LockTalk - Secure Chat Application

A multi-threaded chat application with JWT authentication, AES encryption, and MongoDB storage.

🔒 Security Features

1. JWT Authentication - Stateless tokens with HMAC256 signing, 24-hour expiration
2. Password Encryption - AES-encrypted passwords, never stored in plain text
3. AES Message Encryption - All messages encrypted with AES-256 before transmission
4. HMAC Message Integrity - Verifies messages haven't been tampered with
5. Secure MongoDB Connection - Encrypted connections, credentials in .env file
6. Thread-Safe Architecture - CopyOnWriteArrayList, separate thread per client

📋 Functionality

• User registration and login with JWT tokens
• Real-time encrypted messaging between multiple clients
• Message history sent to new clients when they join
• Automatic message broadcasting to all connected users
• Session persistence via JWT token file storage

🚀 Setup & Run

1. Configure .env File

Create .env in the ca1_group_k directory:

JWT_SECRET_KEY=your_secret_key_here
MONGODB_CONNECTION_STRING=mongodb+srv://username:password@cluster.mongodb.net/?appName=YourApp
MONGODB_DATABASE_NAME=YourDatabaseName
AES_SECRET_KEY=MTIzNDU2Nzg5MDEyMzQ1Ng==
HMAC_SECRET_KEY=your_super_secret_key_at_least_32_characters

2. Run Server

cd ca1_group_k
mvn compile exec:java -Dexec.mainClass="nci.security_fundamentals.server.ChatServer"

3. Run Client(s)

cd ca1_group_k
mvn compile exec:java -Dexec.mainClass="nci.security_fundamentals.client.Main"

Usage

1. Choose Register (1) or Login (2)
2. Enter credentials
3. Start sending encrypted messages

Prerequisites: Java 21+, Maven 3.6+, MongoDB Atlas account