def test_proof_of_work_invalid_nonce(self):
transactions_hash = self.mempool.hash([])
previous_block_hash = self.blockchain.hash(self.blockchain.last_block)
nonce = 12345
self.assertFalse(
ProofOfWork.valid_proof(transactions_hash, previous_block_hash,
nonce))
def test_proof_of_work(self):
transactions_hash = self.mempool.hash([])
previous_block_hash = self.blockchain.hash(self.blockchain.last_block)
nonce = ProofOfWork.proof_of_work(transactions_hash,
previous_block_hash)
encoded = f'{transactions_hash}{previous_block_hash}{nonce}'.encode()
hashed = hashlib.sha256(encoded).hexdigest()
self.assertEqual(hashed[:4], '0000')
self.assertTrue(
ProofOfWork.valid_proof(transactions_hash, previous_block_hash,
nonce))
def valid_chain(self, chain):
"""
Validate a given blockchain by checking the hash, the Proof of Work and the transactions for each block.
:param chain: <list> The blockchain
:return: <bool> True if valid, False if not
"""
previous_block = chain[0]
block_index = 1
while block_index < len(chain):
current_block = chain[block_index]
# Validate the hash of the block
if current_block['previous_block_hash'] != self.hash(
previous_block):
return False
# Validate the Proof of Work
if not ProofOfWork.valid_proof(current_block['transactions_hash'],
self.hash(previous_block),
current_block['nonce']):
return False
# Validate the transactions of the block
if current_block['transactions']:
coinbase_transactions = 0
for current_transaction in current_block['transactions']:
# Count the amount of coinbase transactions in the block
if current_transaction['sender'] == "0":
coinbase_transactions += 1
if not self.valid_transaction(current_transaction, chain,
block_index):
return False
# If the block contains more than one coinbase transaction return False
if coinbase_transactions > 1:
return False
previous_block = current_block
block_index += 1
return True