Python Blockchain Implementation

A simple blockchain implementation in Python using Flask as the web framework. This project demonstrates the core concepts of blockchain technology including proof-of-work, transaction recording, and decentralized consensus.

Features

• Blockchain Core

  • Genesis block creation
  • Proof-of-work algorithm (with adjustable difficulty)
  • Block creation and chaining
  • Hashing with SHA-256

• Transaction System

  • New transaction creation
  • Transaction recording in blocks
  • Mining rewards

• Network Features

  • Node registration
  • Consensus algorithm (longest chain rule)
  • Conflict resolution

• API Endpoints

  • Mine new blocks
  • Create transactions
  • View blockchain
  • Register nodes
  • Resolve chain conflicts

Installation

1. Clone the repository:

   git clone https://github.com/yourusername/python-blockchain.git
   cd python-blockchain
   

2. Install the required dependencies:

   pip install flask requests uuid
   

3. Runt the blockchain node:

   python blockchain.py
   

API Documentation

Mine a new block

• Endpoint: GET /mine
• Description: Mines a new block and awards the miner (node) with 1 coin
• Response: Returns the newly mined block details

Create a new transaction

• Endpoint: POST /transactions/new
• Body:

{
  "sender": "sender_address",
  "recipient": "recipient_address",
  "amount": 1
}

• Description: Creates a new transaction to be added to the next mined block
• Response: Returns the block index the transaction will be included in

Get full blockchain

• Endpoint: GET /chain
• Description: Returns the full blockchain and its length
• Response:

{
  "chain": [...],
  "length": n
}

Register new nodes

• Endpoint: POST /nodes/register
• Body:

{
  "nodes": ["http://node1:5000", "http://node2:5000"]
}

• Description: Registers new nodes with the network
• Response: Returns list of all registered nodes

Consensus

• Endpoint: GET /nodes/resolve
• Description: Resolves blockchain conflicts by choosing the longest valid chain
• Response: Returns the current chain (either replaced or authoritative)

Running Multiple Nodes

To create a decentralized network:

1. Run multiple instances on different ports:

    python blockchain.py -p 5001
    python blockchain.py -p 5002

2. Register nodes with each other(example with Curl):

   curl -X POST -H "Content-Type: application/json" -d '{
    "nodes": ["http://localhost:5000"]
    }' "http://localhost:5001/nodes/register"

Configuration

• The proof-of-work difficulty can be adjusted by modifying the valid_proof method (change the numbef of leading zeroes required)
• Mining reward amount is hardcoded to 1 coin (can be changed in the /mine endpoint)

Dependencies

• Python 3.x
• Flask
• Requests
• UUID