added get_hash_data()

bigchaindb/consensus.py

@@ -153,12 +153,7 @@ class BaseConsensusRules(AbstractConsensusRules):
                         'input `{}` was already spent'.format(fulfillment['input']))
 
         # Check hash of the transaction
-        # remove the fulfillment messages (signatures)
-        transaction_data = copy.deepcopy(transaction)
-        for fulfillment in transaction_data['transaction']['fulfillments']:
-            fulfillment['fulfillment'] = None
-
-        calculated_hash = crypto.hash_data(util.serialize(transaction_data['transaction']))
+        calculated_hash = util.get_hash_data(transaction)
         if calculated_hash != transaction['id']:
             raise exceptions.InvalidHash()
 

bigchaindb/util.py

@@ -217,8 +217,7 @@ def create_tx(current_owners, new_owners, inputs, operation, payload=None):
     }
 
     # serialize and convert to bytes
-    tx_serialized = serialize(tx)
-    tx_hash = crypto.hash_data(tx_serialized)
+    tx_hash = get_hash_data(tx)
 
     # create the transaction
     transaction = {
@@ -268,7 +267,7 @@ def create_and_sign_tx(private_key, current_owner, new_owner, tx_input, operatio
 
 def check_hash_and_signature(transaction):
     # Check hash of the transaction
-    calculated_hash = crypto.hash_data(serialize(transaction['transaction']))
+    calculated_hash = get_hash_data(transaction)
     if calculated_hash != transaction['id']:
         raise exceptions.InvalidHash()
 
@@ -331,10 +330,22 @@ def get_fulfillment_message(transaction, fulfillment):
         # get previous condition
         previous_tx = b.get_transaction(fulfillment['input']['txid'])
         conditions = sorted(previous_tx['transaction']['conditions'], key=lambda d: d['cid'])
-        fulfillment_message['condition'] = conditions[fulfillment['fid']]
+        fulfillment_message['condition'] = conditions[fulfillment['input']['cid']]
     return fulfillment_message
 
 
+def get_hash_data(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 transform_create(tx):
     """Change the owner and signature for a ``CREATE`` transaction created by a node"""
 

docs/source/python-server-api-examples.md

@@ -114,11 +114,15 @@ tx_retrieved = b.get_transaction(tx_signed['id'])
 
 ```
 
-The new owner of the digital asset is now `ACJyBLfeLNpCPrGWYoPYvnQ2MAC8BFukBko4hxtW9YoH`, which is the public key of `testuser1`.
+The new owner of the digital asset is now `DTJCqP3sNkZcpoSA8bCtGwZ4ASfRLsMFXZDCmMHzCoeJ`, which is the public key of `testuser1`.
+
+Note that the current owner with public key `3LQ5dTiddXymDhNzETB1rEkp4mA7fEV1Qeiu5ghHiJm9` refers to one of the federation nodes that actually created the asset and assigned it to `testuser1`.
 
 ## Transfer the Digital Asset
 
-Now that `testuser1` has a digital asset assigned to him, he can transfer it to another user. Transfer transactions require an input. The input will be the transaction id of a digital asset that was assigned to `testuser1`, which in our case is `6539dded9479c47b3c83385ae569ecaa90bcf387240d1ee2ea3ae0f7986aeddd`.
+Now that `testuser1` has a digital asset assigned to him, he can transfer it to another user. Transfer transactions require an input. The input will be the transaction id of a digital asset that was assigned to `testuser1`, which in our case is `cdb6331f26ecec0ee7e67e4d5dcd63734e7f75bbd1ebe40699fc6d2960ae4cb2`.
+
+Since a transaction can have multiple outputs with each their own (crypto)condition, each transaction input should also refer to the condition index `cid`.
 
 ```python
 # create a second testuser
@@ -203,13 +207,29 @@ b.validate_transaction(tx_transfer_signed2)
 DoubleSpend: input `cdb6331f26ecec0ee7e67e4d5dcd63734e7f75bbd1ebe40699fc6d2960ae4cb2` was already spent
 ```
 
-## Crypto Conditions
+## Crypto-Conditions
+
+BigchainDB makes use of the crypto-conditions library to both cryptographically lock and unlock transactions.
+The locking script is refered to as a `condition` and a corresponding `fulfillment` unlocks the condition of the `input_tx`. 
+
+![BigchainDB transactions connecting fulfillments with conditions](./_static/tx_single_condition_single_fulfillment_v1.png)
+
 
 ### Introduction
 
+Crypto-conditions provide a mechanism to describe a signed message such that multiple actors in a distributed system can all verify the same signed message and agree on whether it matches the description. 
+
+This provides a useful primitive for event-based systems that are distributed on the Internet since we can describe events in a standard deterministic manner (represented by signed messages) and therefore define generic authenticated event handlers.
+
+Crypto-conditions are part of the Interledger protocol and the full specification can be found [here](https://interledger.org/five-bells-condition/spec.html).
+
+Implementations of the crypto-conditions are available in [Python](https://github.com/bigchaindb/cryptoconditions) and [JavaScript](https://github.com/interledger/five-bells-condition).
+
 
 ### Threshold Signatures
 
+MultiSig, m-of-n signatures
+
 ```python
 import copy
 import json

tests/db/test_bigchain_api.py

@@ -940,14 +940,8 @@ class TestCryptoconditions(object):
             'details': json.loads(first_tx_condition.serialize_json()),
             'uri': first_tx_condition.condition.serialize_uri()
         }
-
         # conditions have been updated, so hash needs updating
-        transaction_data = copy.deepcopy(first_tx)
-        for fulfillment in transaction_data['transaction']['fulfillments']:
-            fulfillment['fulfillment'] = None
-
-        calculated_hash = crypto.hash_data(util.serialize(transaction_data['transaction']))
-        first_tx['id'] = calculated_hash
+        first_tx['id'] = util.get_hash_data(first_tx)
 
         first_tx_signed = b.sign_transaction(first_tx, user_sk)
 
@@ -994,14 +988,8 @@ class TestCryptoconditions(object):
             'details': json.loads(first_tx_condition.serialize_json()),
             'uri': first_tx_condition.condition.serialize_uri()
         }
-
         # conditions have been updated, so hash needs updating
-        transaction_data = copy.deepcopy(first_tx)
-        for fulfillment in transaction_data['transaction']['fulfillments']:
-            fulfillment['fulfillment'] = None
-
-        calculated_hash = crypto.hash_data(util.serialize(transaction_data['transaction']))
-        first_tx['id'] = calculated_hash
+        first_tx['id'] = util.get_hash_data(first_tx)
 
         first_tx_signed = b.sign_transaction(first_tx, user_sk)