def test_block_initialize(self):
wallet = Wallet()
transaction = Transaction(wallet.pubkey, "CityU", 1)
signature = wallet.sign_transaction(transaction)
transaction.add_signature(signature)
block = Block(0, [transaction], datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), "0")
self.assertIsInstance(block, Block)
def test_block_compute_hash(self):
wallet = Wallet()
transaction = Transaction(wallet.pubkey, "CityU", 1)
signature = wallet.sign_transaction(transaction)
transaction.add_signature(signature)
block = Block(0, [transaction.to_json()], datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), "0")
hash_val = block.compute_hash()
self.assertIsInstance(hash_val, str)
self.assertGreater(len(hash_val), 0)
def test_block_to_json(self):
wallet = Wallet()
transaction = Transaction(wallet.pubkey, "CityU", 1)
signature = wallet.sign_transaction(transaction)
transaction.add_signature(signature)
block = Block(0, [transaction.to_json()], datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), "0")
content = block.to_json()
self.assertIsInstance(content, str)
self.assertGreater(len(content), 0)
def test_block_to_dict(self):
wallet = Wallet()
transaction = Transaction(wallet.pubkey, "CityU", 1)
signature = wallet.sign_transaction(transaction)
transaction.add_signature(signature)
block = Block(0, [transaction.to_json()], datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), "0")
content = block.to_dict()
self.assertIsInstance(content, dict)
self.assertEqual(list(content.keys()), ["index", "timestamp", "previous_hash", "merkle_root", "nonce", "difficulty"])
def create_genesis_block(self, wallet: Wallet):
'''method to create and puts the genesis block into the blockchain'''
block_reward = Transaction("Block_Reward", wallet.pubkey,
"5.0").to_json()
genesis_block = Block(
0, [block_reward],
datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), "0")
# Hash of genesis block cannot be computed directly, proof of work is needed
genesis_block.hash = self.proof_of_work(genesis_block)
self.chain.append(genesis_block.to_json())
def test_blockchain_add_block_wrong_previous_hash(self):
wallet = Wallet()
blockchain = Blockchain(wallet)
transaction = Transaction(wallet.pubkey, "CityU", 1)
signature = wallet.sign_transaction(transaction)
transaction.add_signature(signature)
block = Block(0, [transaction.to_json()], datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), "Wrong")
computed_hash = blockchain.proof_of_work(block)
result = blockchain.add_block(block, computed_hash)
self.assertFalse(result)
def test_blockchain_proof_of_work_bad_block(self):
wallet = Wallet()
blockchain = Blockchain(wallet)
transaction = Transaction(wallet.pubkey, "CityU", 1)
signature = wallet.sign_transaction(transaction)
transaction.add_signature(signature)
previous_hash = blockchain.last_block["hash"]
block = Block(0, [transaction.to_json()], datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), previous_hash)
delattr(block, "transaction")
self.assertRaises(AttributeError, blockchain.proof_of_work, block)
def test_blockchain_proof_of_work(self):
wallet = Wallet()
blockchain = Blockchain(wallet)
transaction = Transaction(wallet.pubkey, "CityU", 1)
signature = wallet.sign_transaction(transaction)
transaction.add_signature(signature)
previous_hash = blockchain.last_block["hash"]
block = Block(0, [transaction.to_json()], datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), previous_hash)
computed_hash = blockchain.proof_of_work(block)
self.assertGreater(len(computed_hash), 0)
def lightweight():
fullchain = [json.loads(block) for block in blockchain.chain]
lightweight = []
for block in fullchain:
block_object = Block(block['index'], block['transaction'], block['timestamp'], block['previous_hash'])
block_object.merkle_root = block['merkle_root']
block_object.nonce = block['nonce']
block_object.difficulty = block['difficulty']
lightweight.append(block_object.to_dict())
response = {
'chain': json.dumps(lightweight),
'length': len(lightweight)
}
return jsonify(response), 200
def mine(self, wallet: Wallet) -> Union[Block, bool]:
'''
method to generate new blocks and claim the block reward and all the transaction fees
It confirms all unconfirmed transactions into blocks by using the proof-of-work method.
convert to JSON to store transaction in the blockchain
'''
# get all available wallet addresses in the network
addresses = self.get_addresses_from_transactions()
# create Transaction objects for interest
interest_txs = self.create_interest_transactions(addresses)
for interest_tx in interest_txs:
self.unconfirmed_transactions.insert(0, interest_tx.to_json())
# add up all the transaction fee from all unconfirmed transactions
tx_fees = [
float(json.loads(transaction)['fee'])
for transaction in self.unconfirmed_transactions
]
total_tx_fee = sum(tx_fees)
# create and add a transaction into the list of unconfirmed transactions
# for sending out a block reward, which also include all of their transaction fees
block_reward = Transaction("Block_Reward", wallet.pubkey,
str(5.0 + total_tx_fee))
self.unconfirmed_transactions.insert(0, block_reward.to_json())
# if there are no unconfirmed transactions, return False
if not self.unconfirmed_transactions:
return False
new_block = Block(
index=self.last_block['index'] + 1,
transaction=self.unconfirmed_transactions,
timestamp=datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S"),
previous_hash=self.last_block['hash'])
new_block.difficulty = self.next_difficulty(self.last_block)
proof = self.proof_of_work(new_block)
if self.add_block(new_block, proof):
self.unconfirmed_transactions = []
return new_block
else:
return False
def valid_chain(self, chain: List[str]) -> bool:
'''check if a blockchain (all blocks) is valid'''
current_index = 0
chain = json.loads(chain)
# load and check every block from the blockchain
while current_index < len(chain):
block = json.loads(chain[current_index])
current_block = Block(block['index'], block['transaction'],
block['timestamp'], block['previous_hash'])
current_block.merkle_root = block['merkle_root']
current_block.nonce = block['nonce']
current_block.difficulty = block['difficulty']
# if the current block is NOT the last block
if current_index + 1 < len(chain):
# if the hash value of the current block != previous block's hash value of the next block, then reject
if current_block.compute_hash() != json.loads(
chain[current_index + 1])['previous_hash']:
return False
# check if the current block is an instance from the list of chain
if isinstance(current_block.transaction, list):
for transaction in current_block.transaction:
transaction = json.loads(transaction)
# Skip block reward because it does not have signature
if transaction['sender'] == 'Block_Reward':
continue
current_transaction = Transaction(transaction['sender'],
transaction['recipient'],
transaction['value'])
current_transaction.signature = transaction['signature']
# check if digital signature of each transaction is valid, if not then reject
if not current_transaction.verify_transaction_signature():
return False
# check if hash value of the current block is not valid, if yes then reject
if not self.is_valid_proof(current_block, block['hash']):
return False
current_index += 1
return True