def create_block():
with open(parentdir + "/core" + "/key.pem") as f:
key = RSA.importKey(f.read())
""" First transaction for first block """
trans1 = {
"vin": [None], # First transaction
"vout": [{
"amount": 1000000.0,
"address": key.publickey().exportKey().decode()
}]
}
trans1["txid"] = sha(json.dumps(trans1))
block1 = {
"header": {
"prev_block_hash": None,
"merkle_root": None,
"timestamp": None,
"nonce": None,
"difficulty_target": "0"
},
"transactions": [trans1]
}
utxo = UTXO()
blockdb = Blockdb()
blockdb.add_block(block1)
utxo.add_trans(block1['transactions'], sha(json.dumps(block1['header'])))
def req_block(self, conn):
"""
conn : socket object
the connection with the longest chain
Send the hash of the latest block all nodes will send back the
number of missing blocks, this node will extend using the longest chain
method
"""
latest = self.blockdb.get_latest()
conn.send("GET_BLOCKS".encode())
conn.send(str(latest).encode())
num_blocks = int(conn.recv(1024).decode())
block_num = 1
while block_num <= num_blocks:
block_size = int(conn.recv(1024).decode())
block = conn.recv(1024)
while len(block) < block_size:
block += conn.recv(1024)
block = json.loads(block.decode())
self.utxo.add_trans(block['transactions'], sha(json.dumps(block)))
self.blockdb.add_block(block) ## DOESNT VARIFY THE BLOCK
block_num += 1
print("Blockchain Updated")
def new_trans(self, amount, recepient):
"""
amount : float
the total payment to the recepient
recepient : str
the public key address of the receiving party
returns: json
a json data structure with input/output information of the transaction
"""
trans, change = self._get_unspent(amount)
vin = []
for t in trans:
sig = self.sign(t[1]) # sign transaction id
vin.append({
'txid': t[1], # (id, txid, address, change, amount, block)
'change': t[3], # boolean 0 or 1
'sig': sig,
})
vout = [{"amount": amount, "address": recepient}]
if change > 0:
vout.append({
"amount": change,
"address": self.key.publickey().exportKey().decode()
})
data = {"vin": vin, "vout": vout}
data['txid'] = sha(json.dumps(data)) # hashes the transaction
self.broadcast(data)
def add_block(self, block):
block_hash = sha(json.dumps(block['header']))
# check if block is already saved
get_block = self.get_block_by_hash(block_hash)
if get_block != None:
return None
block_num = self.get_latest()
if block_num == None:
block_num = 1
else:
block_num += 1
file = f"/block_{block_num}.json"
# save the block as a file
with open(parentdir + "/blocks" + file, "w") as f:
json.dump(block, f)
# add block to hash-table database
with self.conn:
self.c.execute("INSERT INTO blocks VALUES (NULL, :hash, :file)", {
'hash': block_hash,
'file': f'block_{block_num}.json'
})
def verify_pow(self, header):
diff = header["difficulty_target"]
hashed = sha(json.dumps(header))
if hashed[:len(diff)] == diff:
return True
else:
return False
def verify_prev_block(self, header):
block_num = self.get_block_num()
with open(self.path + f"/block_{block_num}.json") as f:
block = json.load(f)
hashed = sha(json.dumps(block['header']))
if hashed == header['prev_block_hash']:
return True
else:
return False
def merkle_root(self, leaves):
num_leaves = len(leaves)
if num_leaves == 1:
if type(leaves[0]) == dict: # For blocks with a single transaction
return sha(json.dumps(leaves[0]))
else:
return leaves[0]
parent = [ ]
i = 0
while i < num_leaves:
left = sha(json.dumps(leaves[i]))
if (i + 1) < num_leaves:
right = sha(json.dumps(leaves[i + 1]))
else:
right = sha(json.dumps(leaves[i]))
parent.append(sha(left + right))
i += 2
return self.merkle_root(parent)
def proof_of_work(self, merkle_root):
hashed = "1" * len(self.diff)
while hashed[:len(self.diff)] != self.diff:
header = {
"prev_block_hash": self.prev_block_hash,
"merkle_root": merkle_root,
"timestamp": str(datetime.datetime.now().isoformat()),
"nonce": str(random.getrandbits(32)),
"difficulty_target": self.diff
}
hashed = sha(json.dumps(header))
return header
def new_block(self, conn, block):
utxo = UTXO()
blockdb = Blockdb()
# check if block is already in the local chain
exists = blockdb.get_block_by_hash(sha(block))
if exists != None:
return None
# ensure the block is valid
if not self.verify("block", block):
return None
logging.debug("New block verified")
# remove all transaction in the block from unconfirmed pool
self.pool.check_new_block(sha(block))
# add all transaction outputs to utxo
utxo.add_trans(block['transactions'], sha(json.dumps(block)))
# remove all inputs from utxo
utxo.remove_trans(block['transactions'])
# save block in Blockdb
blockdb.add_block(block)
# propogate block
self.client.prop_block(json.dumps(block).encode())
def verify_hash(self, trans):
""" trans : dict
transaction data structure
returns : boolean
True if txid matches the hash of the transaction
"""
tcopy = trans.copy()
del tcopy['txid']
hashed = sha(json.dumps(tcopy))
if trans['txid'] == hashed:
return True
else:
return False
