CipherLink – Secure Multi-Client Communication Framework with End-to-End Encryption

📌 Overview

CipherLink is a secure real-time multi-client chat application developed using Python Socket Programming and Tkinter GUI. The application enables multiple users to communicate securely over local networks or the internet using End-to-End Encryption (E2EE).

The project demonstrates:

• Socket Programming
• Client-Server Architecture
• Multithreading
• GUI Development using Tkinter
• End-to-End Encryption using Fernet
• Internet Deployment using Ngrok
• Online Users Synchronization
• Chat Log Management

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✨ Features

• 🔒 End-to-End Encrypted Messaging
• 🌐 Internet-based Communication using Ngrok
• 👥 Multi-Client Communication
• 📋 Dynamic Online Users List
• 💬 Real-Time Messaging
• 🖥️ Tkinter GUI Interface
• 🧵 Multi-threaded Server Handling
• 📝 Local Chat Log Saving
• ⚡ Lightweight and Fast
• 🔐 Password-based Encryption using Fernet

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🛠️ Technologies Used

Technology	Purpose
Python 3.x	Core Programming
Socket Programming	Networking Communication
Tkinter	GUI Development
Threading	Multi-client Handling
Cryptography (Fernet)	End-to-End Encryption
Ngrok	Internet Deployment
PyInstaller	EXE File Generation

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🏗️ Project Architecture

               ┌─────────────────┐
               │     SERVER      │
               │  (Central Hub)  │
               └────────┬────────┘
                        │
        ┌───────────────┼───────────────┐
        │               │               │
 ┌────────────┐ ┌────────────┐ ┌────────────┐
 │  CLIENT 1  │ │  CLIENT 2  │ │  CLIENT N  │
 │    GUI     │ │    GUI     │ │    GUI     │
 └────────────┘ └────────────┘ └────────────┘

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🔐 Encryption Workflow

1. User enters a shared password.
2. Password is converted into a secure encryption key using PBKDF2HMAC.
3. Messages are encrypted using Fernet encryption before transmission.
4. Server only forwards encrypted packets.
5. Receiving client decrypts the message locally.

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📂 Project Structure

CipherLink/
│
├── modified_server.py
├── modified_client.py
├── chat_logs/
├── README.md
└── requirements.txt

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⚙️ Installation Guide

Step 1 — Install Python

Download and install Python 3.8+:

https://www.python.org/downloads/

During installation:

• Enable “Add Python to PATH”

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📦 Step 2 — Install Required Libraries

Open terminal inside project directory:

pip install cryptography

Optional (for EXE conversion):

pip install pyinstaller

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🚀 Running the Project

🖥️ Server Setup

Open terminal inside project directory:

python modified_server.py

Expected Output:

Starting secure chat server on 0.0.0.0:5000

Keep this terminal OPEN.

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🌐 Internet Deployment using Ngrok

Step 1 — Download Ngrok

https://ngrok.com/download

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Step 2 — Add Auth Token

After signup:

ngrok config add-authtoken YOUR_AUTH_TOKEN

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Step 3 — Start TCP Tunnel

Open another terminal:

ngrok tcp 5000

Example Output:

Forwarding tcp://0.tcp.in.ngrok.io:19345 -> localhost:5000

Keep this terminal OPEN.

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💻 Client Configuration

Open:

modified_client.py

Update these lines:

SERVER_HOST = "0.tcp.in.ngrok.io"
SERVER_PORT = 19345

Replace with your own ngrok host and port.

Save the file.

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▶️ Running Client

python modified_client.py

Steps:

1. Enter username
2. Enable encryption
3. Enter shared password
4. Click “Set Password”
5. Click “Connect”

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👥 Connecting Friend Across Internet

Send your friend:

• modified_client.py

OR preferably:

• modified_client.exe

Your friend should:

1. Run client
2. Enter username
3. Enter same password
4. Click Connect

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🧊 Convert Client to EXE

Install requirements:

pip install pyinstaller cryptography

Generate EXE:

pyinstaller --onefile --windowed modified_client.py

Generated EXE location:

dist/modified_client.exe

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📋 Chat Logs

All messages are automatically stored locally inside:

chat_logs/

Logs include:

• Username
• Timestamp
• Messages

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📸 Recommended Screenshots

• Server running terminal
• Ngrok tunnel
• Client GUI
• Multi-client communication
• Encrypted communication
• Online users list
• Wrong password handling
• Chat log generation

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🔮 Future Enhancements

• File Sharing
• Private Messaging
• Group Chat Rooms
• Database Integration
• Cloud Deployment
• Mobile Application
• Voice & Video Calling
• TLS Secured Connections

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🎯 Applications

• Secure Internal Communication
• Educational Networking Projects
• Cybersecurity Demonstrations
• Real-Time Messaging Systems
• Lightweight Communication Platforms

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👨‍💻 Author

Anmol B.E. Computer Science & Engineering Chandigarh College of Engineering & Technology (Degree Wing)

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📄 License

This project is developed for academic and educational purposes.