py-lean-multisig 0.2.0

Python bindings for leanMultisig: XMSS signatures + zkVM aggregation

py-lean-multisig

Python bindings for leanMultisig: XMSS signatures and zkVM-backed signature aggregation.

Requires Python >= 3.11. Wheels are built for Linux (x86_64, aarch64; glibc + musl) and macOS arm64.

Install

pip install py-lean-multisig

XMSS keygen / sign / verify

import py_lean_multisig as lm

# Key generation (seed is 32 bytes; slot range is inclusive)
sk, pk = lm.keygen(b"\x00" * 32, 0, 1023)

# Sign and verify (message is 32 bytes)
msg = b"\x42" * 32
sig = lm.sign(sk, msg, 5, rng_seed=b"\x99" * 32)  # rng_seed optional
lm.verify(pk, msg, sig, 5)

# Serialize/deserialize
pk2 = lm.PublicKey.from_bytes(pk.to_bytes())
sig2 = lm.Signature.from_bytes(sig.to_bytes())
assert pk == pk2 and sig == sig2

Aggregation

Aggregate N signatures over the same (message, slot) into a single proof, then verify.

import py_lean_multisig as lm

msg, slot = b"\x42" * 32, 5
pairs = [lm.keygen(bytes([i+1])*32, 0, 1023) for i in range(4)]
pks  = [pk for _, pk in pairs]
sigs = [lm.sign(sk, msg, slot, rng_seed=bytes([i+100])*32) for i, (sk, _) in enumerate(pairs)]

prover = lm.Prover(log_inv_rate=4)
verifier = lm.Verifier()

sorted_pks, agg = prover.aggregate(pks, sigs, msg, slot)
verifier.verify(sorted_pks, msg, agg, slot)

# AggregatedSignature bytes round-trip
agg2 = lm.AggregatedSignature.from_bytes(agg.to_bytes())

Hierarchical aggregation

Aggregated proofs are themselves zkVM-verifiable, so a Prover can fold existing aggregates into a new one via the children=.

This is useful for tree-shaped aggregation (each node aggregates its sub-tree's proofs) and for distributing proving work across machines (each shard produces a child proof and a coordinator folds them).

import py_lean_multisig as lm

msg, slot = b"\x42" * 32, 5

def _signers(seed_offset, n):
    pairs = [lm.keygen(bytes([seed_offset + i]) * 32, 0, 1023) for i in range(n)]
    pks  = [pk for _, pk in pairs]
    sigs = [lm.sign(sk, msg, slot, rng_seed=bytes([seed_offset + 100 + i]) * 32)
            for i, (sk, _) in enumerate(pairs)]
    return pks, sigs

prover   = lm.Prover(log_inv_rate=4)
verifier = lm.Verifier()

# Two disjoint sets of signers, aggregated independently.
pks_a, sigs_a = _signers(seed_offset=1,  n=2)
pks_b, sigs_b = _signers(seed_offset=50, n=2)
sorted_pks_a, agg_a = prover.aggregate(pks_a, sigs_a, msg, slot)
sorted_pks_b, agg_b = prover.aggregate(pks_b, sigs_b, msg, slot)

# Top level: no fresh raw signatures, just fold the two child proofs.
# Each child is the (sorted_pub_keys, AggregatedSignature) tuple
# returned by the previous aggregate() call.
sorted_pks_top, agg_top = prover.aggregate(
    [], [], msg, slot,
    children=[(sorted_pks_a, agg_a), (sorted_pks_b, agg_b)],
)

verifier.verify(sorted_pks_top, msg, agg_top, slot)

You can also mix raw signatures with children at the same level — e.g. fold two existing child aggregates plus a fresh batch of N raw signatures into one combined proof in a single aggregate() call.

Development

Uses uv for venv + dependency management

# One-time setup: create the venv, install maturin + dev deps, build
# and editable-install the extension.
uv venv
uv pip install maturin pytest mypy
uv run maturin develop --release --extras dev

# Run the test suite.
uv run pytest tests/ -v

# Verify the .pyi stubs match the runtime extension.
uv run python -m mypy.stubtest py_lean_multisig --allowlist stubtest_allowlist.txt

After Rust source changes, re-run uv run maturin develop --release to rebuild the extension.

License

MIT OR Apache-2.0