Tommi Versetti
@tommiversetti
import hashlib import json from time import time from uuid import uuid4 class Blockchain: def __init__(self): self.chain = [] self.current_transactions = [] # Create the genesis block self.new_block(previous_hash='1', proof=100) def new_block(self, proof, previous_hash=None): """ 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 """ block = { 'index': len(self.chain) + 1, 'timestamp': time(), 'transactions': self.current_transactions, 'proof': proof, 'previous_hash': previous_hash or self.hash(self.chain[-1]), } # Reset the current list of transactions self.current_transactions = [] self.chain.append(block) return block
0 reply
0 recast
4 reactions
Tommi Versetti
@tommiversetti
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 """ self.current_transactions.append({ 'sender': sender, 'recipient': recipient, 'amount': amount, }) return self.last_block['index'] + 1 @staticmethod def hash(block): """ Creates a SHA-256 hash of a Block :param block: <dict> Block :return: <str> """ # 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() @property def last_block(self): return self.chain[-1]
0 reply
0 recast
0 reaction
Tommi Versetti
@tommiversetti
def proof_of_work(self, last_proof): """ 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> """ proof = 0 while self.valid_proof(last_proof, proof) is False: proof += 1 return proof @staticmethod def valid_proof(last_proof, proof): """ 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. """ guess = f'{last_proof}{proof}'.encode() guess_hash = hashlib.sha256(guess).hexdigest() return guess_hash[:4] == "0000"
0 reply
0 recast
0 reaction
