def load_data(self):
"""Initialize blockchain + open transactions data from a file."""
session = Session()
blockchain_objects = session.query(Block).all()
blockchain = self.make_sendable_list(blockchain_objects)
all_mined_transactions_objects = session.query(Transaction)\
.filter(Transaction.mined == 1).all()
all_mined_transactions = self.make_sendable_list(all_mined_transactions_objects)
session.close()
self.chain = blockchain
self.mined_transactions = all_mined_transactions
if len(blockchain) == 0:
# Our starting block for the blockchain
session = Session()
genesis_block = Block(0, 'GENESIS', 'GENESIS', 100, -1)
session.add(genesis_block)
session.commit()
self.chain = session.query(Block).all()
session.close()
session = Session()
open_transactions_objects = session.query(Transaction)\
.filter(Transaction.mined == 0).all()
open_transactions = self.make_sendable_list(open_transactions_objects)
self.__open_transactions = open_transactions
peer_nodes_objects = session.query(Node).all()
peer_nodes = self.make_sendable_list(peer_nodes_objects)
self.__peer_nodes = peer_nodes
session.close()
def save_keys(self):
"""Saves the keys to a file (wallet.txt)."""
if self.public_key is not None and self.private_key is not None:
try:
with open('wallet-{}.txt'.format(self.node_id), mode='w') as f:
f.write(self.private_key)
session = Session()
wallet = Wallet(node_id=self.node_id,
public_key=self.public_key)
session.add(wallet)
session.commit()
session.close()
return True
except (IOError, IndexError):
print('Saving wallet failed...')
return False
def add_peer_node(self, node):
"""Adds a new node to the peer node set.
Arguments:
:node: The node URL which should be added.
"""
session = Session()
new_peer_node = Node(node)
session.add(new_peer_node)
try:
session.commit()
except IntegrityError:
return False
session.close()
self.load_data()
return True
def remove_peer_node(self, node):
"""Removes a node from the peer node set.
Arguments:
:node: The node URL which should be removed.
"""
session = Session()
obj = session.query(Node).filter(text("id == :node_id"))\
.params(node_id=node).one()
session.delete(obj)
try:
session.commit()
except NoResultFound:
return False
session.close()
self.load_data()
return True
def add_transaction(self,
recipient,
sender,
signature,
amount=1.0,
time=0,
is_receiving=False):
""" Append a new value as well as the last blockchain value to the blockchain.
Arguments:
:sender: The sender of the coins.
:recipient: The recipient of the coins.
:signature: The signature of the transaction.
:amount: The amount of coins sent with the transaction
:time: The time when the transaction was made (generated with time())
(default = 1.0)
"""
session = Session()
transaction = Transaction(sender, recipient, signature, amount, timed=time)
session.add(transaction)
if Verification.verify_transaction(transaction, self.get_balance):
session.commit()
session.close()
self.load_data()
if not is_receiving:
for node in self.__peer_nodes:
url = 'http://{}/broadcast-transaction'.format(node['id'])
try:
response = requests.post(url,
json={
'sender': sender,
'recipient': recipient,
'amount': amount,
'signature': signature,
'time': time
})
if (response.status_code == 400 or
response.status_code == 500):
print('Transaction declined, needs resolving')
return False
except requests.exceptions.ConnectionError:
continue
return True
return False
def resolve(self):
"""Checks all peer nodes' blockchains and replaces the local one with
longer valid ones."""
# Initialize the winner chain with the local chain
winner_chain = self.chain
winning_node = self.node_id
replace = False
for node in self.__peer_nodes:
url = 'http://{}/chain'.format(node['id'])
try:
# Send a request and store the response
response = requests.get(url)
# Retrieve the JSON data as a dictionary
peer_node_data = response.json()
node_chain = peer_node_data['chain']
# Convert the dictionary list to a list of block AND
# transaction objects
node_chain = [
Block(
block['index'],
block['previous_hash'],
block['hash_of_txs'],
block['proof'],
block['timestamp']) for block in node_chain
]
node_chain_length = len(node_chain)
local_chain_length = len(winner_chain)
# Store the received chain as the current winner chain if it's
# longer AND valid
if (node_chain_length > local_chain_length and
Verification.verify_chain(node_chain)):
winner_chain = node_chain
winning_node = node['id']
replace = True
except requests.exceptions.ConnectionError:
continue
self.resolve_conflicts = False
# Replace the local chain with the winner chain
if self.chain is not winner_chain and replace:
# get transactions from winning chain to replace the local ones
url = 'http://{}/gettransactions'.format(winning_node)
response = requests.get(url)
transactions_object = response.json()
transactions = transactions_object['transactions']
session = Session()
# delete local content of databases
session.query(Transaction).delete()
session.query(Block).delete()
try:
session.commit()
except NoResultFound as e:
print(e)
new_transactions = [
Transaction(
tx['sender'],
tx['recipient'],
tx['signature'],
tx['amount'],
tx['mined'],
tx['block'],
tx['time']) for tx in transactions
]
session.add_all(new_transactions)
session.add_all(winner_chain)
session.commit()
self.load_data()
return replace
def add_block(self, block, list_of_transactions):
"""Add a block which was received via broadcasting to the local
blockchain."""
# Validate the proof of work of the block and store the result (True
# or False) in a variable
proof_is_valid = Verification.valid_proof(
block['hash_of_txs'], block['previous_hash'], block['proof'])
# Check if previous_hash stored in the block is equal to the local
# blockchain's last block's hash and store the result in a block
last_block = self.__chain[-1]
index_of_block = block['index']
hashes_match = hash_block(last_block) == block['previous_hash']
if not proof_is_valid or not hashes_match:
return False
# Create a Block object
session = Session()
converted_block = Block(
index_of_block,
block['previous_hash'],
block['hash_of_txs'],
block['proof'],
block['timestamp'])
session.add(converted_block)
# create a Transaction object of the given mining reward transactions
# since this Transaction is not broadcasted
reward_transaction = list_of_transactions[-1]
reward_tx = Transaction(
reward_transaction['sender'],
reward_transaction['recipient'],
reward_transaction['signature'],
reward_transaction['amount'],
1, index_of_block,
reward_transaction['time'])
session.add(reward_tx)
session.commit()
session.close()
self.load_data()
# Check which open transactions were included in the received block
# and update the mined and block columns (except for the last transaction
# in the list, that is the mining reward)
mined_transactions = []
session = Session()
for itx in list_of_transactions[:-1]:
try:
for opentx in session.query(Transaction).filter(text("signature = :sign"))\
.params(sign=itx['signature']).all():
mined_transactions.append(opentx)
except NoResultFound:
continue
for tx in mined_transactions:
tx.block = index_of_block
tx.mined = 1
session.commit()
session.close()
self.load_data()
return True
def mine_block(self):
"""Create a new block and add open transactions to it."""
# Fetch the currently last block of the blockchain
if self.public_key is None:
return None
last_block = self.__chain[-1]
# Hash the last block (=> to be able to compare it to the stored hash
# value)
block_index = int(len(self.__chain))
print(block_index)
self.load_data()
reward_transaction = Transaction(
'MINING', str(self.public_key),
'REWARD FOR MINING BLOCK {}'.format(block_index),
MINING_REWARD, 1, block_index, time())
print("rwd tx: ", reward_transaction.block)
# Copy transaction instead of manipulating the original
# open_transactions list
# This ensures that if for some reason the mining should fail,
# we don't have the reward transaction stored in the open transactions
copied_transactions = self.__open_transactions[:]
for tx in copied_transactions:
if not Wallet.verify_transaction(tx):
return None
copied_transactions.append(reward_transaction)
# add and modify the objects in the database
hashed_transactions = Transaction.to_merkle_tree(copied_transactions)
hashed_block = hash_block(last_block)
proof = self.proof_of_work(hashed_transactions)
session = Session()
block = Block(block_index, hashed_block,
hashed_transactions, proof)
session.add(block)
session.add(reward_transaction)
session.commit()
open_txs = session.query(Transaction).filter(Transaction.mined == 0).all()
for tx in open_txs:
tx.block = block_index
tx.mined = 1
session.commit()
session.close()
self.load_data()
session = Session()
converted_block = session.query(Block)\
.filter(Block.index == block_index).one()
mined_transactions = session.query(Transaction).\
filter(Transaction.block == block_index).all()
session.close()
sendable_tx = self.make_sendable_list(mined_transactions)
dict_block = converted_block.__dict__.copy()
del dict_block['_sa_instance_state']
for node in self.__peer_nodes:
url = 'http://{}/broadcast-block'.format(node['id'])
try:
response = requests.post(url, json={'block': dict_block,
'transactions': sendable_tx})
if response.status_code == 400 or response.status_code == 500:
print('Block declined, needs resolving')
if response.status_code == 409:
self.resolve_conflicts = True
except requests.exceptions.ConnectionError:
continue
return block