A Python library for ‘bitcoin cryptography’

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btclib is a Python3 type annotated library intended for teaching, learning, and using bitcoin; the focus is on elliptic curve cryptography and bitcoin’s blockchain.

It is rigorously and extensively tested: the test suite covers 100% of the code base and reproduces results from both informal and major reference sources.

Originally developed for the Bitcoin and Blockchain Technology course at the University of Milano-Bicocca, btclib is not intended for production environments: it is often refactored for improved clarity, without care for backward compatibility; moreover, some of its algorithms could be broken using side-channel attacks.

The library is not limited to the bitcon elliptic curve secp256k1; anyway, FFI bindings to libsecp256k1 (the optimized C library used by Bitcoin Core) are available for this curve and used by default.

Included features are:

  • modulo algebra functions (gcd, inverse, legendre symbol, square root)

  • octets / integer / point / var_int / var_bytes helper functions

  • elliptic curve class

    • fast algebra implemented using Jacobian coordinates

    • double scalar multiplication (Straus’s algorithm, also known as Shamir’s trick)

    • multi scalar multiplication (Bos-coster’s algorithm)

    • point simmetry solution: odd/even, low/high, and quadratic residue

    • elliptic curves: SEC 1 v1 and v2, NIST, Brainpool, and low cardinality test curves

  • ECDSA signature with (transaction) DER encoding

  • ECDSA signature with (message) compact encoding: standard p2pkh and BIP137/Electrum extensions to p2wpkh and p2wpkh-p2sh

  • RFC 6979 for deterministic signature schemes

  • EC Schnorr signature (according to BIP340 bitcoin standardization)

    • batch validation

    • threshold signature (see test-suite)

    • MuSig multi-signature (see test-suite)

  • Borromean ring signature

  • Sign-to-contract commitment

  • Diffie-Hellman

  • Pedersen committment

  • Base58 encoding/decoding

  • p2pkh/p2sh addresses and WIFs

  • Bech32 encoding/decoding

  • p2wpkh/p2wsh native SegWit addresses and their legacy p2sh-wrapped versions

  • BIP32 hierarchical deterministic key chains

  • SLIP132 key versions (xprv, yprv, zprv, Yprv, Zprv, tprv, uprv, vprv, and Uprv) with corresponding mapping to p2pkh/p2sh, p2wpkh-p2sh, p2wpkh, p2wsh-p2sh, p2wsh and p2tr addresses

  • BIP39 wordlists and mnemonic for generating deterministic keys

  • Electrum standard for mnemonic

  • Script encoding/decoding

  • nulldata, p2pk, p2ms, p2pkh, p2sh, p2wpkh, p2wsh and p2tr ScriptPubKeys

  • BlockHeader and Block data classes

  • OutPoint, TxIn, TxOut, and TX data classes

  • legacy, segwit_v0 and taproot transaction hash signatures

  • BIP174 partially signed bitcoin transactions (PSBT): PsbtIn, PbstOut, and Psbt data classes

To install (and/or upgrade) btclib:

python -m pip install --upgrade btclib

You might want to install btclib into a python virtual environment; e.g. from the root folder:

Shell:

python -m venv venv_btclib
source ./venv_btclib/bin/activate
python -m pip install --upgrade btclib

Windows CMD or PowerShell:

python -m venv venv_btclib
.\venv_btclib\Scripts\activate
python -m pip install --upgrade btclib

Windows Git bash shell:

python -m venv venv_btclib
cd ./venv_btclib/Scripts
. activate
cd ../..
python -m pip install --upgrade btclib

See CONTRIBUTING if you are interested in btclib develoment.

See SECURITY if you have found a security vulnerability.