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Merge pull request #2 from luishsr/Corrections
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Corrections
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luishsr authored Feb 10, 2023
2 parents 9572760 + 75142f8 commit 2476ace
Showing 1 changed file with 186 additions and 82 deletions.
268 changes: 186 additions & 82 deletions blockchain.py
Original file line number Diff line number Diff line change
@@ -1,53 +1,105 @@
import hashlib
import json

from time import time
from urllib.parse import urlparse
from uuid import uuid4

from flask import Flask
from flask import Flask, jsonify, request


class Blockchain(object):
class Blockchain:
def __init__(self):
self.chain = []
self.current_transactions = []
self.chain = []
self.nodes = set()

# Create the genesis block
self.new_block(previous_hash=1, proof=100)
self.new_block(previous_hash='1', proof=100)

def proof_of_work(self, last_proof):
def register_node(self, address):
"""
Simple Proof of Work Algorithm:
- Find a number p' such that hash(pp') contains leading 4 zeroes, where p is the previous p'
- p is the previous proof, and p' is the new proof
:param last_proof: <int>
:return: <int>
Add a new node to the list of nodes
:param address: Address of node. Eg. 'http://192.168.0.5:5000'
"""

proof = 0
while self.valid_proof(last_proof, proof) is False:
proof += 1
parsed_url = urlparse(address)
if parsed_url.netloc:
self.nodes.add(parsed_url.netloc)
elif parsed_url.path:
# Accepts an URL without scheme like '192.168.0.5:5000'.
self.nodes.add(parsed_url.path)
else:
raise ValueError('Invalid URL')

return proof

@staticmethod
def valid_proof(last_proof, proof):
def valid_chain(self, chain):
"""
Validates the Proof: Does hash(last_proof, proof) contain 4 leading zeroes?
:param last_proof: <int> Previous Proof
:param proof: <int> Current Proof
:return: <bool> True if correct, False if not.
Determine if a given blockchain is valid
:param chain: A blockchain
:return: True if valid, False if not
"""

guess = f'{last_proof}{proof}'.encode()
guess_hash = hashlib.sha256(guess).hexdigest()
return guess_hash[:4] == "0000"
last_block = chain[0]
current_index = 1

while current_index < len(chain):
block = chain[current_index]
print(f'{last_block}')
print(f'{block}')
print("\n-----------\n")
# Check that the hash of the block is correct
last_block_hash = self.hash(last_block)
if block['previous_hash'] != last_block_hash:
return False

def new_block(self, proof, previous_hash=None):
# Check that the Proof of Work is correct
if not self.valid_proof(last_block['proof'], block['proof'], last_block_hash):
return False

last_block = block
current_index += 1

return True

def resolve_conflicts(self):
"""
This is our consensus algorithm, it resolves conflicts
by replacing our chain with the longest one in the network.
:return: True if our chain was replaced, False if not
"""

neighbours = self.nodes
new_chain = None

# We're only looking for chains longer than ours
max_length = len(self.chain)

# Grab and verify the chains from all the nodes in our network
for node in neighbours:
response = requests.get(f'http://{node}/chain')

if response.status_code == 200:
length = response.json()['length']
chain = response.json()['chain']

# Check if the length is longer and the chain is valid
if length > max_length and self.valid_chain(chain):
max_length = length
new_chain = chain

# Replace our chain if we discovered a new, valid chain longer than ours
if new_chain:
self.chain = new_chain
return True

return False

def new_block(self, proof, previous_hash):
"""
Create a new Block in the Blockchain
:param proof: <int> The proof given by the Proof of Work algorithm
:param previous_hash: (Optional) <str> Hash of previous Block
:return: <dict> New Block
:param proof: The proof given by the Proof of Work algorithm
:param previous_hash: Hash of previous Block
:return: New Block
"""

block = {
Expand All @@ -67,10 +119,10 @@ def new_block(self, proof, previous_hash=None):
def new_transaction(self, sender, recipient, amount):
"""
Creates a new transaction to go into the next mined Block
:param sender: <str> Address of the Sender
:param recipient: <str> Address of the Recipient
:param amount: <int> Amount
:return: <int> The index of the Block that will hold this transaction
:param sender: Address of the Sender
:param recipient: Address of the Recipient
:param amount: Amount
:return: The index of the Block that will hold this transaction
"""
self.current_transactions.append({
'sender': sender,
Expand All @@ -88,32 +140,48 @@ def last_block(self):
def hash(block):
"""
Creates a SHA-256 hash of a Block
:param block: <dict> Block
:return: <str>
:param block: Block
"""

# We must make sure that the Dictionary is Ordered, or we'll have inconsistent hashes
block_string = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(block_string).hexdigest()

def new_transaction(self, sender, recipient, amount):
def proof_of_work(self, last_block):
"""
Creates a new transaction to go into the next mined Block
:param sender: <str> Address of the Sender
:param recipient: <str> Address of the Recipient
:param amount: <int> Amount
:return: <int> The index of the Block that will hold this transaction
Simple Proof of Work Algorithm:
- Find a number p' such that hash(pp') contains leading 4 zeroes
- Where p is the previous proof, and p' is the new proof
:param last_block: <dict> last Block
:return: <int>
"""

self.current_transactions.append({
'sender': sender,
'recipient': recipient,
'amount': amount,
})
last_proof = last_block['proof']
last_hash = self.hash(last_block)

proof = 0
while self.valid_proof(last_proof, proof, last_hash) is False:
proof += 1

return proof

@staticmethod
def valid_proof(last_proof, proof, last_hash):
"""
Validates the Proof
:param last_proof: <int> Previous Proof
:param proof: <int> Current Proof
:param last_hash: <str> The hash of the Previous Block
:return: <bool> True if correct, False if not.
"""

return self.last_block['index'] + 1
guess = f'{last_proof}{proof}{last_hash}'.encode()
guess_hash = hashlib.sha256(guess).hexdigest()
return guess_hash[:4] == "0000"

# Instantiate our Node

# Instantiate the Node
app = Flask(__name__)

# Generate a globally unique address for this node
Expand All @@ -125,22 +193,31 @@ def new_transaction(self, sender, recipient, amount):

@app.route('/mine', methods=['GET'])
def mine():
return "We'll mine a new Block"

@app.route('/transactions/new', methods=['POST'])
def new_transaction():
return "We'll add a new transaction"
# We run the proof of work algorithm to get the next proof...
last_block = blockchain.last_block
proof = blockchain.proof_of_work(last_block)

# We must receive a reward for finding the proof.
# The sender is "0" to signify that this node has mined a new coin.
blockchain.new_transaction(
sender="0",
recipient=node_identifier,
amount=1,
)

# Forge the new Block by adding it to the chain
previous_hash = blockchain.hash(last_block)
block = blockchain.new_block(proof, previous_hash)

@app.route('/chain', methods=['GET'])
def full_chain():
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain),
'message': "New Block Forged",
'index': block['index'],
'transactions': block['transactions'],
'proof': block['proof'],
'previous_hash': block['previous_hash'],
}
return jsonify(response), 200

if __name__ == '__main__':
app.run(host='0.0.0.0', port=5000)

@app.route('/transactions/new', methods=['POST'])
def new_transaction():
Expand All @@ -155,33 +232,60 @@ def new_transaction():
index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'])

response = {'message': f'Transaction will be added to Block {index}'}
return jsonify(response), 201

@app.route('/mine', methods=['GET'])
def mine():
# We run the proof of work algorithm to get the next proof...
last_block = blockchain.last_block
last_proof = last_block['proof']
proof = blockchain.proof_of_work(last_proof)
return jsonify(response), 201

# We must receive a reward for finding the proof.
# The sender is "0" to signify that this node has mined a new coin.
blockchain.new_transaction(
sender="0",
recipient=node_identifier,
amount=1,
)

# Forge the new Block by adding it to the chain
previous_hash = blockchain.hash(last_block)
block = blockchain.new_block(proof, previous_hash)
@app.route('/chain', methods=['GET'])
def full_chain():
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain),
}
return jsonify(response), 200


@app.route('/nodes/register', methods=['POST'])
def register_nodes():
values = request.get_json()

nodes = values.get('nodes')
if nodes is None:
return "Error: Please supply a valid list of nodes", 400

for node in nodes:
blockchain.register_node(node)

response = {
'message': "New Block Forged",
'index': block['index'],
'transactions': block['transactions'],
'proof': block['proof'],
'previous_hash': block['previous_hash'],
'message': 'New nodes have been added',
'total_nodes': list(blockchain.nodes),
}
return jsonify(response), 201


@app.route('/nodes/resolve', methods=['GET'])
def consensus():
replaced = blockchain.resolve_conflicts()

if replaced:
response = {
'message': 'Our chain was replaced',
'new_chain': blockchain.chain
}
else:
response = {
'message': 'Our chain is authoritative',
'chain': blockchain.chain
}

return jsonify(response), 200


if __name__ == '__main__':
from argparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument('-p', '--port', default=5000, type=int, help='port to listen on')
args = parser.parse_args()
port = args.port

return jsonify(response), 200
app.run(host='0.0.0.0', port=port)

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