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