Peer-to-Peer-Chat/src/main/java/storage/SecureStorage.java

package storage;

import model.Chat;
import java.io.*;
import java.nio.file.*;
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;
import java.util.*;

public class SecureStorage {
    public static void saveChats(List<Chat> chats, String password) throws Exception {
        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        ObjectOutputStream objOut = new ObjectOutputStream(byteStream);
        objOut.writeObject(chats);
        objOut.close();

        byte[] data = byteStream.toByteArray();
        byte[] key = Arrays.copyOf(password.getBytes(), 16); // AES 128-bit
        SecretKeySpec secretKey = new SecretKeySpec(key, "AES");

        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
        byte[] encrypted = cipher.doFinal(data);

        Files.write(Paths.get("chats.dat"), encrypted);
    }
}