def create_tx(current_owner, new_owner, tx_input, operation, payload=None):
"""Create a new transaction
A transaction in the bigchain is a transfer of a digital asset between two entities represented
by public keys.
Currently the bigchain supports two types of operations:
`CREATE` - Only federation nodes are allowed to use this operation. In a create operation
a federation node creates a digital asset in the bigchain and assigns that asset to a public
key. The owner of the private key can then decided to transfer this digital asset by using the
`transaction id` of the transaction as an input in a `TRANSFER` transaction.
`TRANSFER` - A transfer operation allows for a transfer of the digital assets between entities.
Args:
current_owner (str): base58 encoded public key of the current owner of the asset.
new_owner (str): base58 encoded public key of the new owner of the digital asset.
tx_input (str): id of the transaction to use as input.
operation (str): Either `CREATE` or `TRANSFER` operation.
payload (Optional[dict]): dictionary with information about asset.
Returns:
dict: unsigned transaction.
Raises:
TypeError: if the optional ``payload`` argument is not a ``dict``.
"""
data = None
if payload is not None:
if isinstance(payload, dict):
hash_payload = crypto.hash_data(serialize(payload))
data = {'hash': hash_payload, 'payload': payload}
else:
raise TypeError('`payload` must be an dict instance')
hash_payload = crypto.hash_data(serialize(payload))
data = {'hash': hash_payload, 'payload': payload}
tx = {
'current_owner': current_owner,
'new_owner': new_owner,
'input': tx_input,
'operation': operation,
'timestamp': timestamp(),
'data': data
}
# serialize and convert to bytes
tx_serialized = serialize(tx)
tx_hash = crypto.hash_data(tx_serialized)
# create the transaction
transaction = {'id': tx_hash, 'transaction': tx}
return transaction
def test_invalid_transactions_in_block(self, b, user_public_key, ):
# invalid transaction
valid_input = b.get_owned_ids(user_public_key).pop()
tx_invalid = b.create_transaction('a', 'b', valid_input, 'c')
block = b.create_block([tx_invalid])
# create a block with invalid transactions
block = {
'timestamp': util.timestamp(),
'transactions': [tx_invalid],
'node_pubkey': b.me,
'voters': b.federation_nodes
}
block_data = util.serialize(block)
block_hash = crypto.hash_data(block_data)
block_signature = crypto.SigningKey(b.me_private).sign(block_data)
block = {
'id': block_hash,
'block': block,
'signature': block_signature,
'votes': []
}
with pytest.raises(exceptions.TransactionOwnerError) as excinfo:
b.validate_block(block)
assert excinfo.value.args[0] == 'current_owner `a` does not own the input `{}`'.format(valid_input)
def create_block(self, validated_transactions):
"""Creates a block given a list of `validated_transactions`.
Note that this method does not validate the transactions. Transactions should be validated before
calling create_block.
Args:
validated_transactions (list): list of validated transactions.
Returns:
dict: created block.
"""
# Prevent the creation of empty blocks
if len(validated_transactions) == 0:
raise exceptions.OperationError("Empty block creation is not allowed")
# Create the new block
block = {
"timestamp": util.timestamp(),
"transactions": validated_transactions,
"node_pubkey": self.me,
"voters": self.nodes_except_me + [self.me],
}
# Calculate the hash of the new block
block_data = util.serialize(block)
block_hash = crypto.hash_data(block_data)
block_signature = crypto.SigningKey(self.me_private).sign(block_data)
block = {"id": block_hash, "block": block, "signature": block_signature}
return block
def test_invalid_transactions_in_block(self, b):
# invalid transaction
create_inputs()
valid_input = b.get_owned_ids(USER_PUBLIC_KEY).pop()
tx_invalid = b.create_transaction('a', 'b', valid_input, 'c')
block = b.create_block([tx_invalid])
assert invalid_transactions == [tx_invalid]
# create a block with invalid transactions
block = {
'timestamp': b.timestamp(),
'transactions': [tx_invalid],
'node_pubkey': b.me,
'voters': b.federation_nodes
}
block_data = b.serialize(block)
block_hash = hash_data(block_data)
block_signature = PrivateKey(b.me_private).sign(block_data)
block = {
'id': block_hash,
'block': block,
'signature': block_signature,
'votes': []
}
with pytest.raises(exceptions.TransactionOwnerError) as excinfo:
b.validate_block(block)
assert excinfo.value.args[0] == 'current_owner `a` does not own the input `{}`'.format(valid_input)
def validate_block(bigchain, block):
"""Validate a block.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
block (dict): block to validate.
Returns:
The block if the block is valid else it raises an exception
describing the reason why the block is invalid.
Raises:
InvalidHash: if the hash of the block is wrong.
"""
# Check if current hash is correct
calculated_hash = crypto.hash_data(util.serialize(block['block']))
if calculated_hash != block['id']:
raise exceptions.InvalidHash()
# Check if the block was created by a federation node
if block['block']['node_pubkey'] not in (bigchain.nodes_except_me +
[bigchain.me]):
raise exceptions.OperationError(
'Only federation nodes can create blocks')
# Check if block signature is valid
verifying_key = crypto.VerifyingKey(block['block']['node_pubkey'])
if not verifying_key.verify(util.serialize(block['block']),
block['signature']):
raise exceptions.InvalidSignature('Invalid block signature')
return block
def validate_block(bigchain, block):
"""Validate a block.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
block (dict): block to validate.
Returns:
The block if the block is valid else it raises an exception
describing the reason why the block is invalid.
Raises:
InvalidHash: if the hash of the block is wrong.
"""
# Check if current hash is correct
calculated_hash = crypto.hash_data(util.serialize(block['block']))
if calculated_hash != block['id']:
raise exceptions.InvalidHash()
# Check if the block was created by a federation node
if block['block']['node_pubkey'] not in (bigchain.federation_nodes + [bigchain.me]):
raise exceptions.OperationError('Only federation nodes can create blocks')
# Check if block signature is valid
verifying_key = crypto.VerifyingKey(block['block']['node_pubkey'])
if not verifying_key.verify(util.serialize(block['block']), block['signature']):
raise exceptions.InvalidSignature('Invalid block signature')
return block
def test_invalid_transactions_in_block(self, b, user_public_key, ):
# invalid transaction
valid_input = b.get_owned_ids(user_public_key).pop()
tx_invalid = b.create_transaction('a', 'b', valid_input, 'c')
block = b.create_block([tx_invalid])
assert invalid_transactions == [tx_invalid]
# create a block with invalid transactions
block = {
'timestamp': b.timestamp(),
'transactions': [tx_invalid],
'node_pubkey': b.me,
'voters': b.federation_nodes
}
block_data = b.serialize(block)
block_hash = hash_data(block_data)
block_signature = PrivateKey(b.me_private).sign(block_data)
block = {
'id': block_hash,
'block': block,
'signature': block_signature,
'votes': []
}
with pytest.raises(exceptions.TransactionOwnerError) as excinfo:
b.validate_block(block)
assert excinfo.value.args[0] == 'current_owner `a` does not own the input `{}`'.format(valid_input)
def exists(digital_asset_payload):
payload_hash = crypto.hash_data(util.serialize(digital_asset_payload))
transactions = b.get_tx_by_payload_hash(payload_hash)
result = transactions is not None and len(transactions) > 0
return result
def create_block(self, validated_transactions):
"""Creates a block given a list of `validated_transactions`.
Note that this method does not validate the transactions. Transactions should be validated before
calling create_block.
Args:
validated_transactions (list): list of validated transactions.
Returns:
dict: created block.
"""
# Create the new block
block = {
'timestamp': util.timestamp(),
'transactions': validated_transactions,
'node_pubkey': self.me,
'voters': self.federation_nodes + [self.me]
}
# Calculate the hash of the new block
block_data = util.serialize(block)
block_hash = crypto.hash_data(block_data)
block_signature = crypto.SigningKey(self.me_private).sign(block_data)
block = {
'id': block_hash,
'block': block,
'signature': block_signature,
'votes': []
}
return block
def exists(digital_asset_payload):
payload_hash = crypto.hash_data(util.serialize(digital_asset_payload))
transactions = b.get_tx_by_payload_hash(payload_hash)
result = transactions is not None and len(transactions) > 0
return result
def create_block(self, validated_transactions):
"""Creates a block given a list of `validated_transactions`.
Note that this method does not validate the transactions. Transactions should be validated before
calling create_block.
Args:
validated_transactions (list): list of validated transactions.
Returns:
dict: created block.
"""
# Create the new block
block = {
'timestamp': util.timestamp(),
'transactions': validated_transactions,
'node_pubkey': self.me,
'voters': self.federation_nodes + [self.me]
}
# Calculate the hash of the new block
block_data = util.serialize(block)
block_hash = crypto.hash_data(block_data)
block_signature = crypto.SigningKey(self.me_private).sign(block_data).decode()
block = {
'id': block_hash,
'block': block,
'signature': block_signature,
'votes': []
}
return block
def check_hash_and_signature(transaction):
# Check hash of the transaction
calculated_hash = crypto.hash_data(serialize(transaction['transaction']))
if calculated_hash != transaction['id']:
raise exceptions.InvalidHash()
# Check signature
if not verify_signature(transaction):
raise exceptions.InvalidSignature()
def test_create_new_block(self, b):
new_block = b.create_block([])
block_hash = hash_data(b.serialize(new_block['block']))
assert new_block['block']['voters'] == [b.me]
assert new_block['block']['node_pubkey'] == b.me
assert PublicKey(b.me).verify(b.serialize(new_block['block']), new_block['signature']) is True
assert new_block['id'] == block_hash
assert new_block['votes'] == []
def check_hash_and_signature(transaction):
# Check hash of the transaction
calculated_hash = hash_data(serialize(transaction['transaction']))
if calculated_hash != transaction['id']:
raise exceptions.InvalidHash()
# Check signature
if not verify_signature(transaction):
raise exceptions.InvalidSignature()
def test_create_new_block(self, b):
new_block = b.create_block([])
block_hash = hash_data(b.serialize(new_block['block']))
assert new_block['block']['voters'] == [b.me]
assert new_block['block']['node_pubkey'] == b.me
assert PublicKey(b.me).verify(b.serialize(new_block['block']), new_block['signature']) == True
assert new_block['id'] == block_hash
assert new_block['votes'] == []
def test_create_new_block(self, b):
new_block = b.create_block([])
block_hash = crypto.hash_data(util.serialize(new_block['block']))
assert new_block['block']['voters'] == [b.me]
assert new_block['block']['node_pubkey'] == b.me
assert crypto.VerifyingKey(b.me).verify(util.serialize(new_block['block']), new_block['signature']) is True
assert new_block['id'] == block_hash
assert new_block['votes'] == []
def test_transaction_hash(self, b):
payload = {'cats': 'are awesome'}
tx = b.create_transaction('a', 'b', 'c', 'd', payload)
tx_calculated = {
'current_owner': 'a',
'new_owner': 'b',
'input': 'c',
'operation': 'd',
'timestamp': tx['transaction']['timestamp'],
'data': {
'hash': hash_data(b.serialize(payload)),
'payload': payload
}
}
assert tx['transaction']['data'] == tx_calculated['data']
def test_transaction_hash(self, b):
payload = {'cats': 'are awesome'}
tx = b.create_transaction('a', 'b', 'c', 'd', payload)
tx_calculated = {
'current_owner': 'a',
'new_owner': 'b',
'input': 'c',
'operation': 'd',
'timestamp': tx['transaction']['timestamp'],
'data': {
'hash': hash_data(b.serialize(payload)),
'payload': payload
}
}
assert tx['transaction']['data'] == tx_calculated['data']
def get_hash_data(transaction):
""" Get the hashed data that (should) correspond to the `transaction['id']`
Args:
transaction (dict): the transaction to be hashed
Returns:
str: the hash of the transaction
"""
tx = copy.deepcopy(transaction)
if 'transaction' in tx:
tx = tx['transaction']
# remove the fulfillment messages (signatures)
for fulfillment in tx['fulfillments']:
fulfillment['fulfillment'] = None
return crypto.hash_data(serialize(tx))
def get_hash_data(transaction):
""" Get the hashed data that (should) correspond to the `transaction['id']`
Args:
transaction (dict): the transaction to be hashed
Returns:
str: the hash of the transaction
"""
tx = copy.deepcopy(transaction)
if 'transaction' in tx:
tx = tx['transaction']
# remove the fulfillment messages (signatures)
for fulfillment in tx['fulfillments']:
fulfillment['fulfillment'] = None
return crypto.hash_data(serialize(tx))
def validate_block(bigchain, block):
"""Validate a block.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
block (dict): block to validate.
Returns:
The block if the block is valid else it raises an exception
describing the reason why the block is invalid.
Raises:
InvalidHash: if the hash of the block is wrong.
"""
# Check if current hash is correct
calculated_hash = crypto.hash_data(util.serialize(block['block']))
if calculated_hash != block['id']:
raise exceptions.InvalidHash()
return block
def validate_block(bigchain, block):
"""Validate a block.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
block (dict): block to validate.
Returns:
The block if the block is valid else it raises an exception
describing the reason why the block is invalid.
Raises:
InvalidHash: if the hash of the block is wrong.
"""
# Check if current hash is correct
calculated_hash = crypto.hash_data(util.serialize(block['block']))
if calculated_hash != block['id']:
raise exceptions.InvalidHash()
return block
def create_block(self, validated_transactions):
"""Creates a block given a list of `validated_transactions`.
Note that this method does not validate the transactions. Transactions should be validated before
calling create_block.
Args:
validated_transactions (list): list of validated transactions.
Returns:
dict: created block.
"""
# Prevent the creation of empty blocks
if len(validated_transactions) == 0:
raise exceptions.OperationError(
'Empty block creation is not allowed')
# Create the new block
block = {
'timestamp': util.timestamp(),
'transactions': validated_transactions,
'node_pubkey': self.me,
'voters': self.nodes_except_me + [self.me]
}
# Calculate the hash of the new block
block_data = util.serialize(block)
block_hash = crypto.hash_data(block_data)
block_signature = crypto.SigningKey(self.me_private).sign(block_data)
block = {
'id': block_hash,
'block': block,
'signature': block_signature,
'votes': []
}
return block
def create_block(self, validated_transactions):
"""Creates a block given a list of `validated_transactions`.
Note that this method does not validate the transactions. Transactions should be validated before
calling create_block.
Args:
validated_transactions (list): list of validated transactions.
Returns:
dict: created block.
"""
# Prevent the creation of empty blocks
if len(validated_transactions) == 0:
raise exceptions.OperationError('Empty block creation is not allowed')
# Create the new block
block = {
'timestamp': util.timestamp(),
'transactions': validated_transactions,
'node_pubkey': self.me,
'voters': self.nodes_except_me + [self.me]
}
# Calculate the hash of the new block
block_data = util.serialize(block)
block_hash = crypto.hash_data(block_data)
block_signature = crypto.SigningKey(self.me_private).sign(block_data)
block = {
'id': block_hash,
'block': block,
'signature': block_signature,
'votes': []
}
return block
def validate_block(self, block):
"""Validate a block.
Args:
block (dict): block to validate.
Returns:
The block if the block is valid else it raises and exception
describing the reason why the block is invalid.
"""
# 1. Check if current hash is correct
calculated_hash = crypto.hash_data(util.serialize(block['block']))
if calculated_hash != block['id']:
raise exceptions.InvalidHash()
# 2. Validate all transactions in the block
for transaction in block['block']['transactions']:
if not self.is_valid_transaction(transaction):
# this will raise the exception
self.validate_transaction(transaction)
return block
def create_tx(current_owners, new_owners, inputs, operation, payload=None):
"""Create a new transaction
A transaction in the bigchain is a transfer of a digital asset between two entities represented
by public keys.
Currently the bigchain supports two types of operations:
`CREATE` - Only federation nodes are allowed to use this operation. In a create operation
a federation node creates a digital asset in the bigchain and assigns that asset to a public
key. The owner of the private key can then decided to transfer this digital asset by using the
`transaction id` of the transaction as an input in a `TRANSFER` transaction.
`TRANSFER` - A transfer operation allows for a transfer of the digital assets between entities.
Args:
current_owners (list): base58 encoded public key of the current owners of the asset.
new_owners (list): base58 encoded public key of the new owners of the digital asset.
inputs (list): id of the transaction to use as input.
operation (str): Either `CREATE` or `TRANSFER` operation.
payload (Optional[dict]): dictionary with information about asset.
Returns:
dict: unsigned transaction.
Raises:
TypeError: if the optional ``payload`` argument is not a ``dict``.
Reference:
{
"id": "<sha3 hash>",
"version": "transaction version number",
"transaction": {
"fulfillments": [
{
"current_owners": ["list of <pub-keys>"],
"input": {
"txid": "<sha3 hash>",
"cid": "condition index"
},
"fulfillment": "fulfillement of condition cid",
"fid": "fulfillment index"
}
],
"conditions": [
{
"new_owners": ["list of <pub-keys>"],
"condition": "condition to be met",
"cid": "condition index (1-to-1 mapping with fid)"
}
],
"operation": "<string>",
"timestamp": "<timestamp from client>",
"data": {
"hash": "<SHA3-256 hash hexdigest of payload>",
"payload": {
"title": "The Winds of Plast",
"creator": "Johnathan Plunkett",
"IPFS_key": "QmfQ5QAjvg4GtA3wg3adpnDJug8ktA1BxurVqBD8rtgVjP"
}
}
},
}
"""
# validate arguments (owners and inputs should be lists or None)
# The None case appears on fulfilling a hashlock
if current_owners is None:
current_owners = []
if not isinstance(current_owners, list):
current_owners = [current_owners]
# The None case appears on assigning a hashlock
if new_owners is None:
new_owners = []
if not isinstance(new_owners, list):
new_owners = [new_owners]
if not isinstance(inputs, list):
inputs = [inputs]
# handle payload
data = None
if payload is not None:
if isinstance(payload, dict):
hash_payload = crypto.hash_data(serialize(payload))
data = {'hash': hash_payload, 'payload': payload}
else:
raise TypeError('`payload` must be an dict instance')
# handle inputs
fulfillments = []
# transfer
if inputs:
for fid, tx_input in enumerate(inputs):
fulfillments.append({
'current_owners': current_owners,
'input': tx_input,
'fulfillment': None,
'fid': fid
})
# create
else:
fulfillments.append({
'current_owners': current_owners,
'input': None,
'fulfillment': None,
'fid': 0
})
# handle outputs
conditions = []
for fulfillment in fulfillments:
# threshold condition
if len(new_owners) > 1:
condition = cc.ThresholdSha256Fulfillment(
threshold=len(new_owners))
for new_owner in new_owners:
condition.add_subfulfillment(
cc.Ed25519Fulfillment(public_key=new_owner))
# simple signature condition
elif len(new_owners) == 1:
condition = cc.Ed25519Fulfillment(public_key=new_owners[0])
# to be added later (hashlock conditions)
else:
condition = None
if condition:
conditions.append({
'new_owners': new_owners,
'condition': {
'details': rapidjson.loads(condition.serialize_json()),
'uri': condition.condition_uri
},
'cid': fulfillment['fid']
})
tx = {
'fulfillments': fulfillments,
'conditions': conditions,
'operation': operation,
'timestamp': timestamp(),
'data': data
}
# serialize and convert to bytes
tx_hash = get_hash_data(tx)
# create the transaction
transaction = {'id': tx_hash, 'version': 1, 'transaction': tx}
return transaction
def create_tx(current_owners, new_owners, inputs, operation, payload=None):
"""Create a new transaction
A transaction in the bigchain is a transfer of a digital asset between two entities represented
by public keys.
Currently the bigchain supports two types of operations:
`CREATE` - Only federation nodes are allowed to use this operation. In a create operation
a federation node creates a digital asset in the bigchain and assigns that asset to a public
key. The owner of the private key can then decided to transfer this digital asset by using the
`transaction id` of the transaction as an input in a `TRANSFER` transaction.
`TRANSFER` - A transfer operation allows for a transfer of the digital assets between entities.
Args:
current_owners (list): base58 encoded public key of the current owners of the asset.
new_owners (list): base58 encoded public key of the new owners of the digital asset.
inputs (list): id of the transaction to use as input.
operation (str): Either `CREATE` or `TRANSFER` operation.
payload (Optional[dict]): dictionary with information about asset.
Returns:
dict: unsigned transaction.
Raises:
TypeError: if the optional ``payload`` argument is not a ``dict``.
Reference:
{
"id": "<sha3 hash>",
"version": "transaction version number",
"transaction": {
"fulfillments": [
{
"current_owners": ["list of <pub-keys>"],
"input": {
"txid": "<sha3 hash>",
"cid": "condition index"
},
"fulfillment": "fulfillement of condition cid",
"fid": "fulfillment index"
}
],
"conditions": [
{
"new_owners": ["list of <pub-keys>"],
"condition": "condition to be met",
"cid": "condition index (1-to-1 mapping with fid)"
}
],
"operation": "<string>",
"timestamp": "<timestamp from client>",
"data": {
"hash": "<SHA3-256 hash hexdigest of payload>",
"payload": {
"title": "The Winds of Plast",
"creator": "Johnathan Plunkett",
"IPFS_key": "QmfQ5QAjvg4GtA3wg3adpnDJug8ktA1BxurVqBD8rtgVjP"
}
}
},
}
"""
# validate arguments (owners and inputs should be lists or None)
# The None case appears on fulfilling a hashlock
if current_owners is None:
current_owners = []
if not isinstance(current_owners, list):
current_owners = [current_owners]
# The None case appears on assigning a hashlock
if new_owners is None:
new_owners = []
if not isinstance(new_owners, list):
new_owners = [new_owners]
if not isinstance(inputs, list):
inputs = [inputs]
# handle payload
data = None
if payload is not None:
if isinstance(payload, dict):
hash_payload = crypto.hash_data(serialize(payload))
data = {
'hash': hash_payload,
'payload': payload
}
else:
raise TypeError('`payload` must be an dict instance')
# handle inputs
fulfillments = []
# transfer
if inputs:
for fid, tx_input in enumerate(inputs):
fulfillments.append({
'current_owners': current_owners,
'input': tx_input,
'fulfillment': None,
'fid': fid
})
# create
else:
fulfillments.append({
'current_owners': current_owners,
'input': None,
'fulfillment': None,
'fid': 0
})
# handle outputs
conditions = []
for fulfillment in fulfillments:
# threshold condition
if len(new_owners) > 1:
condition = cc.ThresholdSha256Fulfillment(threshold=len(new_owners))
for new_owner in new_owners:
condition.add_subfulfillment(cc.Ed25519Fulfillment(public_key=new_owner))
# simple signature condition
elif len(new_owners) == 1:
condition = cc.Ed25519Fulfillment(public_key=new_owners[0])
# to be added later (hashlock conditions)
else:
condition = None
if condition:
conditions.append({
'new_owners': new_owners,
'condition': {
'details': json.loads(condition.serialize_json()),
'uri': condition.condition.serialize_uri()
},
'cid': fulfillment['fid']
})
tx = {
'fulfillments': fulfillments,
'conditions': conditions,
'operation': operation,
'timestamp': timestamp(),
'data': data
}
# serialize and convert to bytes
tx_hash = get_hash_data(tx)
# create the transaction
transaction = {
'id': tx_hash,
'version': 1,
'transaction': tx
}
return transaction
def validate_transaction(bigchain, transaction):
"""Validate a transaction.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
transaction (dict): transaction to validate.
Returns:
The transaction if the transaction is valid else it raises an
exception describing the reason why the transaction is invalid.
Raises:
OperationError: if the transaction operation is not supported
TransactionDoesNotExist: if the input of the transaction is not found
TransactionOwnerError: if the new transaction is using an input it doesn't own
DoubleSpend: if the transaction is a double spend
InvalidHash: if the hash of the transaction is wrong
InvalidSignature: if the signature of the transaction is wrong
"""
# If the operation is CREATE the transaction should have no inputs and
# should be signed by a federation node
if transaction['transaction']['operation'] == 'CREATE':
if transaction['transaction']['input']:
raise ValueError('A CREATE operation has no inputs')
if transaction['transaction']['current_owner'] not in (
bigchain.federation_nodes + [bigchain.me]):
raise exceptions.OperationError(
'Only federation nodes can use the operation `CREATE`')
else:
# check if the input exists, is owned by the current_owner
if not transaction['transaction']['input']:
raise ValueError(
'Only `CREATE` transactions can have null inputs')
tx_input = bigchain.get_transaction(
transaction['transaction']['input'])
if not tx_input:
raise exceptions.TransactionDoesNotExist(
'input `{}` does not exist in the bigchain'.format(
transaction['transaction']['input']))
if (tx_input['transaction']['new_owner'] !=
transaction['transaction']['current_owner']):
raise exceptions.TransactionOwnerError(
'current_owner `{}` does not own the input `{}`'.format(
transaction['transaction']['current_owner'],
transaction['transaction']['input']))
# check if the input was already spent by a transaction other than
# this one.
spent = bigchain.get_spent(tx_input['id'])
if spent and spent['id'] != transaction['id']:
raise exceptions.DoubleSpend(
'input `{}` was already spent'.format(
transaction['transaction']['input']))
# Check hash of the transaction
calculated_hash = crypto.hash_data(
util.serialize(transaction['transaction']))
if calculated_hash != transaction['id']:
raise exceptions.InvalidHash()
# Check signature
if not util.verify_signature(transaction):
raise exceptions.InvalidSignature()
return transaction
def validate_transaction(bigchain, transaction):
"""Validate a transaction.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
transaction (dict): transaction to validate.
Returns:
The transaction if the transaction is valid else it raises an
exception describing the reason why the transaction is invalid.
Raises:
OperationError: if the transaction operation is not supported
TransactionDoesNotExist: if the input of the transaction is not found
TransactionOwnerError: if the new transaction is using an input it doesn't own
DoubleSpend: if the transaction is a double spend
InvalidHash: if the hash of the transaction is wrong
InvalidSignature: if the signature of the transaction is wrong
"""
# If the operation is CREATE the transaction should have no inputs and
# should be signed by a federation node
if transaction['transaction']['operation'] == 'CREATE':
if transaction['transaction']['input']:
raise ValueError('A CREATE operation has no inputs')
if transaction['transaction']['current_owner'] not in (
bigchain.federation_nodes + [bigchain.me]):
raise exceptions.OperationError(
'Only federation nodes can use the operation `CREATE`')
else:
# check if the input exists, is owned by the current_owner
if not transaction['transaction']['input']:
raise ValueError(
'Only `CREATE` transactions can have null inputs')
tx_input = bigchain.get_transaction(
transaction['transaction']['input'])
if not tx_input:
raise exceptions.TransactionDoesNotExist(
'input `{}` does not exist in the bigchain'.format(
transaction['transaction']['input']))
if (tx_input['transaction']['new_owner'] !=
transaction['transaction']['current_owner']):
raise exceptions.TransactionOwnerError(
'current_owner `{}` does not own the input `{}`'.format(
transaction['transaction']['current_owner'],
transaction['transaction']['input']))
# check if the input was already spent by a transaction other than
# this one.
spent = bigchain.get_spent(tx_input['id'])
if spent and spent['id'] != transaction['id']:
raise exceptions.DoubleSpend(
'input `{}` was already spent'.format(
transaction['transaction']['input']))
# Check hash of the transaction
calculated_hash = crypto.hash_data(util.serialize(
transaction['transaction']))
if calculated_hash != transaction['id']:
raise exceptions.InvalidHash()
# Check signature
if not util.verify_signature(transaction):
raise exceptions.InvalidSignature()
return transaction
def create_tx(current_owner, new_owner, tx_input, operation, payload=None):
"""Create a new transaction
A transaction in the bigchain is a transfer of a digital asset between two entities represented
by public keys.
Currently the bigchain supports two types of operations:
`CREATE` - Only federation nodes are allowed to use this operation. In a create operation
a federation node creates a digital asset in the bigchain and assigns that asset to a public
key. The owner of the private key can then decided to transfer this digital asset by using the
`transaction id` of the transaction as an input in a `TRANSFER` transaction.
`TRANSFER` - A transfer operation allows for a transfer of the digital assets between entities.
Args:
current_owner (str): base58 encoded public key of the current owner of the asset.
new_owner (str): base58 encoded public key of the new owner of the digital asset.
tx_input (str): id of the transaction to use as input.
operation (str): Either `CREATE` or `TRANSFER` operation.
payload (Optional[dict]): dictionary with information about asset.
Returns:
dict: unsigned transaction.
Raises:
TypeError: if the optional ``payload`` argument is not a ``dict``.
"""
data = None
if payload is not None:
if isinstance(payload, dict):
hash_payload = crypto.hash_data(serialize(payload))
data = {
'hash': hash_payload,
'payload': payload
}
else:
raise TypeError('`payload` must be an dict instance')
hash_payload = crypto.hash_data(serialize(payload))
data = {
'hash': hash_payload,
'payload': payload
}
tx = {
'current_owner': current_owner,
'new_owner': new_owner,
'input': tx_input,
'operation': operation,
'timestamp': timestamp(),
'data': data
}
# serialize and convert to bytes
tx_serialized = serialize(tx)
tx_hash = crypto.hash_data(tx_serialized)
# create the transaction
transaction = {
'id': tx_hash,
'transaction': tx
}
return transaction