A production-ready, enterprise-grade blockchain implementation built with Node.js, featuring advanced security, real-time capabilities, and comprehensive monitoring.

• ⛏️ Proof of Work Mining - Configurable difficulty consensus
• 💸 Digital Transactions - Cryptographically signed with secp256k1
• 🔗 Chain Validation - Complete integrity verification
• 🌍 Multi-Node Network - Distributed blockchain synchronization

• 🔐 Encrypted Key Storage - AES-256-GCM encryption with PBKDF2
• 🛡️ Multi-Layer Protection - Input sanitization, rate limiting, CSRF protection
• 🔍 Real-Time Monitoring - Integrity monitoring and threat detection
• 📊 Complete Audit Trail - All operations logged with timestamps
• ⚡ Attack Prevention - DoS protection, injection prevention, mining spam protection

• 📡 WebSocket Real-Time Updates - Live transaction and mining notifications
• 📈 Performance Metrics - System monitoring and analytics
• 🏥 Health Monitoring - Comprehensive node status tracking
• 💾 Data Persistence - Blockchain state survives restarts
• 🔄 Graceful Operations - Proper startup, shutdown, and error recovery

┌─────────────────┐    ┌──────────────────┐    ┌─────────────────┐
│   Client Apps   │    │   WebSocket      │    │   REST API      │
│                 │    │   Real-time      │    │   HTTP/HTTPS    │
└─────┬───────────┘    └────────┬─────────┘    └─────┬───────────┘
      │                         │                    │
      └─────────────────────────┼────────────────────┘
                                │
                    ┌───────────▼───────────┐
                    │    Express Server     │
                    │   Security Layer      │
                    └───────────┬───────────┘
                                │
        ┌───────────────────────┼───────────────────────┐
        │                       │                       │
┌───────▼────────┐    ┌─────────▼────────┐    ┌─────────▼────────┐
│  Blockchain     │    │   Security       │    │   Monitoring     │
│  Core Engine    │    │   Services       │    │   & Metrics      │
│                 │    │                  │    │                  │
│ • Proof of Work │    │ • Key Management │    │ • Performance    │
│ • Transactions  │    │ • Audit Logging  │    │ • Health Checks  │
│ • Validation    │    │ • Rate Limiting  │    │ • Real-time Data │
│ • P2P Network   │    │ • Input Sanitize │    │ • Error Tracking │
└─────────────────┘    └──────────────────┘    └──────────────────┘

• Node.js 14+ (18+ recommended)
• Git
• Terminal/Command Prompt

# Clone the repository
git clone <repository-url>
cd "Blockchain Node 1"

# Install dependencies
npm install

# Create secure directory (Linux/macOS)
mkdir -p server/secure && chmod 700 server/secure

# Create secure directory (Windows)
mkdir server\secure

# Run security check
npm run security-check

# Start development server
npm run serve

# The blockchain node will be running at http://localhost:8001

# Security validation and production start
npm run production

# Or manual production setup
NODE_ENV=production npm start

Most endpoints are public for development. In production, implement proper authentication.

GET /api/health

Returns node status, blockchain info, and system metrics.

GET /api/generateKeys

Creates a new cryptographic keypair for blockchain transactions.

POST /api/transactionCreate
Content-Type: application/json

{
  "recipient": "04a1b2c3d4e5f6...", 
  "amount": 10.5
}

GET /api/minePendingTxs

Processes pending transactions into a new block using Proof of Work.

GET /api/chainList

Returns the complete blockchain with all blocks and transactions.

GET /api/chainValidation

Verifies the cryptographic integrity of the entire blockchain.

# Connect to other nodes
POST /api/nodeConnection
{
  "nodes": ["http://node2:8001", "http://node3:8001"]
}

# Synchronize with network
GET /api/chainSync

# Get statistics
GET /api/stats

const ws = new WebSocket('ws://localhost:8001');

ws.onmessage = function(event) {
    const data = JSON.parse(event.data);
    console.log('Real-time update:', data.type, data.data);
};

h:\Blockchain\Node 1\
├── server/
│   ├── app/
│   │   ├── Blockchain/           # Core blockchain logic
│   │   │   ├── Block.js         # Block structure and mining
│   │   │   ├── Blockchain.js    # Main blockchain class
│   │   │   ├── Transaction.js   # Transaction handling
│   │   │   ├── Validation.js    # Chain validation logic
│   │   │   └── Network.js       # P2P networking
│   │   ├── Controllers/         # API endpoint handlers
│   │   │   ├── BlockchainController.js
│   │   │   └── WalletController.js
│   │   └── Middleware/          # Express middleware
│   │       └── ErrorMiddleware.js
│   ├── config/                  # Configuration files
│   │   └── blockchain.js        # Blockchain parameters
│   ├── controllers/             # Advanced controllers
│   │   └── StatsController.js   # Analytics and metrics
│   ├── middleware/              # Security and validation
│   │   ├── security.js          # Security middleware
│   │   ├── validation.js        # Input validation
│   │   ├── rateLimiter.js      # Rate limiting
│   │   └── enhancedValidation.js
│   ├── routes/                  # API routes
│   │   ├── api.js              # Main API routes
│   │   └── docs.js             # Documentation routes
│   ├── utils/                   # Utility functions
│   │   ├── logger.js           # Logging system
│   │   ├── metrics.js          # Performance metrics
│   │   ├── persistence.js      # Data storage
│   │   ├── websocket.js        # WebSocket handling
│   │   ├── secureKeyManager.js # Cryptographic key management
│   │   ├── integrityMonitor.js # Security monitoring
│   │   ├── auditLogger.js      # Audit trail
│   │   ├── configValidator.js  # Configuration validation
│   │   └── processMonitor.js   # Process management
│   └── server.js               # Main server file
├── scripts/                    # Utility scripts
│   ├── runTests.js            # Automated testing
│   ├── securityCheck.js       # Security validation
│   └── production-start.js    # Production launcher
├── .env                       # Environment configuration
├── .gitignore                # Git ignore rules
├── package.json              # Node.js dependencies
├── README.md                 # This file
├── TESTING.md               # Testing guide
└── ARCHITECTURE.md          # Detailed architecture

class Block {
  constructor(timestamp, transactions, previousHash) {
    this.timestamp = timestamp;
    this.transactions = transactions;
    this.previousHash = previousHash;
    this.hash = this.calculateHash();
    this.nonce = 0; // For proof of work
  }
  
  // Proof of work mining
  mineBlock(difficulty) { ... }
  
  // SHA256 hash calculation
  calculateHash() { ... }
  
  // Validate all transactions in block
  hasValidTransactions() { ... }
}

class Blockchain {
  constructor() {
    this.chain = [this.createGenesisBlock()];
    this.difficulty = 2;
    this.pendingTransactions = [];
    this.miningReward = 100;
    this.nodes = [];
  }
  
  // Add new transactions
  addTransaction(transaction) { ... }
  
  // Mine pending transactions
  minePendingTransactions(miningRewardAddress) { ... }
  
  // Validate entire chain
  isChainValid() { ... }
  
  // Network synchronization
  replaceChain() { ... }
}

class Transaction {
  constructor(fromAddress, toAddress, amount) {
    this.fromAddress = fromAddress;
    this.toAddress = toAddress;
    this.amount = amount;
    this.timestamp = Date.now();
  }
  
  // Sign with private key
  signTransaction(keyPair) { ... }
  
  // Verify signature
  isValid() { ... }
  
  // Calculate transaction hash
  calculateHash() { ... }
}

• Elliptic Curve Cryptography: secp256k1 for transaction signatures
• SHA-256 Hashing: For block and transaction integrity
• Proof of Work: Prevents spam and ensures consensus
• Key Encryption: AES-256-GCM with PBKDF2 key derivation

• Rate Limiting: Prevents DoS attacks (5 tx/min, 2 mining/min)
• Input Sanitization: XSS and injection protection
• Request Size Limits: 50MB maximum request size
• IP-based Controls: Production access restrictions

• Audit Logging: Every operation logged with timestamps
• Integrity Monitoring: Real-time tamper detection
• Secure Storage: Encrypted key files with restricted permissions
• Graceful Shutdown: Proper state saving on exit

# Security validation
npm run security-check

# Automated test suite
node scripts/runTests.js

# Manual API testing (see TESTING.md)
curl http://localhost:8001/api/health

• ✅ Core blockchain functionality
• ✅ Transaction creation and validation
• ✅ Block mining and proof of work
• ✅ Chain synchronization
• ✅ Security features and rate limiting
• ✅ WebSocket real-time updates
• ✅ Error handling and recovery

See TESTING.md for comprehensive testing guide.

# .env file
NODE_ENV=development          # development | production
PORT=8001                    # Server port
SECURE_KEY_STORAGE=true      # Enable encrypted key storage
ENABLE_KEY_GENERATION=true   # Auto-generate keys on startup

// server/config/blockchain.js
module.exports = {
  DIFFICULTY: 2,              // Mining difficulty
  MINING_REWARD: 100,         # Reward per mined block
  MAX_PENDING_TRANSACTIONS: 100,
  MAX_BLOCK_SIZE: 10,
  RATE_LIMIT: {
    TRANSACTION: { max: 5, window: 60000 },
    MINING: { max: 2, window: 60000 }
  }
};

• Transaction throughput (tx/second)
• Block mining time (seconds)
• Memory usage (MB)
• Network latency (ms)
• Error rates (%)

# Real-time health check
curl http://localhost:8001/api/health

# Detailed statistics  
curl http://localhost:8001/api/stats

# System metrics
curl http://localhost:8001/api/health | jq '.system'

# View recent activity
tail -f server/logs/audit.log

# Search specific events
grep "TRANSACTION_CREATED" server/logs/audit.log
grep "SECURITY_EVENT" server/logs/audit.log

# Start nodes on different ports
PORT=8001 npm start &  # Node 1
PORT=8002 npm start &  # Node 2
PORT=8003 npm start &  # Node 3

# Connect nodes together
curl -X POST http://localhost:8001/api/nodeConnection \
  -H "Content-Type: application/json" \
  -d '{"nodes": ["http://localhost:8002", "http://localhost:8003"]}'

# Synchronize chains
curl http://localhost:8001/api/chainSync

     Node 1 (8001) ←→ Node 2 (8002)
           ↕               ↕
     Node 4 (8004) ←→ Node 3 (8003)

We welcome contributions! Here's how to get started:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Run tests (npm run security-check && node scripts/runTests.js)
4. Commit changes (git commit -m 'Add amazing feature')
5. Push to branch (git push origin feature/amazing-feature)
6. Create a Pull Request

• Follow existing code style and patterns
• Add comprehensive tests for new features
• Update documentation for API changes
• Ensure all security checks pass
• Add audit logging for new operations

• Never commit private keys or sensitive data
• All user inputs must be validated and sanitized
• New endpoints require rate limiting consideration
• Security-related changes need thorough review
• Always run security checks before submission

• Environment variables configured
• SSL/TLS certificates installed
• Firewall rules configured
• Log rotation setup
• Monitoring alerts configured
• Backup strategy implemented
• Security audit completed

FROM node:18-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
RUN mkdir -p server/secure && chmod 700 server/secure
EXPOSE 8001
CMD ["npm", "run", "production"]

server {
    listen 443 ssl;
    server_name blockchain.example.com;
    
    ssl_certificate /path/to/cert.pem;
    ssl_certificate_key /path/to/key.pem;
    
    location / {
        proxy_pass http://localhost:8001;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }
}

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

• Elliptic Curve Cryptography: Built on the battle-tested elliptic library
• Express.js: Robust web framework for Node.js
• WebSocket: Real-time communication with ws library
• Security: Following OWASP security best practices
• Community: Thanks to all contributors and users

• Issues: GitHub Issues
• Discussions: GitHub Discussions
• Security: Report security issues privately to [email protected]
• Documentation: Full Documentation

⚠️ Production Notice: This blockchain implements enterprise-grade security. Always run comprehensive security checks before production deployment. Regular security audits are recommended.

🔒 Security First: This project prioritizes security and follows industry best practices. All security-related contributions are thoroughly reviewed.

🌟 Star this repo if you find it useful! Your support helps us continue improving this open-source blockchain implementation.