资产创建

from bigchaindb_driver import BigchainDB
from bigchaindb_driver.crypto import generate_keypair

bdb_root_url = 'https://example.com:9984'  # Use YOUR BigchainDB Root URL here
bdb = BigchainDB(bdb_root_url)

alice = generate_keypair()

digital_asset_payload = {'data': {'msg': 'Hello BigchainDB!'}}
tx = bdb.transactions.prepare(operation='CREATE',
                          signers=alice.public_key,
                          asset=digital_asset_payload)

signed_tx = bdb.transactions.fulfill(tx, private_keys=alice.private_key)
sent_tx = bdb.transactions.send(signed_tx)
sent_tx == signed_tx

读取创建的事务

# Retrieve a block height
block_height = bdb.blocks.get(txid=signed_tx['id'])

# Retrieve a block
block = bdb.blocks.retrieve(block_height)

转移数字资产

为了准备一个转账事务，Alice需要提供至少三样东西:

1. inputs - 一个或多个实现先前事务的输出条件的实现
2. asset['id'] - 被转移的资产的id
3. 接收者的public_keys - 一个或多个表示新接收方的公钥。

创建input

output_index = 0

output = signed_tx['outputs'][output_index]

input_ = {
    'fulfillment': output['condition']['details'],
    'fulfills': {
        'output_index': output_index,
        'transaction_id': signed_tx['id'],
    },
    'owners_before': output['public_keys'],
}

转账事务中的资产必须是带有id键的字典:

transfer_asset_id = signed_tx['id']
transfer_asset = {
    'id': transfer_asset_id,
}

准备转移事务

tx_transfer = bdb.transactions.prepare(
    operation='TRANSFER',
    inputs=input_,
    asset=transfer_asset,
    recipients=bob.public_key,
)

交易现在需要由alice来完成:

signed_tx_transfer = bdb.transactions.fulfill(
    tx_transfer,
    private_keys=alice.private_key,
)

sent_tx_transfer = bdb.transactions.send(signed_tx_transfer)

Double Spends
相同的数字资产多次交易

from bigchaindb_driver.exceptions import BigchaindbException
try:
    bdb.transactions.send(fulfilled_tx_transfer_2)
except BigchaindbException as e:
    print(e.info)

# {'message': 'Invalid transaction', 'status': 400}

Multiple Owners
多个所有者

car_creation_tx = bdb.transactions.prepare(
    operation='CREATE',
    signers=alice.public_key,
    recipients=(alice.public_key, bob.public_key),
    asset=car_asset,
)

signed_car_creation_tx = bdb.transactions.fulfill(
    car_creation_tx,
    private_keys=alice.private_key,
)

或

signed_car_creation_tx = bdb.transactions.fulfill(
    car_creation_tx,
    private_keys=[alice.private_key, bob.private_key],
)

输出条件的目的是锁定交易，这样就需要一个有效的输入实现来解锁它。
在基于签名的方案中，锁基本上是一个公钥，这样为了解锁事务，就需要有私钥。