btclib: a python3 library for 'bitcoin cryptography'

btclib is a python3 (>=3.8) type annotated library intended for teaching/learning/using bitcoin, its blockchain, and the associated elliptic curve cryptography.

It does not have external requirements or dependencies; to install (and upgrade) it:

python -m pip install --upgrade btclib

Originally developed for the Bitcoin and Blockchain Technology course at the University of Milano-Bicocca, the library 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 includes:

• modulo algebra functions (gcd, inverse, legendre symbol, square root)
• octets / integer / varint / point conversion 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
• EC Schnorr signature (according to BIP340 bitcoin standardization)
  • batch validation
  • threshold signature (see test-suite)
  • MuSig multi-signature (see test-suite)
• Borromean ring signature
• RFC 6979 to make signature schemes deterministic
• 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 wallets
• BIP39 wordlists and mnemonic for generating deterministic keys
• Electrum standard for mnemonic
• Script encoding/decoding
• nulldata, p2pk, p2pkh, multi-sig, p2sh, p2wpkh, and p2wsh ScriptPubKeys

A very extensive test suite reproduces results from major official sources and covers 100% of the library code base.

The library development is actively supported by the Digital Gold Institute