hadcoin.py
# Module 2 - Create a Cryptocurrency
# To be installed:
# Flask==0.12.2: pip install Flask==0.12.2
# Postman HTTP Client: https://www.getpostman.com/
# requests==2.18.4: pip install requests==2.18.4
# Importing the libraries
import datetime
import hashlib
import json
from flask import Flask, jsonify, request
import requests
from uuid import uuid4
from urllib.parse import urlparse
# Part 1 - Building a Blockchain
class Blockchain:
def __init__(self):
self.chain = []
self.transactions = []
self.create_block(proof = 1, previous_hash = '0')
self.nodes = set()
def create_block(self, proof, previous_hash):
block = {'index': len(self.chain) + 1,
'timestamp': str(datetime.datetime.now()),
'proof': proof,
'previous_hash': previous_hash,
'transactions': self.transactions}
self.transactions = []
self.chain.append(block)
return block
def get_previous_block(self):
return self.chain[-1]
def proof_of_work(self, previous_proof):
new_proof = 1
check_proof = False
while check_proof is False:
hash_operation = hashlib.sha256(str(new_proof**2 - previous_proof**2).encode()).hexdigest()
if hash_operation[:4] == '0000':
check_proof = True
else:
new_proof += 1
return new_proof
def hash(self, block):
encoded_block = json.dumps(block, sort_keys = True).encode()
return hashlib.sha256(encoded_block).hexdigest()
def is_chain_valid(self, chain):
previous_block = chain[0]
block_index = 1
while block_index < len(chain):
block = chain[block_index]
if block['previous_hash'] != self.hash(previous_block):
return False
previous_proof = previous_block['proof']
proof = block['proof']
hash_operation = hashlib.sha256(str(proof**2 - previous_proof**2).encode()).hexdigest()
if hash_operation[:4] != '0000':
return False
previous_block = block
block_index += 1
return True
def add_transaction(self, sender, receiver, amount):
self.transactions.append({'sender': sender,
'receiver': receiver,
'amount': amount})
previous_block = self.get_previous_block()
return previous_block['index'] + 1
def add_node(self, address):
parsed_url = urlparse(address)
self.nodes.add(parsed_url.netloc)
def replace_chain(self):
network = self.nodes
longest_chain = None
max_length = len(self.chain)
for node in network:
response = requests.get(f'http://{node}/get_chain')
if response.status_code == 200:
length = response.json()['length']
chain = response.json()['chain']
if length > max_length and self.is_chain_valid(chain):
max_length = length
longest_chain = chain
if longest_chain:
self.chain = longest_chain
return True
return False
# Part 2 - Mining our Blockchain
# Creating a Web App
app = Flask(__name__)
# Creating an address for the node on Port 5000
node_address = str(uuid4()).replace('-', '')
# Creating a Blockchain
blockchain = Blockchain()
# Mining a new block
@app.route('/mine_block', methods = ['GET'])
def mine_block():
previous_block = blockchain.get_previous_block()
previous_proof = previous_block['proof']
proof = blockchain.proof_of_work(previous_proof)
previous_hash = blockchain.hash(previous_block)
blockchain.add_transaction(sender = node_address, receiver = 'Hadelin', amount = 1)
block = blockchain.create_block(proof, previous_hash)
response = {'message': 'Congratulations, you just mined a block!',
'index': block['index'],
'timestamp': block['timestamp'],
'proof': block['proof'],
'previous_hash': block['previous_hash'],
'transactions': block['transactions']}
return jsonify(response), 200
# Getting the full Blockchain
@app.route('/get_chain', methods = ['GET'])
def get_chain():
response = {'chain': blockchain.chain,
'length': len(blockchain.chain)}
return jsonify(response), 200
# Checking if the Blockchain is valid
@app.route('/is_valid', methods = ['GET'])
def is_valid():
is_valid = blockchain.is_chain_valid(blockchain.chain)
if is_valid:
response = {'message': 'All good. The Blockchain is valid.'}
else:
response = {'message': 'Houston, we have a problem. The Blockchain is not valid.'}
return jsonify(response), 200
# Adding a new transaction to the Blockchain
@app.route('/add_transaction', methods = ['POST'])
def add_transaction():
json = request.get_json()
transaction_keys = ['sender', 'receiver', 'amount']
if not all(key in json for key in transaction_keys):
return 'Some elements of the transaction are missing', 400
index = blockchain.add_transaction(json['sender'], json['receiver'], json['amount'])
response = {'message': f'This transaction will be added to Block {index}'}
return jsonify(response), 201
# Part 3 - Decentralizing our Blockchain
# Connecting new nodes
@app.route('/connect_node', methods = ['POST'])
def connect_node():
json = request.get_json()
nodes = json.get('nodes')
if nodes is None:
return "No node", 400
for node in nodes:
blockchain.add_node(node)
response = {'message': 'All the nodes are now connected. The Hadcoin Blockchain now contains the following nodes:',
'total_nodes': list(blockchain.nodes)}
return jsonify(response), 201
# Replacing the chain by the longest chain if needed
@app.route('/replace_chain', methods = ['GET'])
def replace_chain():
is_chain_replaced = blockchain.replace_chain()
if is_chain_replaced:
response = {'message': 'The nodes had different chains so the chain was replaced by the longest one.',
'new_chain': blockchain.chain}
else:
response = {'message': 'All good. The chain is the largest one.',
'actual_chain': blockchain.chain}
return jsonify(response), 200
# Running the app
app.run(host = '0.0.0.0', port = 5000)node.json
{
"nodes": ["http://127.0.0.1:5001",
"http://127.0.0.1:5002",
"http://127.0.0.1:5003"]
}transaction.jsaon
{
"sender": "",
"receiver": "",
"amount":
}
🐣🐥