About this repo

Barebones Python 3.6+ implementation (no dependencies/standard lib only) of some common cryptographic functions for educational purposes. Feel free to fork the repo and play around with it. Performance is ..abysmal but otherwise it works fine. Please do not use this for anything serious because I am not a security expert.

Install

$ pip install git+https://github.com/mcdallas/cryptotools.git@master#egg=cryptotools

Examples

HD Wallets

from cryptotools.BTC import Xprv

>>> m = Xprv.from_mnemonic('impulse prize erode winner pupil fun off addict ...')
>>> m.encode()
'xprv9s21ZrQH143K38bNJiHY54kkjio8o6aw3bRjCbzi8KgRxNy98avUribz1wk85ToSUV2VwVuc73NJWc2YGwpMtqz7bBFUh9Q77RtJeuh2zvy'

>>> m/44/0/0/0
Xprv(path=m/44/0/0/0, key=L1WKXyMwKnp8wPwAtjwiKWunACY5RSUXAzmS6jDRRHcHnDbeRiKu)

>>> m/0./123/5.  # Use floats for hardened path, alternative is // e.g m//0/123//5
Xprv(path=m/0h/123/5h, key=L3qskbdzgNu4kwjx2QU63q59khpEHVaSbqd2Pc268Jngiha6mbfQ)

>>> M = m.to_xpub()

>>> (m/123/456).to_xpub() == M/123/456
True

>>> (m/44./0./0./0/0).address('P2PKH')  # bip44
'1BTYXdyrBh1yRCDpqyDhoQG896bnzqtaPz'

>>> (m/84./0./0./0/0).address('P2WPKH')  # bip84
'bc1qjnx8cq32z2t72tsmuwql3wz22lywlpcm3w52lk'

BIP39 checksum

Say you lost the first of your 12 mnemonic words and you want to filter out the possible mnemonics from 2048 to 128 by veryfing the checksum

from cryptotools.BTC.HD import check, WORDS

phrase = "{x} decrease enjoy credit fold prepare school midnight flower wrong false already"

for word in WORDS:
    mnemonic = phrase.format(x=word)
    if check(mnemonic):
        print(mnemonic)

Sign/Verify message:

import secrets
from cryptotools.ECDSA.secp256k1 import generate_keypair, Message

private, public = generate_keypair()

>>> message = Message(secrets.token_bytes(32))
>>> sig1 = message.sign(private)          # ECDSA
>>> sig2 = message.sign_schnorr(private)  # Schnorr
>>> message.verify(sig1, public)
True
>>> message.verify(sig2, public)
True

Verify a transaction:

from cryptotools.BTC import Transaction

tx = Transaction.get('454e575aa1ed4427985a9732d753b37dc711675eb7c977637b1eea7f600ed214')

>>> tx
Transaction(inputs=1, outputs=2)

>>> tx.outputs
[Output(type=P2SH, value=0.0266 BTC),
 Output(type=P2WSH, value=0.00468 BTC)]

>>> tx.verify()  # this runs the bitcoin script
True

Create a transaction and submit it automatically

import os
os.environ['CRYPTOTOOLS_NETWORK'] = 'test'  # sets network to testnet (before library import)

from cryptotools.BTC import PrivateKey, send

key = PrivateKey.from_hex('mysupersecretkey')

>>> send(source='n4SbPWR6EmQMsWaQVYYFXiJgjweGKE4XnQ', to={'n2NGrooSecJaiD6ssp4YqFoj9eZ7GrCJ66': 0.46}, fee=0.01, private=key)
'907b92969cb3a16ddb45591bf2530f177b7f10cef4e62c331596a84f66c3b8c3'  # txid

Create and broadcast manually

import os
os.environ['CRYPTOTOOLS_NETWORK'] = 'test'

from cryptotools.BTC import PrivateKey, Address

private = PrivateKey.from_hex('mysupersecretkey')
address = Address('n2NGrooSecJaiD6ssp4YqFoj9eZ7GrCJ66')

>>> address.balance()
0.55

>>> send_to = {'n4SbPWR6EmQMsWaQVYYFXiJgjweGKE4XnQ': 0.1, 'n2NGrooSecJaiD6ssp4YqFoj9eZ7GrCJ66': 0.4}
>>> tx = address.send(to=send_to, fee=0.05, private=private)

>>> tx
Transaction(inputs=1, outputs=2)

>>> tx.inputs[0].is_signed()
True

>>> tx.verify()  # Make sure transaction is valid before broadcasting
True

>>> tx.broadcast()
'Transaction Submitted'

Create keys/addresses (including segwit)

from cryptotools.BTC import generate_keypair, push, script_to_address, OP
private, public = generate_keypair()

>>> private.hex()
'de4f177274d29f88a5805333e10525f5dd41634455dfadc8849b977802481ccd'

>>> private.wif(compressed=False)
'5KWCAYLo35uZ9ibPTzTUDXESTE6ne8p1eXviYMHwaoS4tpvYCAp'

>>> public.hex()
'047e30fd478b44869850352daef8f5f7a7b5233044018d465431afdc0b436c973e8df1244189d25ae73d90c90cc0f998eb9784adecaecc46e8c536d7d6845fa26e'

>>> public.to_address('P2PKH')
'19dFXDxiD4KrUTNFfcgeekFpQmUC553GzW'

# Simple <key> <OP_CHECKSIG> script
>>> script = push(public.encode(compressed=True)) + OP.CHECKSIG.byte
>>> script_to_address(script, 'P2WSH')
'bc1q8yh8l8ft3220q328hlapqhflpzy6xvkq6u36mctk8gq5pyxm3rwqv5h5dg'

# nested P2WSH into P2SH -- use with caution
>>> script_to_address(script, 'P2WSH-P2SH')
'34eBzenHJEdk5PK9ojuuBZvCRtNhvvysYZ'

from cryptotools.ECDSA.secp256k1 import CURVE, PrivateKey
private = PrivateKey.random()

>>> private.int()
8034465994996476238286561766373949549982328752707977290709076444881813294372

>>> public = private.to_public()
>>> public
PublicKey(102868560361119050321154887315228169307787313299675114268359376451780341556078, 83001804479408277471207716276761041184203185393579361784723900699449806360826)

>>> public.point in CURVE
True

>>> public.to_address('P2WPKH')
'bc1qh2egksgfejqpktc3kkdtuqqrukrpzzp9lr0phn'

Configuration --------

By default the library communicates with the bitcoin network (for fetching transactions) via a block explorer but as an alternative you can use a bitcoin node via it's RPC interface. Just set the following enviromental variables

CRYPTOTOOLS_BACKEND=rpc
CRYPTOTOOLS_BACKEND=localhost
CRYPTOTOOLS_RPC_PORT=8332

and optionally

CRYPTOTOOLS_RPC_USER=myuser
CRYPTOTOOLS_RPC_PW=mypassword

to switch the network to Testnet set

CRYPTOTOOLS_NETWORK=test

to run tests

$ python -m unittest

from the project directory