SecretKey k1 = new SecretKeySpec(hash1, 0, hash1.length, "AES");
30
31                byte [] byte2 = {2};
32                byte [] aux2 = concat(key, byte2);
33                byte [] hash2= md.digest(aux2);
34                SecretKey k2 = new SecretKeySpec(hash2, 0, hash2.length, "HMAC");
35
36                //message authentication code
37                Mac mac = Mac.getInstance("HmacSHA256");
38                mac.init(k2);
39                int nSeq = 0;
40
41                //nonce - sends the bytes in plaintext so that the server can create the same IV
42                byte[] bytesForIV=new byte[16];
43                SecureRandom sr = new SecureRandom();
44                sr.nextBytes(bytesForIV);
45                IvParameterSpec iv = new IvParameterSpec(bytesForIV);
46                out.write(bytesForIV);
47
48                //E(m, k1) = c
49                Cipher c = Cipher.getInstance("AES/CTR/PKCS5Padding");
50                c.init(Cipher.ENCRYPT_MODE, k1, iv);
51                String text = "";
52                InputStreamReader input = new InputStreamReader(System.in);
53                BufferedReader reader = new BufferedReader(input);
54                while (true) {
55                    try {
56                        text = reader.readLine();
57                    }
58                    catch (Exception e) {}
59
60                    byte [] enc = c.doFinal(text.getBytes());
61                    byte [] nSeqByte = intToByteArray(nSeq);
62                    byte [] authTagAux = concat(enc, nSeqByte);
63                    byte [] authTag = mac.doFinal(authTagAux);
64                    out.write(authTag);
65                    out.write("\n".getBytes());
66                    out.write(enc);
67                    nSeq++;
68                }
69            }
70        } catch (UnknownHostException e) {
71            System.out.println("Sock:" + e.getMessage());
72        } catch (EOFException e) {
73            System.out.println("EOF:" + e.getMessage());
74        } catch (IOException e) {
75            System.out.println("IO:" + e.getMessage());
76        } catch (NoSuchPaddingException e) {
77            e.printStackTrace();
78        } catch (NoSuchAlgorithmException e) {
79            e.printStackTrace();
80        } catch (InvalidAlgorithmParameterException e) {
81            e.printStackTrace();
82        } catch (InvalidKeyException e) {
83            e.printStackTrace();
84        } catch (BadPaddingException e) {
85            e.printStackTrace();
86        } catch (IllegalBlockSizeException e) {
87            e.printStackTrace();
88        } finally {
89            if (s != null)
90                try {
91                    s.close();
92                } catch (IOException e) {
93                    System.out.println("close:" + e.getMessage());
94                }
95        }
96    }
97
98    private static byte [] concat(byte[] first, byte[] second) throws IOException {
99        ByteArrayOutputStream baos = new ByteArrayOutputStream();
100        baos.write(first);
101        baos.write(second);
102        byte [] result = baos.toByteArray();
103        baos.reset();
104        return result;
105    }
106
107    //https://stackoverflow.com/questions/2183240/java-integer-to-byte-array
108    public static final byte[] intToByteArray(int value) {
109        return new byte[]{
110                (byte)(value >>> 24),
111                (byte)(value >>> 16),
112                (byte)(value >>> 8),
113                (byte)value};
114    }
115}