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This is the final version and all cases have been tested for this version. We tested the transaction request, the mining request, the request to send the last chain for the other nodes, and so on.
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Smart Blockchain - Block Producer
Created on Mon Mar 16 20:06:06 2020
@author: Somayyeh & Mehran
Mine: Whenever you instruct
Port: 5000
In “Smart Blockchain”, one or more block producers smart contract (BPSC) is present in the network,
and no successful transaction is performed without BPSC involvement. For a successful transaction
in the network, first, the sender must send the cryptocurrency to the wallet of BPSC and then BPSC
sends cryptocurrency automatically to the receiver. This simple action has led the BPSC to have all
network transactions’ data accurately and flawlessly and then as an accurate and trust financial
institution, record transactions’ data into a new block and add this new block to the end of the
blockchain so there would be no task for miners in “Smart Blockchain”.
import hashlib
import json
from time import time
from urllib.parse import urlparse
import requests
from flask import Flask, jsonify, request
class Smart_Blockchain:
def __init__(self):
self.current_transactions = []
self.chain = []
self.nodes = set()
# Create the genesis block
def register_node(self, address):
Add a new node to the list of nodes
:param address: Address of node. Eg. ''
parsed_url = urlparse(address)
if parsed_url.netloc:
elif parsed_url.path:
# Accepts an URL without scheme like ''.
raise ValueError('Invalid URL')
def smart_chain(self):
All nodes can receive the smart_chain
schain = None
response = requests.get(f'')
if response.status_code == 200:
chain = response.json()['chain']
schain = chain
# Replace our chain
if schain:
self.chain = schain
return True
return False
def new_block(self, previous_hash):
Create a new Block in the Smart Blockchain
:param previous_hash: Hash of previous Block
:return: New Block
block = {
'index': len(self.chain) + 1,
'timestamp': time(),
'transactions': self.current_transactions,
'previous_hash': previous_hash or self.hash(self.chain[-1]),
# Reset the current list of transactions
self.current_transactions = []
return block
def new_transaction(self, sender, amount, recipient):
Creates a new transaction to go into the next mined Block
:param sender: Address of the Sender
:param amount_send: The amount sent by the sender
:param bpsc: Address of the Smart contract (bpsc)
:param amount_bpsc: The amount received by bpsc (Transaction fees)
:param recipient: Address of the Recipient
:param amount_receive: The amount received by the recipient
:return: The index of the Block that will hold this transaction
'sender': sender,
'amount_send': amount,
'bpsc': 'bpsc_wallet_address', # Block Producer Smart Contract (bpsc)
'amount_bpsc': amount * 0.00005, # Transaction fees
'recipient': recipient,
'amount_receive': amount * 0.99995,
return self.last_block['index'] + 1
def last_block(self):
return self.chain[-1]
def hash(block):
Creates a SHA-256 hash of a Block
: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()
# Instantiate the Node
app = Flask(__name__)
# Instantiate the Smart_Blockchain
blockchain = Smart_Blockchain()
@app.route('/mine', methods=['GET'])
def mine():
last_block = blockchain.last_block
# Forge the new Block by adding it to the chain
previous_hash = blockchain.hash(last_block)
block = blockchain.new_block(previous_hash)
response = {
'message': "New Block Forged",
'index': block['index'],
'transactions': block['transactions'],
'previous_hash': block['previous_hash'],
return jsonify(response), 200
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
values = request.get_json()
# Check that the required fields are in the POST'ed data
required = ['sender', 'amount', 'recipient']
if not all(k in values for k in required):
return 'Missing values', 400
# Create a new Transaction
index = blockchain.new_transaction(values['sender'], values['amount'], values['recipient'])
response = {'message': f'Transaction will be added to Block {index}'}
return jsonify(response), 201
@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:
response = {
'message': 'New nodes have been added',
'total_nodes': list(blockchain.nodes),
return jsonify(response), 201
@app.route('/smart/chain', methods=['GET'])
def smart_chain():
replaced = blockchain.smart_chain()
if replaced:
response = {
'message': 'Smart chain update by bpsc',
'smart chain': blockchain.chain,
'length': len(blockchain.chain)
response = {
'message': 'Unsuccessful: Please try again',
'old chain': blockchain.chain,
'length': len(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'', port=port)