🪙 SandiCoin - Cryptocurrency with Blockchain Network

Complete cryptocurrency implementation with blockchain, P2P networking, transaction validation, and mining system.

🚀 Quick Start for Testing

Prerequisites

• Node.js 18+
• MongoDB running on localhost:27017
• Two terminal windows

Start the Application

Terminal 1 - Backend:

cd backend
npm install
cp .env.example .env  # Copy environment configuration
npm run dev

Terminal 2 - Frontend:

cd frontend
npm install
npm run dev

Access: Open http://localhost:5173 in your browser

🛠️ Development Commands

# Start a new node (auto-assigns ports)
npm run dev

# Start specific nodes
npm run dev:node1  # Port 3000
npm run dev:node2  # Port 3001 
npm run dev:node3  # Port 3002
npm run dev:node4  # Port 3003

# Network management
npm run dev:status  # Check running nodes
npm run dev:kill    # Kill all nodes
npm run dev:reset   # Kill all nodes and reset network

🎯 Assignment Requirements ✅

Blockchain & Cryptocurrency

• ✅ Complete blockchain with transaction validation
• ✅ Transaction pool for pending transactions
• ✅ Mining with reward transactions
• ✅ Proof-of-work consensus mechanism

P2P Network

• ✅ Multi-node support (WebSocket-based)
• ✅ Automatic blockchain synchronization
• ✅ Transaction broadcasting across nodes

Database Integration

• ✅ MongoDB for blockchain, blocks, transactions, and users
• ✅ Persistent storage with automatic loading

Security (JWT Authentication)

• ✅ User registration and login required
• ✅ JWT token validation for API access
• ✅ Role-based access control
• ✅ Protection against NoSQL injection, XSS, DDoS

React Frontend Client

• ✅ User registration and authentication
• ✅ Create new transactions (send coins)
• ✅ View transaction history
• ✅ Browse blockchain and blocks
• ✅ Mine new blocks interface

TDD & Best Practices

• ✅ 67 passing tests for transaction handling
• ✅ Clean Code, SOC, MVC architecture
• ✅ TypeScript for type safety

🧪 Testing Features

1. Register & Login

• Create new account with email/password
• Login receives JWT token for API access

2. Send Transactions

• Send coins to other users (by email or wallet address)
• Transactions added to pool, confirmed when mined

3. Mine Blocks

• Click "Mine Block" to process pending transactions
• Receive mining reward (50 SandiCoins)

4. Multi-Node Network

# Start multiple backend nodes
cd backend && PORT=3001 npm run dev  # Node 1
cd backend && PORT=3002 npm run dev  # Node 2
cd backend && PORT=3003 npm run dev  # Node 3

5. View Blockchain

• Explore all blocks with transactions
• View network statistics and node information

🛠️ Technology Stack

• Backend: Node.js, TypeScript, Express, MongoDB, WebSockets, JWT
• Frontend: React, TypeScript, Vite, Axios
• Testing: Vitest (67 tests)
• Security: Input validation, CORS, rate limiting, sanitization

📊 API Endpoints

• POST /api/auth/register - User registration
• POST /api/auth/login - User login
• POST /api/transactions - Create transaction
• GET /api/transactions - View user transactions
• POST /api/mining/mine - Mine new block
• GET /api/blockchain - Get full blockchain

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Assignment: Kryptovaluta och nätverk - Backend Development Course
Author: Manuel Lopez
Features: All G and VG requirements implemented