Reduced ending timeout

src/main/java/Main/AES.java

@@ -0,0 +1,48 @@
+package Main;
+
+import javax.crypto.Cipher;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.IvParameterSpec;
+import java.security.SecureRandom;
+
+public class AES {
+
+    public static byte[] generateIv(){
+        SecureRandom randomSecureRandom = new SecureRandom();
+        byte[] iv = new byte[16];
+        randomSecureRandom.nextBytes(iv);
+        return iv;
+    }
+
+    public static byte[] encrypt(byte[] data, SecretKey secretKey, byte[] iv)
+    {
+        try
+        {
+            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
+            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
+            cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivParameterSpec);
+            return cipher.doFinal(data);
+        }
+        catch (Exception e)
+        {
+            System.out.println("Error while encrypting: " + e.toString());
+        }
+        return null;
+    }
+
+    public static byte[] decrypt(byte[] data, SecretKey secretKey, byte[] iv)
+    {
+        try
+        {
+            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
+            IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
+            cipher.init(Cipher.DECRYPT_MODE, secretKey, ivParameterSpec);
+            return cipher.doFinal(data);
+        }
+        catch (Exception e)
+        {
+            System.out.println("Error while decrypting: " + e.toString());
+        }
+        return null;
+    }
+}

src/main/java/Main/App.java

@@ -15,7 +15,7 @@ public class App {
             System.out.print("Enter server IP address (leave blank if hosting): ");
             String address = scanner.nextLine();
             Connection connection = new Connection(address);
-            Interactive interactive = new Interactive(connection.getIn(), connection.getOut());
+            DHInteractive interactive = new DHInteractive(connection.getIn(), connection.getOut());
             interactive.beginLoopAs(connection.isHost());
 
         } catch (IOException exception) {

src/main/java/Main/CommitmentInteractive.java

@@ -6,10 +6,10 @@ import java.io.Reader;
 import java.io.Writer;
 import java.util.Scanner;
 
-public class Interactive {
+public class CommitmentInteractive {
     ProtocolManager protocolManager;
 
-    public Interactive(Reader in, Writer out) {
+    public CommitmentInteractive(Reader in, Writer out) {
         this.protocolManager = new ProtocolManager(in, out);
     }
 

src/main/java/Main/Connection.java

@@ -4,13 +4,11 @@ import org.apache.log4j.Level;
 import org.apache.log4j.LogManager;
 import org.apache.log4j.Logger;
 
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStreamReader;
-import java.io.PrintWriter;
+import java.io.*;
 import java.net.ConnectException;
 import java.net.ServerSocket;
 import java.net.Socket;
+import java.nio.charset.StandardCharsets;
 
 public class Connection {
     private static final Logger logger = LogManager.getLogger(App.class);
@@ -46,8 +44,9 @@ public class Connection {
         } catch (ConnectException e) {
             makeServer();
         }
-        out = new PrintWriter(clientSocket.getOutputStream(), true);
-        in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+        out = new PrintWriter(new OutputStreamWriter(
+                clientSocket.getOutputStream(), StandardCharsets.UTF_16), true);
+        in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream(), "UTF-16"));
     }
 
     public PrintWriter getOut() {

src/main/java/Main/DHExchange.java

@@ -0,0 +1,108 @@
+package Main;
+
+import org.apache.log4j.Level;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
+
+import javax.crypto.KeyAgreement;
+import javax.crypto.interfaces.DHPublicKey;
+import javax.crypto.spec.DHParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+import java.security.*;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.X509EncodedKeySpec;
+
+public class DHExchange {
+    private static final Logger logger = LogManager.getLogger(App.class);
+    private KeyPair keyPair = null;
+    private KeyAgreement agreement = null;
+    private PublicKey thisPublicKey;
+    private PublicKey otherPublicKey;
+    private final int keySize;
+    private SecretKeySpec secretKey;
+
+
+    public DHExchange(int keySize, boolean isHost) {
+        this.keySize = keySize;
+        if (isHost)
+            createKeyPar();
+    }
+
+    void createKeyPar() {
+        logger.log(Level.INFO, "Generating " + keySize + "-bit key pair...");
+
+        try {
+            KeyPairGenerator kPairGen = KeyPairGenerator.getInstance("DH");
+            kPairGen.initialize(keySize);
+            keyPair = kPairGen.generateKeyPair();
+
+
+            agreement = KeyAgreement.getInstance("DH");
+            agreement.init(keyPair.getPrivate());
+        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
+            e.printStackTrace();
+        }
+        thisPublicKey = keyPair.getPublic();
+    }
+
+    void createKeyParFromPublicKey(byte[] publicKeyBytes) throws Exception {
+        if (keyPair != null)
+            throw new Exception("Key pair alredy exists! Perhaps is was generated before?");
+        try {
+            KeyFactory keyFactory = KeyFactory.getInstance("DH");
+            X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKeyBytes);
+
+            otherPublicKey = keyFactory.generatePublic(x509KeySpec);
+
+            DHParameterSpec dhParam = ((DHPublicKey) otherPublicKey).getParams();
+
+            logger.log(Level.INFO, "Generating " + keySize + "-bit key pair...");
+            KeyPairGenerator kPairGen = KeyPairGenerator.getInstance("DH");
+            kPairGen.initialize(dhParam);
+            keyPair = kPairGen.generateKeyPair();
+
+            agreement = KeyAgreement.getInstance("DH");
+            agreement.init(keyPair.getPrivate());
+
+            thisPublicKey = keyPair.getPublic();
+            agreement.doPhase(otherPublicKey, true);
+
+            generateSecret();
+
+        } catch (NoSuchAlgorithmException | InvalidKeySpecException | InvalidAlgorithmParameterException | InvalidKeyException e) {
+            e.printStackTrace();
+        }
+    }
+
+    void onRecievePubKey(byte[] publicKeyBytes) {
+        try {
+            KeyFactory keyFac = KeyFactory.getInstance("DH");
+
+            X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKeyBytes);
+            otherPublicKey = keyFac.generatePublic(x509KeySpec);
+            agreement.doPhase(otherPublicKey, true);
+
+            generateSecret();
+        } catch (NoSuchAlgorithmException | InvalidKeySpecException | InvalidKeyException e) {
+            e.printStackTrace();
+        }
+    }
+
+    byte[] getThisPublicKeyEncoded() {
+        return thisPublicKey.getEncoded();
+    }
+
+    byte[] getOtherPublicKeyEncoded() {
+        return otherPublicKey.getEncoded();
+    }
+
+    void generateSecret() {
+        byte[] secret = agreement.generateSecret();
+        secretKey = new SecretKeySpec(secret, 0, 16, "AES");
+    }
+
+    public SecretKeySpec getSecretKey() {
+        return secretKey;
+    }
+}
+

src/main/java/Main/DHInteractive.java

@@ -0,0 +1,150 @@
+package Main;
+
+import javax.crypto.SecretKey;
+import javax.crypto.spec.SecretKeySpec;
+import java.io.*;
+import java.nio.file.Files;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class DHInteractive {
+    ProtocolManager protocolManager;
+
+    public DHInteractive(Reader in, Writer out) {
+        this.protocolManager = new ProtocolManager(in, out);
+    }
+
+    void beginSenderInteractive(){
+        System.out.println("Starting DH key exchange...");
+        DHExchange dhExchange = new DHExchange(2048, true);
+        System.out.println("Your public key is: " + Utils.bytesToHex(dhExchange.getThisPublicKeyEncoded()));
+        System.out.println("Sending this public key to the other side...");
+        try {
+            protocolManager.sendMessage(dhExchange.getThisPublicKeyEncoded());
+            System.out.println("Key sent. Waiting for other sides public key...");
+
+            byte[] recvPKey = protocolManager.getMessageBytes();
+            System.out.println("Got key: " + Utils.bytesToHex(recvPKey));
+
+            System.out.println("Final agreement phase...");
+            dhExchange.onRecievePubKey(recvPKey);
+            SecretKeySpec secret = dhExchange.getSecretKey();
+            System.out.println("Secret is: " + Utils.bytesToHex(secret.getEncoded()));
+
+            System.out.println("Generating IV vector for AES ciphering...");
+
+            byte[] iv = AES.generateIv();
+
+            System.out.println("IV is: " + Utils.bytesToHex(iv));
+
+            // Sending IV as plaintext
+            protocolManager.sendMessage(iv);
+
+            System.out.println("Specify a file to send");
+            System.out.print("Path: ");
+
+            Scanner scanner = new Scanner(System.in);
+            String fPath = scanner.nextLine();
+
+            File file = new File(fPath);
+            long fSize = file.length();
+            System.out.printf("File: %s, size: %.4fkB\n", file.getName(), (double)fSize / 1000);
+            byte[] fBytes = Files.readAllBytes(file.toPath());
+
+            MessageDigest md5digest = MessageDigest.getInstance("MD5");
+            md5digest.update(fBytes);
+            byte[] checksum = md5digest.digest();
+            System.out.println("MD5 checksum: " + Utils.bytesToHex(checksum));
+
+            System.out.println("Encrypting...");
+
+            byte[] encryptedFile = AES.encrypt(fBytes, secret, iv);
+            byte[] encryptedFileName = AES.encrypt(file.getName().getBytes(), secret, iv);
+            System.out.println("Sending encrypted file...");
+            protocolManager.sendMessage(checksum);
+            protocolManager.sendMessage(encryptedFileName);
+            protocolManager.sendMessage(encryptedFile);
+
+            System.out.println("Done!");
+            try {
+                Thread.sleep(2000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+
+            System.out.println("File sent.");
+        } catch (IOException | NoSuchAlgorithmException exception) {
+            exception.printStackTrace();
+        }
+
+    }
+
+    void beginReceiverInteractive(){
+        System.out.println("Starting DH key exchange...");
+        DHExchange dhExchange = new DHExchange(2048, false);
+        try {
+            System.out.println("Waiting for other sides public key...");
+
+            byte[] recvPKey = protocolManager.getMessageBytes();
+            System.out.println("Got key: " + Utils.bytesToHex(recvPKey));
+            dhExchange.createKeyParFromPublicKey(recvPKey);
+
+            System.out.println("Your public key is: " + Utils.bytesToHex(dhExchange.getThisPublicKeyEncoded()));
+            System.out.println("Sending the key to the other side...");
+            protocolManager.sendMessage(dhExchange.getThisPublicKeyEncoded());
+
+            SecretKeySpec secret = dhExchange.getSecretKey();
+            System.out.println("Secret is: " + Utils.bytesToHex(secret.getEncoded()));
+
+            System.out.println("Waiting for IV...");
+            byte[] iv = protocolManager.getMessageBytes();
+            System.out.println("IV is: " + Utils.bytesToHex(iv));
+
+            System.out.println("Waiting for encrypted file...");
+
+            byte[] checksum = protocolManager.getMessageBytes();
+            byte[] encryptedFileName = protocolManager.getMessageBytes();
+            byte[] encryptedFile = protocolManager.getMessageBytes();
+
+            System.out.println("Decrypting...");
+            String decryptedFileName = new String(AES.decrypt(encryptedFileName, secret, iv));
+            byte[] decryptedFile = AES.decrypt(encryptedFile, secret, iv);
+
+            System.out.println("Filename: " + decryptedFileName);
+            File recievedFile = new File(decryptedFileName);
+            BufferedOutputStream stream = new BufferedOutputStream(new FileOutputStream(recievedFile));
+            stream.write(decryptedFile);
+            stream.flush();
+
+            System.out.println("File saved in " + recievedFile.getAbsolutePath());
+
+            System.out.println("Checking checksums...");
+            System.out.println("Expected: " + Utils.bytesToHex(checksum));
+
+            byte[] fBytes = Files.readAllBytes(recievedFile.toPath());
+
+            MessageDigest md5digest = MessageDigest.getInstance("MD5");
+            md5digest.update(fBytes);
+            byte[] recvChecksum = md5digest.digest();
+            System.out.println("MD5 checksum: " + Utils.bytesToHex(recvChecksum));
+
+            if(Arrays.equals(recvChecksum, checksum))
+                System.out.println("Checksum match positive.");
+            else
+                System.out.println("Checksum match negative! File damaged.");
+
+        } catch (Exception exception) {
+            exception.printStackTrace();
+        }
+    }
+
+    public void beginLoopAs(boolean isHost){
+        // Host (the one who starts the app first) is Alice - ciphers the message.
+        if(isHost)
+            beginSenderInteractive();
+        else
+            beginReceiverInteractive();
+    }
+}

src/main/java/Main/ProtocolMessage.java

@@ -52,12 +52,12 @@ public class ProtocolMessage {
 
     private void composeRawData(int length, char[] message){
         this.raw = new char[4 + length];
-        byte[] integer = intToByte(length);
+        char[] integer = intToCharArray(length);
 
-        this.raw[0] = (char)integer[0];
-        this.raw[1] = (char)integer[1];
-        this.raw[2] = (char)integer[2];
-        this.raw[3] = (char)integer[3];
+        this.raw[0] = integer[0];
+        this.raw[1] = integer[1];
+        this.raw[2] = integer[2];
+        this.raw[3] = integer[3];
 
         System.arraycopy(message, 0, this.raw, 4, message.length);
     }
@@ -106,10 +106,10 @@ public class ProtocolMessage {
 
     public void readFromStream(Reader reader) throws IOException {
         int totalBytesRead = 0;
-        char[] buffer = new char[2048];
+        char[] lenBuffer = new char[4];
         // Read first 4 bytes containing the length of the incoming message
         while(totalBytesRead != 4){
-            int bytesRead = reader.read(buffer, totalBytesRead, 4 - totalBytesRead);
+            int bytesRead = reader.read(lenBuffer, totalBytesRead, 4 - totalBytesRead);
             if (bytesRead == -1) {
                 logger.log(Level.ERROR, "Invalid packet.");
                 return;
@@ -117,7 +117,10 @@ public class ProtocolMessage {
                 totalBytesRead += bytesRead;
         }
 
-        int messageLength = charArrayToInt(buffer);
+        int messageLength = charArrayToInt(lenBuffer);
+
+        char[] buffer = new char[4 + messageLength];
+        System.arraycopy(lenBuffer, 0, buffer, 0, totalBytesRead);
         while(totalBytesRead != 4 + messageLength){
             int bytesRead = reader.read(buffer, totalBytesRead, messageLength - totalBytesRead + 4);
             if (bytesRead == -1) {

src/test/java/Main/AESTest.java

@@ -0,0 +1,36 @@
+package Main;
+
+import org.junit.jupiter.api.Test;
+
+import javax.crypto.Cipher;
+import javax.crypto.KeyGenerator;
+import javax.crypto.NoSuchPaddingException;
+import javax.crypto.SecretKey;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class AESTest {
+    @Test
+    void AESBothSidesTest(){
+        Cipher cipher = null;
+        try {
+            cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
+
+            KeyGenerator keyGen = KeyGenerator.getInstance("AES");
+            keyGen.init(256); // for example
+            SecretKey secretKey = keyGen.generateKey();
+            byte[] iv = new byte[cipher.getBlockSize()];
+            SecureRandom randomSecureRandom = new SecureRandom();
+            randomSecureRandom.nextBytes(iv);
+            byte[] data = Utils.stringToBytes("ASDASDASDASD12esadasd ");
+            byte[] encoded = AES.encrypt(data, secretKey, iv);
+            byte[] decoded = AES.decrypt(encoded, secretKey, iv);
+            assertArrayEquals(data, decoded);
+        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
+            e.printStackTrace();
+        }
+    }
+}

src/test/java/Main/DHExchangeTest.java

@@ -0,0 +1,22 @@
+package Main;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class DHExchangeTest {
+
+    @Test
+    void KeyMatchAfterExchangeTest(){
+        DHExchange alice = new DHExchange(2048, true);
+        DHExchange bob = new DHExchange(2048, false);
+        try {
+            bob.createKeyParFromPublicKey(alice.getThisPublicKeyEncoded());
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+        alice.onRecievePubKey(bob.getThisPublicKeyEncoded());
+
+        assertEquals(bob.getSecretKey(), alice.getSecretKey());
+    }
+}