105 lines
3.3 KiB
Python
105 lines
3.3 KiB
Python
# Module 1 - Create a Blockchain
|
|
|
|
# To be installed:
|
|
# Flask==0.12.2: pip install Flask==0.12.2
|
|
# Postman HTTP Client: https://www.getpostman.com/
|
|
|
|
# Importing the libraries
|
|
import datetime
|
|
import hashlib
|
|
import json
|
|
from flask import Flask, jsonify
|
|
|
|
# Part 1 - Building a Blockchain
|
|
|
|
class Blockchain:
|
|
|
|
def __init__(self):
|
|
self.chain = []
|
|
self.create_block(proof = 1, previous_hash = '0')
|
|
|
|
def create_block(self, proof, previous_hash):
|
|
block = {'index': len(self.chain) + 1,
|
|
'timestamp': str(datetime.datetime.now()),
|
|
'proof': proof,
|
|
'previous_hash': previous_hash}
|
|
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
|
|
|
|
# Part 2 - Mining our Blockchain
|
|
|
|
# Creating a Web App
|
|
app = Flask(__name__)
|
|
|
|
# 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)
|
|
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']}
|
|
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
|
|
|
|
# Running the app
|
|
app.run(host = '0.0.0.0', port = 5000)
|