A fully functional blockchain implementation in Python featuring digital signatures, transaction fees, Merkle trees, and a complete REST API.

• ⛏️ Proof of Work Mining - SHA-256 based mining with adjustable difficulty
• 🔐 Digital Signatures - RSA-2048 signing for transaction security
• 💰 Transaction Fees - Economic model with mining rewards
• 🌳 Merkle Trees - Efficient transaction verification (Bitcoin SPV)
• 🌐 REST API - Complete HTTP API for blockchain interaction
• 💾 Persistence - Save/load blockchain to disk

# Clone the repository
git clone https://github.com/yourusername/python-blockchain.git
cd python-blockchain

# Install dependencies
pip3 install -r requirements.txt

# Run the blockchain API
python3 blockchain.py

The API server will start at http://127.0.0.1:5000

# In a new terminal

# Check API status
curl http://127.0.0.1:5000/

# Mine first block (Alice gets coins)
curl -X POST http://127.0.0.1:5000/mine \
  -H "Content-Type: application/json" \
  -d '{"miner": "alice"}'

# Check Alice's balance
curl http://127.0.0.1:5000/balance/alice

# Create a transaction
curl -X POST http://127.0.0.1:5000/transaction \
  -H "Content-Type: application/json" \
  -d '{"sender": "alice", "recipient": "bob", "amount": 5, "fee": 1}'

# Mine the transaction
curl -X POST http://127.0.0.1:5000/mine \
  -H "Content-Type: application/json" \
  -d '{"miner": "bob"}'

Blockchain
├── Block[]
│   ├── Transaction[] (with RSA signatures)
│   └── MerkleTree (for verification)
└── Wallet[] (RSA key pairs)

• Digital Signatures: RSA-2048 with PSS padding
• Hashing: SHA-256 for all cryptographic operations
• Proof of Work: Adjustable difficulty consensus
• Merkle Trees: Efficient transaction verification
• Tamper Detection: Any modification invalidates the chain

# Test the blockchain
python3 blockchain.py

# In another terminal, run API tests
curl http://127.0.0.1:5000/blockchain/stats

• Difficulty 2: ~0.01s per block
• Difficulty 3: ~0.1s per block
• Difficulty 4: ~0.5s per block
• Signature Verification: <1ms per transaction

This project shows understanding of:

✅ Blockchain fundamentals (blocks, chains, mining)
✅ Cryptography (RSA signatures, SHA-256 hashing)
✅ Proof of Work consensus
✅ Transaction processing and validation
✅ Balance tracking and fee economics
✅ Merkle tree data structures
✅ REST API development

• Python 3.8+ - Core language
• Flask - Web framework for REST API
• cryptography - RSA signatures and key management
• hashlib - SHA-256 hashing

MIT License - see LICENSE file for details.

**Yamini Desai Nyalakonda **

• GitHub: @yaminidesai

• Bitcoin Whitepaper by Satoshi Nakamoto
• Inspired by Bitcoin and Ethereum implementations
• Built for educational purposes

⭐ If you found this helpful for learning blockchain, please star it!