💬 ChatNet

Secure Peer-to-Peer Chat Application with Advanced Encryption

Features • Architecture • Installation • Usage • Security

📖 Introduction

ChatNet is a modern, cross-platform peer-to-peer chat application built with React Native. It enables secure, real-time communication over local networks (LAN/WiFi) with enterprise-grade encryption and authentication mechanisms.

Unlike traditional chat applications that rely on centralized servers, ChatNet establishes direct TCP connections between devices, ensuring privacy, low latency, and complete control over your data.

Why ChatNet?

🔒 Privacy-First: No servers, no data collection, no third parties
🚀 Real-Time: Direct P2P connections with minimal latency
🛡️ Military-Grade Encryption: Multiple encryption algorithms (AES-256, RSA, DES, etc.)
🔐 Cryptographic Authentication: ECDSA digital signatures prevent message tampering
📱 Cross-Platform: Works on Android and iOS
🎨 Rich Media: Send text, images, and voice messages
🔑 Secure Key Exchange: Automated Diffie-Hellman key negotiation

✨ Key Features

🔐 Multiple Encryption Modes

Algorithm	Type	Key Size	Use Case
AES-256	Symmetric	256-bit	Production-ready, high security
RSA Hybrid	Asymmetric + Symmetric	2048-bit RSA + 256-bit AES	Maximum security with perfect forward secrecy
Triple DES	Symmetric	168-bit	Legacy compatibility
Playfair	Classical	Variable	Educational purposes
Caesar	Classical	1-25 shift	Educational purposes

🛡️ Advanced Security Features

ECDSA Digital Signatures: Verify message authenticity and integrity
ECDH Key Exchange: Secure automated key negotiation over insecure channels
Perfect Forward Secrecy: Each message uses a unique encryption key (RSA mode)
Anti-Tampering: Automatic detection of modified messages

📱 Rich Communication

💬 Text Messaging: Encrypted real-time chat
🖼️ Image Sharing: Send photos with automatic compression
🎤 Voice Messages: Record and send audio clips
⏱️ Timestamps: Track message history
📊 Delivery Status: Real-time connection monitoring

🏗️ Architecture Overview

System Architecture

Message Flow (Full Security Mode)

Technology Stack

📋 Prerequisites

Development Environment

Requirement	Version	Purpose
Node.js	≥ 20.x	JavaScript runtime
npm or yarn	Latest	Package manager
Git	Latest	Version control

Android Development

Tool	Version	Notes
Android Studio	Godzilla (2024)+	IDE
JDK	17 or 21	Java Development Kit
Android SDK	API 35	Build Tools 35.0.0
Gradle	8.10.2	Build system
Android Gradle Plugin	8.7.3	Build plugin

Minimum Device Requirements:

Android 5.0+ (API 21+)
100MB free storage
WiFi or LAN connectivity

iOS Development (macOS only)

Tool	Version	Notes
macOS	Ventura (13.0)+	Operating system
Xcode	14.0+	IDE
CocoaPods	Latest	Dependency manager
iOS Deployment Target	13.4+	Minimum iOS version

🚀 Installation

1. Clone the Repository

git clone https://github.com/nnkhanhduy/ChatNet.git
cd ChatNet

2. Install Dependencies

# Using npm
npm install

# Or using yarn
yarn install

3. iOS Setup (macOS only)

cd ios
pod install
cd ..

4. Android Configuration

Ensure android/local.properties exists with your SDK path:

sdk.dir=C:\\Users\\YourUsername\\AppData\\Local\\Android\\sdk

Note: Replace YourUsername with your actual Windows username.

📱 Running the Application

Start Metro Bundler

In your terminal, start the Metro development server:

npm start

# Or with network access for physical devices
npm run start:network

Keep this terminal running throughout development.

Run on Android

Open a new terminal and execute:

# Run on connected device or emulator
npm run android

# Or using React Native CLI
npx react-native run-android

Troubleshooting:

Enable USB Debugging on your Android device
Check connected devices: adb devices
For multiple devices: adb -s <device_id> install app.apk

Run on iOS (macOS only)

# Default simulator
npm run ios

# Specific simulator
npx react-native run-ios --simulator="iPhone 15 Pro"

# Physical device (requires Apple Developer Account)
npx react-native run-ios --device

📦 Building for Production

Android APK

Debug Build

# Using npm script
npm run build:apk

# Or manually
cd android
./gradlew assembleDebug
cd ..

# Output: android/app/build/outputs/apk/debug/app-debug.apk

Release Build (Signed)

npm run build:release

# Output: android/app/build/outputs/apk/release/app-release.apk

Configure Signing in android/app/build.gradle:

signingConfigs {
    release {
        storeFile file('my-release-key.keystore')
        storePassword 'your-store-password'
        keyAlias 'my-key-alias'
        keyPassword 'your-key-password'
    }
}

Install APK on Device

# Debug APK
npm run install:apk

# Release APK
npm run install:release

# Manual installation
adb install -r path/to/app.apk

💡 Usage

Initial Setup

Launch the app on both devices
Ensure both devices are on the same WiFi/LAN network
Tap the ⚙️ Settings icon in the top-right corner

Configuration

Device A:

Note your IP address (e.g., 192.168.1.100)
Enter Device B's IP in "🌐 Recipient IP"
Choose encryption mode (recommended: AES or RSA)
Set encryption key (for AES/DES) or exchange RSA keys

Device B:

Note your IP address (e.g., 192.168.1.101)
Enter Device A's IP in "🌐 Recipient IP"
Use the same encryption settings as Device A

Encryption Modes Setup

AES/DES Mode (Shared Key)

Device A: Key = "my_secret_key_123"
Device B: Key = "my_secret_key_123" (must match)

RSA Hybrid Mode (Public Key Exchange)

Device A:
1. Tap "Generate RSA Keys"
2. Copy your public key
3. Share with Device B (via QR code, text, etc.)
4. Paste Device B's public key in settings

Device B:
1. Tap "Generate RSA Keys"
2. Copy your public key
3. Share with Device A
4. Paste Device A's public key in settings

ECDH Key Exchange (Automated)

Device A:
1. Tap "Generate ECDH Keys"
2. Tap "Start Key Exchange"
3. Wait for Device B to respond

Device B:
1. Tap "Generate ECDH Keys"
2. Receive key exchange request
3. Shared key automatically configured ✓

Sending Messages

Text: Type in the input field and tap send ✉️
Images: Tap 📷 icon and select from gallery
Voice: Tap and hold 🎤 to record, release to send

Example Scenario

Device A (192.168.1.100):
├─ Recipient IP: 192.168.1.101
├─ Encryption: AES
├─ Key: "secure_key_2024"
└─ Message: "Hello, World!"
    └─ Encrypted: "U2FsdGVkX1+..."
        └─ Sent via TCP

Device B (192.168.1.101):
├─ Recipient IP: 192.168.1.100
├─ Encryption: AES
├─ Key: "secure_key_2024" (matches Device A)
└─ Received: "U2FsdGVkX1+..."
    └─ Decrypted: "Hello, World!" ✓

🔒 Security Features

ChatNet implements multiple layers of security. For detailed cryptographic specifications, see SECURITY.md.

Encryption Algorithms

1. AES-256 (Recommended)

Type: Symmetric block cipher
Key Size: 256 bits
Mode: CBC with PKCS7 padding
Use Case: Production environments

2. RSA Hybrid Encryption

Type: Asymmetric + Symmetric
RSA Key Size: 2048 bits
AES Key Size: 256 bits
Features: Perfect forward secrecy, unlimited message length
Use Case: Maximum security requirements

3. Triple DES

Type: Symmetric block cipher
Key Size: 168 bits (3 × 56-bit keys)
Mode: CBC
Use Case: Legacy system compatibility

4. Playfair Cipher

Type: Classical digraph substitution
Use Case: Educational purposes

5. Caesar Cipher

Type: Classical substitution
Shift: 1-25 positions
Use Case: Educational purposes

Authentication & Key Exchange

ECDSA Digital Signatures

Curve: secp256k1 (Bitcoin curve)
Hash: SHA-256
Purpose: Message authentication and integrity verification

ECDH Key Exchange

Curve: secp256k1
Purpose: Secure shared secret generation
Feature: Automated key negotiation

Security Best Practices

Important

Always use AES-256 or RSA Hybrid for production
Enable Digital Signatures to prevent message tampering
Use ECDH Key Exchange instead of manual key sharing
Never share private keys or encryption keys over insecure channels
Regularly regenerate RSA key pairs

Warning

Caesar and Playfair ciphers are NOT secure for real-world use. They are included for educational purposes only.

📁 Project Structure

ChatNet/
├── android/                    # Android native code
│   ├── app/
│   │   ├── build.gradle       # App-level Gradle config
│   │   └── src/               # Android source files
│   └── build.gradle           # Project-level Gradle config
│
├── ios/                        # iOS native code
│   ├── ChatNET/               # iOS app files
│   ├── ChatNET.xcodeproj/     # Xcode project
│   └── Podfile                # CocoaPods dependencies
│
├── src/                        # Application source code
│   ├── components/            # React components
│   │   ├── ChatInput.tsx      # Message input component
│   │   ├── ChatMessage.tsx    # Message display component
│   │   ├── Header.tsx         # App header
│   │   └── SettingsModal.tsx  # Settings & configuration
│   │
│   ├── hooks/                 # Custom React hooks
│   │   └── useTcpSocket.ts    # TCP socket management
│   │
│   ├── utils/                 # Utility functions
│   │   ├── aesCipher.ts       # AES-256 encryption
│   │   ├── caesarCipher.ts    # Caesar cipher
│   │   ├── desCipher.ts       # Triple DES encryption
│   │   ├── playfairCipher.ts  # Playfair cipher
│   │   ├── rsaCipher.ts       # RSA hybrid encryption
│   │   ├── security.ts        # ECDSA & ECDH implementation
│   │   ├── cryptoPolyfill.ts  # Crypto polyfills
│   │   └── responsive.ts      # Responsive scaling utilities
│   │
│   ├── types.ts               # TypeScript type definitions
│   └── constants.ts           # App constants
│
├── assets/                     # Static assets
│   └── Logo.jpg               # App logo
│
├── App.tsx                     # Root component
├── index.js                    # App entry point
├── package.json                # Dependencies & scripts
├── tsconfig.json               # TypeScript configuration
├── babel.config.js             # Babel configuration
├── metro.config.js             # Metro bundler config
├── README.md                   # This file
└── SECURITY.md                 # Security documentation

🤝 Contributing

We welcome contributions from the community! Here's how you can help:

Reporting Bugs

Check if the issue already exists in Issues
Create a new issue with:
- Clear title and description
- Steps to reproduce
- Expected vs actual behavior
- Screenshots (if applicable)
- Device info (OS, version, etc.)

Suggesting Features

Open an issue with the enhancement label
Describe the feature and its use case
Explain why it would benefit users

Pull Requests

Fork the repository
Create a feature branch: git checkout -b feature/amazing-feature
Make your changes
Test thoroughly on both Android and iOS
Commit with clear messages: git commit -m 'Add amazing feature'
Push to your fork: git push origin feature/amazing-feature
Open a Pull Request

Development Guidelines

Follow existing code style (TypeScript, ESLint)
Add comments for complex logic
Update documentation for new features
Ensure backward compatibility
Test on multiple devices

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

MIT License

Copyright (c) 2024 ChatNet Contributors

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

🙏 Acknowledgments

ChatNet is built with amazing open-source technologies:

React Native - Cross-platform mobile framework
crypto-js - Cryptographic algorithms
elliptic - Elliptic curve cryptography
jsrsasign - RSA cryptography
react-native-tcp-socket - TCP networking

Special thanks to all contributors and the open-source community.

⭐ If you find ChatNet useful, please star this repository! ⭐

⬆ Back to Top

Name		Name	Last commit message	Last commit date
Latest commit History 8 Commits
.bundle		.bundle
__tests__		__tests__
android		android
assets		assets
diagrams		diagrams
ios		ios
src		src
.eslintrc.js		.eslintrc.js
.gitignore		.gitignore
.prettierrc.js		.prettierrc.js
.watchmanconfig		.watchmanconfig
App.tsx		App.tsx
Gemfile		Gemfile
README.md		README.md
SECURITY.md		SECURITY.md
app.json		app.json
babel.config.js		babel.config.js
generate-diagrams.bat		generate-diagrams.bat
generate-diagrams.sh		generate-diagrams.sh
index.js		index.js
jest.config.js		jest.config.js
metro.config.js		metro.config.js
package-lock.json		package-lock.json
package.json		package.json
tsconfig.json		tsconfig.json

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