btclib: a python3 library for 'bitcoin cryptography'

btclib is a python3 type annotated library intended for teaching and demonstration of the elliptic curve cryptography used in bitcoin.

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 University of Milano-Bicocca and Politecnico di Milano, its algorithms are not intended for production environments: they could be broken using side-channel attacks; moreover, they are often refactored without care for backward compatibility.

The library includes:

• modulo algebra functions (gcd, inverse, legendre symbol, square root)
• octets / integer / 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
• available curves: SEC 1 v1 and v2, NIST, Brainpool, and low cardinality test curves
• DSA signature with (transaction) DER encoding and (message) compact encoding
• Schnorr signature (according to bip-schnorr 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, addresses, WIFs
• BIP32 hierarchical deterministic wallets
• BIP39 wordlists and mnemonic for generating deterministic keys
• Electrum standard for mnemonic

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