VeChain Thor Devkit (SDK) in Python 3

Python 3 (Python 3.6+) library to assist smooth development on VeChain for developers and hobbyists.

Content
Public key, private key, address conversion.
Mnemonic Wallets.
HD Wallet.
Keystore.
Various Hashing functions.
Signing messages.
Verify signature of messages.
Bloom filter.
Transaction Assembling (Multi-task Transaction, MTT).
Fee Delegation Transaction (VIP-191).
Self-signed Certificate (VIP-192).
ABI decoding of "functions" and "events" in logs.

... and will always be updated with the newest features on VeChain.

Install

pip3 install thor-devkit -U

Caveat: Bip32 depends on the ripemd160 hash library, which should be present on your system within OpenSSL.

Type these in your terminal to see if they are available

> python3
> import hashlib
> print('ripemd160' in hashlib.algorithms_available)

Tutorials

Private/Public Keys

from thor_devkit import cry
from thor_devkit.cry import secp256k1

private_key = secp256k1.generate_privateKey()

public_key = secp256k1.derive_publicKey(private_key)

_address_bytes = cry.public_key_to_address(public_key)
address = '0x' + _address_bytes.hex()

print( address )
# 0x86d8cd908e43bc0076bc99e19e1a3c6221436ad0
print('is address?', cry.is_address(address))
# is address? True
print( cry.to_checksum_address(address) ) 
# 0x86d8CD908e43BC0076Bc99e19E1a3c6221436aD0

Sign & Verify Signature

from thor_devkit import cry
from thor_devkit.cry import secp256k1

# bytes
private_key = bytes.fromhex('7582be841ca040aa940fff6c05773129e135623e41acce3e0b8ba520dc1ae26a')
# bytes
msg_hash, _ = cry.keccak256([b'hello world'])

# Sign the message hash.
# bytes
signature = secp256k1.sign(msg_hash, private_key)

# Recover public key from given message hash and signature.
# bytes
public_key = secp256k1.recover(msg_hash, signature)

Mnemonic Wallet

from thor_devkit.cry import mnemonic

words = mnemonic.generate()
print(words)
# ['fashion', 'reduce', 'resource', 'ordinary', 'seek', 'kite', 'space', 'marriage', 'cube', 'detail', 'bundle', 'latin']

flag = mnemonic.validate(words)
print(flag)
# True

# Quickly get a Bip32 master seed for HD wallets. See below "HD Wallet".
seed = mnemonic.derive_seed(words)

# Quickly get a private key.
private_key = mnemonic.derive_private_key(words, 0)

HD Wallet

Hierarchical Deterministic Wallets. See bip-32 and bip-44.

from thor_devkit import cry
from thor_devkit.cry import hdnode

# Construct an HD node from words. (Recommended)
words = 'ignore empty bird silly journey junior ripple have guard waste between tenant'.split(' ')

hd_node = cry.HDNode.from_mnemonic(
    words,
    init_path=hdnode.VET_EXTERNAL_PATH
) # VET wallet, you can input other string values to generate BTC/ETH/... wallets.

# Or, construct HD node from seed. (Advanced)
seed = '28bc19620b4fbb1f8892b9607f6e406fcd8226a0d6dc167ff677d122a1a64ef936101a644e6b447fd495677f68215d8522c893100d9010668614a68b3c7bb49f'

hd_node = cry.HDNode.from_seed(
    bytes.fromhex(seed),
    init_path=hdnode.VET_EXTERNAL_PATH
) # VET wallet, you can input other string values to generate BTC/ETH/... wallets.

# Access the HD node's properties.
priv = hd_node.private_key()
pub = hd_node.public_key()
addr = hd_node.address()
cc = hd_node.chain_code()

# Or, construct HD node from a given public key. (Advanced)
# Notice: This HD node cannot derive child HD node with "private key".
hd_node = cry.HDNode.from_public_key(pub, cc)

# Or, construct HD node from a given private key. (Advanced)
hd_node = cry.HDNode.from_private_key(priv, cc)

# Let it derive further child HD nodes.
for i in range(0, 3):
    print('addr:', '0x'+hd_node.derive(i).address().hex())
    print('priv:', hd_node.derive(i).private_key().hex())

# addr: 0x339fb3c438606519e2c75bbf531fb43a0f449a70
# priv: 27196338e7d0b5e7bf1be1c0327c53a244a18ef0b102976980e341500f492425
# addr: 0x5677099d06bc72f9da1113afa5e022feec424c8e
# priv: 0xcf44074ec3bf912d2a46b7c84fa6eb745652c9c74e674c3760dc7af07fc98b62
# addr: 0x86231b5cdcbfe751b9ddcd4bd981fc0a48afe921
# priv: 2ca054a50b53299ea3949f5362ee1d1cfe6252fbe30bea3651774790983e9348

Keystore

from thor_devkit.cry import keystore

ks = {
    "version": 3,
    "id": "f437ebb1-5b0d-4780-ae9e-8640178ffd77",
    "address": "dc6fa3ec1f3fde763f4d59230ed303f854968d26",
    "crypto":
    {
        "kdf": "scrypt",
        "kdfparams": {
            "dklen": 32,
            "salt": "b57682e5468934be81217ad5b14ca74dab2b42c2476864592c9f3b370c09460a",
            "n": 262144,
            "r": 8,
            "p": 1
        },
        "cipher": "aes-128-ctr",
        "ciphertext": "88cb876f9c0355a89cad88ee7a17a2179700bc4306eaf78fa67320efbb4c7e31",
        "cipherparams": {
            "iv": "de5c0c09c882b3f679876b22b6c5af21"
        },
        "mac": "8426e8a1e151b28f694849cb31f64cbc9ae3e278d02716cf5b61d7ddd3f6e728"
    }
}
password = b'123456'

# Decrypt
private_key = keystore.decrypt(ks, password)

# Encrypt
ks_backup = keystore.encrypt(private_key, password)

Hash the Messages

from thor_devkit import cry

result, length = cry.blake2b256([b'hello world'])
result2, length = cry.blake2b256([b'hello', b' world'])
# result == result2

result, length = cry.keccak256([b'hello world'])
result2, length = cry.keccak256([b'hello', b' world'])
# result == result2

Bloom Filter

from thor_devkit import Bloom

# Create a bloom filter that can store 100 items.
_k = Bloom.estimate_k(100)
b = Bloom(_k)

# Add an item to the bloom filter.
b.add(bytes('hello world', 'UTF-8'))

# Verify
b.test(bytes('hello world', 'UTF-8'))
# True
b.test(bytes('bye bye blue bird', 'UTF-8'))
# False

Transaction

from thor_devkit import cry, transaction

# See: https://docs.vechain.org/thor/learn/transaction-model.html#model
body = {
    "chainTag": int('0x4a', 16), # 0x4a/0x27/0xa4 See: https://docs.vechain.org/others/miscellaneous.html#network-identifier
    "blockRef": '0x00000000aabbccdd',
    "expiration": 32,
    "clauses": [
        {
            "to": '0x7567d83b7b8d80addcb281a71d54fc7b3364ffed',
            "value": 10000,
            "data": '0x000000606060'
        },
        {
            "to": '0x7567d83b7b8d80addcb281a71d54fc7b3364ffed',
            "value": 20000,
            "data": '0x000000606060'
        }
    ],
    "gasPriceCoef": 128,
    "gas": 21000,
    "dependsOn": None,
    "nonce": 12345678
}

# Construct an unsigned transaction.
tx = transaction.Transaction(body)

# Access its properties.
tx.get_signing_hash() == cry.blake2b256([tx.encode()])[0] # True

tx.get_signature() == None # True

tx.get_origin() == None # True

tx.get_intrinsic_gas() == 37432 # estimate the gas this tx gonna cost.

# Sign the transaction with a private key.
priv_key = bytes.fromhex('7582be841ca040aa940fff6c05773129e135623e41acce3e0b8ba520dc1ae26a')
message_hash = tx.get_signing_hash()
signature = cry.secp256k1.sign(message_hash, priv_key)

# Set the signature on the transaction.
tx.set_signature(signature)

# Tx origin?
print(tx.get_origin())
# 0xd989829d88b0ed1b06edf5c50174ecfa64f14a64

# Tx id?
print(tx.get_id())
# 0xda90eaea52980bc4bb8d40cb2ff84d78433b3b4a6e7d50b75736c5e3e77b71ec

# Tx encoded into bytes, ready to be sent out.
encoded_bytes = tx.encode()

# pretty print the encoded bytes.
print('0x' + encoded_bytes.hex())

# http POST transaction to send the encoded_bytes to VeChain...
# See the REST API details:
# testnet: https://sync-testnet.vechain.org/doc/swagger-ui/
# mainnet: https://sync-mainnet.vechain.org/doc/swagger-ui/

Transaction (VIP-191)

https://github.com/vechain/VIPs/blob/master/vips/VIP-191.md

from thor_devkit import cry, transaction

delegated_body = {
    "chainTag": 1,
    "blockRef": '0x00000000aabbccdd',
    "expiration": 32,
    "clauses": [
        {
            "to": '0x7567d83b7b8d80addcb281a71d54fc7b3364ffed',
            "value": 10000,
            "data": '0x000000606060'
        },
        {
            "to": '0x7567d83b7b8d80addcb281a71d54fc7b3364ffed',
            "value": 20000,
            "data": '0x000000606060'
        }
    ],
    "gasPriceCoef": 128,
    "gas": 21000,
    "dependsOn": None,
    "nonce": 12345678,
    "reserved": {
        "features": 1
    }
}

delegated_tx = transaction.Transaction(delegated_body)

# Indicate it is a delegated Transaction using VIP-191.
assert delegated_tx.is_delegated() == True

# Sender
addr_1 = '0xf9ea4ba688d55cc7f0eae0dd62f8271b744637bf'

priv_1 = bytes.fromhex('58e444d4fe08b0f4d9d86ec42f26cf15072af3ddc29a78e33b0ceaaa292bcf6b')


# Gas Payer
addr_2 = '0x34b7538c2a7c213dd34c3ecc0098097d03a94dcb'

priv_2 = bytes.fromhex('0bfd6a863f347f4ef2cf2d09c3db7b343d84bb3e6fc8c201afee62de6381dc65')


h = delegated_tx.get_signing_hash() # Sender hash to be signed.
dh = delegated_tx.get_signing_hash(addr_1) # Gas Payer hash to be signed.

# Sender sign the hash.
# Gas payer sign the hash.
# Concat two parts to forge a legal signature.
sig = cry.secp256k1.sign(h, priv_1) + cry.secp256k1.sign(dh, priv_2)

delegated_tx.set_signature(sig)

assert delegated_tx.get_origin() == addr_1
assert delegated_tx.get_delegator() == addr_2

Sign/Verify Certificate (VIP-192)

https://github.com/vechain/VIPs/blob/master/vips/VIP-192.md

from thor_devkit import cry
from thor_devkit.cry import secp256k1
from thor_devkit import certificate

# My address.
address = '0xd989829d88b0ed1b06edf5c50174ecfa64f14a64'
# My corresponding private key.
private_key = bytes.fromhex('7582be841ca040aa940fff6c05773129e135623e41acce3e0b8ba520dc1ae26a')

# My cert.
cert_dict = {
    'purpose': 'identification',
    'payload': {
        'type': 'text',
        'content': 'fyi'
    },
    'domain': 'localhost',
    'timestamp': 1545035330,
    'signer': address
}

# Construct a cert, without signature.
cert = certificate.Certificate(**cert_dict)

# Sign the cert with my private key.
sig_bytes = secp256k1.sign(
    cry.blake2b256([
        certificate.encode(cert).encode('utf-8')
    ])[0],
    private_key
)
signature = '0x' + sig_bytes.hex()

# Mount the signature onto the cert.
cert_dict['signature'] = signature

# Construct a cert, with signature.
cert2 = certificate.Certificate(**cert_dict)

# Verify, if verify failed it will throw Exceptions.
certificate.verify(cert2)

ABI

Encode function name and parameters according to ABI.

from thor_devkit import abi

abi_dict = {
        "constant": False,
        "inputs": [
            {
                "name": "a1",
                "type": "uint256"
            },
            {
                "name": "a2",
                "type": "string"
            }
        ],
        "name": "f1",
        "outputs": [
            {
                "name": "r1",
                "type": "address"
            },
            {
                "name": "r2",
                "type": "bytes"
            }
        ],
        "payable": False,
        "stateMutability": "nonpayable",
        "type": "function"
}

# Verify if abi_dict is in good shape.
f1 = abi.FUNCTION(abi_dict)

# Get a function instance of the abi.
f = abi.Function(f1)

# Get function selector:
selector = f.selector.hex()
selector == '27fcbb2f'

# Encode the function input parameters.
r = f.encode([1, 'foo'], to_hex=True)
r == '0x27fcbb2f000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000003666f6f0000000000000000000000000000000000000000000000000000000000'

# Decode function return result according to abi.
data = '000000000000000000000000abc000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000003666f6f0000000000000000000000000000000000000000000000000000000000'

r = f.decode(bytes.fromhex(data))
# {
#     "0": '0xabc0000000000000000000000000000000000001',
#     "1": b'666f6f',
#     "r1": '0xabc0000000000000000000000000000000000001',
#     "r2": b'666f6f'
# }

Decode logs according to data and topics.

from thor_devkit import abi

e2 = abi.EVENT({
    "anonymous": True,
    "inputs": [
        {
            "indexed": True,
            "name": "a1",
            "type": "uint256"
        },
        {
            "indexed": False,
            "name": "a2",
            "type": "string"
        }
    ],
    "name": "E2",
    "type": "event"
})

ee = abi.Event(e2)

# data in hex format.
r = ee.decode(
    data=bytes.fromhex('00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000003666f6f0000000000000000000000000000000000000000000000000000000000'),
    topics=[
        bytes.fromhex('0000000000000000000000000000000000000000000000000000000000000001')
    ]
)

# r == { "0": 1, "1": "foo", "a1": 1, "a2": "foo" }

Tweak the Code

Layout

.
├── LICENSE
├── README.md
├── requirements.txt
└── thor_devkit
    ├── __init__.py
    ├── abi.py
    ├── bloom.py
    ├── certificate.py
    ├── cry
    │   ├── __init__.py
    │   ├── address.py
    │   ├── blake2b.py
    │   ├── hdnode.py
    │   ├── keccak.py
    │   ├── keystore.py
    │   ├── mnemonic.py
    │   ├── secp256k1.py
    │   └── utils.py
    ├── rlp.py
    └── transaction.py

Local Development

# install dependencies
make install
# test code
make test

Knowledge

Name	Bytes	Description
private key	32	random number
public key	65	uncompressed, starts with "04"
address	20	derived from public key
keccak256	32	hash
blake2b256	32	hash
message hash	32	hash of a message
signature	65	signing result, last bit as recovery parameter
seed	64	used to derive bip32 master key