mirror of
https://github.com/bigchaindb/js-bigchaindb-driver.git
synced 2024-10-31 23:45:22 +01:00
88 lines
3.5 KiB
ReStructuredText
88 lines
3.5 KiB
ReStructuredText
|
|
.. Copyright BigchainDB GmbH and BigchainDB contributors
|
|
SPDX-License-Identifier: (Apache-2.0 AND CC-BY-4.0)
|
|
Code is Apache-2.0 and docs are CC-BY-4.0
|
|
|
|
=================
|
|
Advanced Examples
|
|
=================
|
|
|
|
Crypto Conditions
|
|
-----------------
|
|
|
|
Let's start with a basic use case example. Alice bought a bicycle for €240.
|
|
She will use the bike for a year and will give it to her daughter afterwards.
|
|
First, we create an asset registering the bicycle:
|
|
|
|
.. code-block:: js
|
|
|
|
const txCreateAliceSimple = driver.Transaction.makeCreateTransaction(
|
|
{'asset': 'bicycle'},
|
|
{'purchase_price': '€240'},
|
|
[
|
|
driver.Transaction.makeOutput(driver.Transaction.makeEd25519Condition(alice.publicKey))
|
|
],
|
|
alice.publicKey
|
|
)
|
|
|
|
const txCreateAliceSimpleSigned = driver.Transaction.signTransaction(txCreateAliceSimple, alice.privateKey)
|
|
|
|
After a year, she decides it's time to transfer the bicycle to her daughter Carly.
|
|
However, Alice wants to maintain the right over the bike so she can possibly sell it. If she would transfer the bicycle to Carly, she won't be able to do this.
|
|
So, Alice needs a crypto conditions that defines that she or her daughter can sign the ``TRANSFER`` transaction to a possible buyer.
|
|
|
|
We need to define a threshold as well. This defines how many persons have to sign the transaction to ``TRANSFER`` it.
|
|
In this case, we define two subconditions with the public keys from Alice and Carly. Next, we set the threshold to **one**.
|
|
This means that just one of the subconditions has to sign the transaction to transfer it.
|
|
This can be the mother Alice, or Carly herself.
|
|
|
|
.. code-block:: js
|
|
|
|
// Create condition for Alice and Carly
|
|
let subConditionFrom = driver.Transaction.makeEd25519Condition(alice.publicKey, false)
|
|
let subConditionTo = driver.Transaction.makeEd25519Condition(carly.publicKey, false)
|
|
|
|
// Create condition object with threshold and subconditions
|
|
let condition = driver.Transaction.makeThresholdCondition(1, [subConditionFrom, subConditionTo])
|
|
|
|
// Generate output with condition added
|
|
let output = driver.Transaction.makeOutput(condition)
|
|
|
|
// Add Carly to the output.public_keys field so she is the owner
|
|
output.public_keys = [carly.publicKey]
|
|
|
|
let transaction = driver.Transaction.makeTransferTransaction(
|
|
[{ tx: txCreateAliceSimpleSigned, output_index: 0 }],
|
|
[output],
|
|
{'meta': 'Transfer to new user with conditions'}
|
|
);
|
|
|
|
// Add alice as previous owner
|
|
transaction.inputs[0].owners_before = [alice.publicKey]
|
|
|
|
// Because the addition of crypto conditions, the id for the transaction has to be regenerated
|
|
delete transaction.id
|
|
transaction.id = sha3.sha3_256
|
|
.create()
|
|
.update(driver.Transaction.serializeTransactionIntoCanonicalString(transaction))
|
|
.hex()
|
|
|
|
// Alice has to sign this transfer because she is still the owner of the created asset
|
|
let signedCryptoConditionTx = driver.Transaction.signTransaction(transaction, alice.privateKey)
|
|
|
|
As you can see, we need to generate a new transactionId because we have added crypto conditions.
|
|
We do this with the js-sha3 package, you need to install this package through ``npm``:
|
|
|
|
``npm install --save js-sha3``
|
|
|
|
Don't forget to import the package in your code:
|
|
|
|
.. code-block:: js
|
|
|
|
import * as sha3 from 'js-sha3'
|
|
|
|
|
|
If you would like to see a more complex example, please have a look [here](https://github.com/bigchaindb/project-jannowitz/blob/code-examples/js-examples/crypto-conditions.js)
|
|
|
|
.. TODO: Document Utils when finished
|