Simple Blockchain

A minimal but complete blockchain implementation in Python with CLI and optional REST API.

Features

• SHA-256 hashing
• Proof-of-Work mining
• Transaction pool
• Chain validation
• Optional Flask REST API

Usage

CLI Mode (no dependencies)

python blockchain.py cli

Available commands: add <sender> <recipient> <amount>, mine, chain, validate, quit

Server Mode

pip install -r requirements.txt
python blockchain.py server

Endpoints: GET /chain, POST /transactions/new, GET /mine, GET /validate

How It Works

1. Transactions are submitted to a pending pool
2. Mining bundles pending transactions into a new block
3. Proof-of-Work requires the block hash to start with 0000
4. Each block references the previous block's hash, forming an immutable chain