MyChain – Custom Cryptocurrency Blockchain Project

This project was built as a final assignment for the course Krypto Valuta och Nätverk, implementing a complete blockchain system with user authentication, mining, transaction validation, node synchronization, and a modern web interface.

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Features

• Custom blockchain with genesis block, mining, and reward system.
• User registration & login using JWT.
• Transaction handling with balance validation and reward logic.
• Mining functionality that creates blocks and distributes rewards.
• Peer-to-peer synchronization between multiple nodes (WebSocket + HTTP).
• TDD (Test Driven Development) using Jest.
• Security against NoSQL Injection, XSS, and DDoS attacks.
• Frontend built using React + Vite.

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Technologies Used

• Node.js + Express
• MongoDB
• JWT (Json Web Token)
• WebSocket
• React + Vite
• Jest (for unit testing)
• Helmet, Rate Limiting, and Mongo Sanitize for security

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Prerequisites

• Node.js installed
• MongoDB
• Copy .env.example to .env and configure it
• Copy frontend/.env.example to frontend/.env and configure it

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How to Run the Project

1. Install Dependencies

# Backend
cd project-3
npm install

# Frontend
cd frontend
npm install

2. Start Backend Nodes

Terminal 1 - Node 1 (Port 3001):

cd project-3
npm run node1

Terminal 2 - Node 2 (Port 3002) - Optional:

cd project-3
npm run node2

3. Start Frontend

Terminal 3:

cd project-3/frontend
npm run dev

Running Tests (Jest)

npm test

Assignment Requirements Coverage

Requirement	Status
Custom Blockchain	Done
Transaction Pool + Validation	Done
Mining + Reward Transaction	Done
Multi-node sync via WebSocket/HTTP	Done
MongoDB for users, transactions, blocks	Done
JWT-based user auth	Done
React + Vite Frontend	Done
Block & transaction lists	Done
Mining via UI	Done
TDD & Clean Code	Done
Security (XSS, NoSQL, RateLimit)	Done

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Author

Developed by Zoher Sahli – blockchain and full-stack developer student