Exemplo n.º 1
0
  /**
   * Sends the specified file to the client. File must exist or client and server threads will hang
   * indefinitely. Generates a session key to encrypt the file over transfer; session key is
   * encrypted using the client's public (asymmetric) key.
   *
   * @param aFile The name or path of the file to send.
   * @throws IOException Error reading from socket.
   */
  private void sendFile(String aFile) throws IOException {
    try {
      // get client public key
      ObjectInputStream clientPubIn = new ObjectInputStream(connectedSocket.getInputStream());
      PublicKey clientPublicKey = (PublicKey) clientPubIn.readObject();

      // generate key string and send to client using their public key encrypted with RSA
      // (asymmetric)
      String keyString = generateKeyString();
      Cipher keyCipher = Cipher.getInstance("RSA");
      keyCipher.init(Cipher.ENCRYPT_MODE, clientPublicKey);
      SealedObject sealedKeyString = new SealedObject(keyString, keyCipher);
      ObjectOutputStream testOut = new ObjectOutputStream(outToClient);
      testOut.writeObject(sealedKeyString);
      testOut.flush();

      // generate key spec from keyString
      SecretKeySpec keySpec = new SecretKeySpec(keyString.getBytes(), "DES");

      // set up encryption
      Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
      cipher.init(Cipher.ENCRYPT_MODE, keySpec);
      CipherOutputStream cipherOut = new CipherOutputStream(outToClient, cipher);

      // send file
      byte[] fileBuffer = new byte[BUFFER_SIZE];
      InputStream fileReader = new BufferedInputStream(new FileInputStream(aFile));
      int bytesRead;
      while ((bytesRead = fileReader.read(fileBuffer)) != EOF) {
        cipherOut.write(fileBuffer, 0, bytesRead);
      }
      cipherOut.flush();
      cipherOut.close();
      disconnect();
    } catch (NoSuchPaddingException nspe) {
      System.out.println("No such padding.");
    } catch (NoSuchAlgorithmException nsae) {
      System.out.println("Invalid algorithm entered");
    } catch (ClassNotFoundException cnfe) {
      System.out.println("Class not found.");
    } catch (InvalidKeyException ike) {
      System.out.println("Invalid key used for file encryption.");
    } catch (FileNotFoundException fnfe) {
      System.out.println("Invalid file entered.");
      return;
    } catch (IllegalBlockSizeException ibse) {
      System.out.println("Illegal block size used for encryption.");
    }
  }
Exemplo n.º 2
0
  /**
   * @param s
   * @return
   * @throws GeneralSecurityException
   * @throws UnsupportedEncodingException
   */
  public static String decrypt(final String s)
      throws GeneralSecurityException, UnsupportedEncodingException {
    String decrypted = null;

    try {
      if (s != null) {
        final SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        final SecretKey secretKey =
            secretKeyFactory.generateSecret(new PBEKeySpec(secret.toCharArray()));
        final Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
        cipher.init(Cipher.DECRYPT_MODE, secretKey, new PBEParameterSpec(SALT, 20));
        final byte[] stringBytes = s.getBytes("UTF-8");
        final byte[] decodedBytes = Base64.decode(stringBytes, Base64.DEFAULT);
        final byte[] decryptedBytes = cipher.doFinal(decodedBytes);
        decrypted = new String(decryptedBytes, "UTF-8");
      }
    } catch (GeneralSecurityException x) {
      throw x;
    } catch (UnsupportedEncodingException x) {
      throw x;
    } catch (Exception x) {
      DBG.m(x);
    }

    return decrypted;
  }
Exemplo n.º 3
0
  public void run() {
    try {
      ObjectInputStream ois = new ObjectInputStream(s.getInputStream());
      ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());

      BigInteger bg = dhSpec.getG();
      BigInteger bp = dhSpec.getP();
      oos.writeObject(bg);
      oos.writeObject(bp);

      KeyPairGenerator kpg = KeyPairGenerator.getInstance("DH");
      kpg.initialize(1024);
      KeyPair kpa = (KeyPair) ois.readObject();
      KeyAgreement dh = KeyAgreement.getInstance("DH");
      KeyPair kp = kpg.generateKeyPair();

      oos.writeObject(kp);

      dh.init(kp.getPrivate());
      Key pk = dh.doPhase(kpa.getPublic(), true);

      MessageDigest sha256 = MessageDigest.getInstance("SHA-256");
      byte[] rawbits = sha256.digest(dh.generateSecret());

      Cipher c = Cipher.getInstance(CIPHER_MODE);
      SecretKey key = new SecretKeySpec(rawbits, 0, 16, "AES");
      byte ivbits[] = (byte[]) ois.readObject();
      IvParameterSpec iv = new IvParameterSpec(ivbits);
      c.init(Cipher.DECRYPT_MODE, key, iv);

      Mac m = Mac.getInstance("HmacSHA1");
      SecretKey mackey = new SecretKeySpec(rawbits, 16, 16, "HmacSHA1");
      m.init(mackey);

      byte ciphertext[], cleartext[], mac[];
      try {
        while (true) {
          ciphertext = (byte[]) ois.readObject();
          mac = (byte[]) ois.readObject();
          if (Arrays.equals(mac, m.doFinal(ciphertext))) {
            cleartext = c.update(ciphertext);
            System.out.println(ct + " : " + new String(cleartext, "UTF-8"));
          } else {
            // System.exit(1);
            System.out.println(ct + "error");
          }
        }
      } catch (EOFException e) {
        cleartext = c.doFinal();
        System.out.println(ct + " : " + new String(cleartext, "UTF-8"));
        System.out.println("[" + ct + "]");
      } finally {
        if (ois != null) ois.close();
        if (oos != null) oos.close();
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
  public static void main(String[] args) throws Exception {
    // prompt user to enter a port number

    System.out.print("Enter the port number: ");
    Scanner scan = new Scanner(System.in);
    int port = scan.nextInt();
    scan.nextLine();
    System.out.print("Enter the host name: ");
    String hostName = scan.nextLine();

    // Initialize a key pair generator with the SKIP parameters we sepcified, and genrating a pair
    // This will take a while: 5...15 seconrds

    System.out.println("Generating a Diffie-Hellman keypair: ");
    KeyPairGenerator kpg = KeyPairGenerator.getInstance("DH");
    kpg.initialize(PARAMETER_SPEC);
    KeyPair keyPair = kpg.genKeyPair();
    System.out.println("key pair has been made...");

    // one the key pair has been generated, we want to listen on
    // a given port for a connection to come in
    // once we get a connection, we will get two streams, One for input
    // and one for output
    // open a port and wait for a connection

    ServerSocket ss = new ServerSocket(port);
    System.out.println("Listeining on port " + port + " ...");
    Socket socket = ss.accept();

    // use to output and input primitive data type

    DataOutputStream out = new DataOutputStream(socket.getOutputStream());

    // next thing to do is send our public key and receive client's
    // this corresponds to server step 3 and step 4 in the diagram

    System.out.println("Sending my public key...");
    byte[] keyBytes = keyPair.getPublic().getEncoded();
    out.writeInt(keyBytes.length);
    out.write(keyBytes);
    System.out.println("Server public key bytes: " + CryptoUtils.toHex(keyBytes));

    // receive the client's public key

    System.out.println("Receiving client's public key...");
    DataInputStream in = new DataInputStream(socket.getInputStream());
    keyBytes = new byte[in.readInt()];
    in.readFully(keyBytes);

    // create client's public key

    KeyFactory kf = KeyFactory.getInstance("DH");
    X509EncodedKeySpec x509Spec = new X509EncodedKeySpec(keyBytes);
    PublicKey clientPublicKey = kf.generatePublic(x509Spec);

    // print out client's public key bytes

    System.out.println(
        "Client public key bytes: " + CryptoUtils.toHex(clientPublicKey.getEncoded()));

    // we can now use the client's public key and
    // our own private key to perform the key agreement

    System.out.println("Performing the key agreement ... ");
    KeyAgreement ka = KeyAgreement.getInstance("DH");
    ka.init(keyPair.getPrivate());
    ka.doPhase(clientPublicKey, true);

    // in a chat application, each character is sendt over the wire, separetly encrypted,
    // Instead of using ECB, we are goin to use CFB, with a block size of 8 bits(1byte)
    // to send each character. We will encrypt the same character in a different way
    // each time. But in order to use CFB8, we need an IVof 8 bytes. We will create
    // that IV randomly and and send it to the client. It doesn't matter if somoene
    // eavesdrops on the IV when it is sent over the wire. it's not sensitive info

    // creating the IV and sending it corresponds to step 6 and 7

    byte[] iv = new byte[8];
    SecureRandom sr = new SecureRandom();
    sr.nextBytes(iv);
    out.write(iv);

    // we generate the secret byte array we share with the client and use it
    // to create the session key (Step 8)

    byte[] sessionKeyBytes = ka.generateSecret();

    // create the session key

    SecretKeyFactory skf = SecretKeyFactory.getInstance("DESede");
    DESedeKeySpec DESedeSpec = new DESedeKeySpec(sessionKeyBytes);
    SecretKey sessionKey = skf.generateSecret(DESedeSpec);

    // printout session key bytes

    System.out.println("Session key bytes: " + CryptoUtils.toHex(sessionKey.getEncoded()));

    // now use tha that session key and IV to create a CipherInputStream. We will use them to read
    // all character
    // that are sent to us by the client

    System.out.println("Creating the cipher stream ...");
    Cipher decrypter = Cipher.getInstance("DESede/CFB8/NoPadding");
    IvParameterSpec spec = new IvParameterSpec(iv);
    decrypter.init(Cipher.DECRYPT_MODE, sessionKey, spec);
    CipherInputStream cipherIn = new CipherInputStream(socket.getInputStream(), decrypter);

    // we just keep reading the input and print int to the screen, until -1 sent over

    int theCharacter = 0;
    theCharacter = cipherIn.read();
    while (theCharacter != -1) {
      System.out.print((char) theCharacter);
      theCharacter = cipherIn.read();
    }
    // once -1 is received we want to close up our stream and exit

    cipherIn.close();
    in.close();
    out.close();
    socket.close();
  }