reference

Vega reference implementation (pyvega)

A small, dependency-light pure-Python implementation of the Vega-MC proof system (the only third-party package is pycryptodome, for Keccak). It is the authoritative reference for the protocol: rather than restating the algorithm in prose, the book points here, and conformance is established by mutual acceptance with the shipped Rust prover/verifier.

Status: preliminary — an executable specification optimized for clarity, limited to the fixed cubic circuit, and cross-conformance tested against the Rust implementation in both directions. It has not been independently security-audited and its internals may change; treat it as a spec and teaching aid, not a production prover.

Because the proof is randomized (zero-knowledge), conformance is not byte identity of proofs. Instead it is verifier acceptance in both directions:

• the Rust prover's proof is accepted by this Python verifier, and
• this Python prover's proof (and its Python-generated verifier key) is accepted by the real Rust verifier.

The worked example throughout is the tiny cubic relation y = x³ + x + 5 (x = 2, y = 15) — the same CubicCircuit the Rust test-suite uses — so every structural feature of the protocol is exercised while staying checkable by hand.

Layout

pyvega/
  params.py            curve/field integer constants
  field.py  polys.py   scalar field arithmetic, MLE / eq / sparse polynomials
  curve.py             base field, curve arithmetic, point (de)compression
  codec.py             bincode reader primitives
  transcript.py        Keccak Fiat-Shamir transcript
  proof.py  vk.py      proof / verifier-key parsers (wire -> structs)
  commitment.py  hyrax.py  instance.py  nifs.py  sumcheck.py  spartan.py
                       verifier building blocks
  verify.py            the top-level verifier (acceptance predicate)

  app_circuit.py       the cubic application R1CS + witness
  verifier_circuit.py  emitter for the fixed in-circuit verifier shape/witness
  prover*.py           the prover: commit, core (NIFS + sum-checks), finish
                       (Nova fold + relaxed Spartan + ZK IPA), serialize
  setup.py             stand-alone key-gen + verifier-key serialization

Running

Every test runs under stock python3 (the implementation is pure Python). Install the one dependency once with python3 -m pip install pycryptodome.

# deterministic core (byte-exact vs Rust fixtures)
python3 reference/tests/test_proof_parse.py
python3 reference/tests/test_transcript.py
python3 reference/tests/test_vk_digest.py

# Rust prover -> Python verifier accepts
python3 reference/tests/test_verify.py

# Python prover -> Python verifier accepts (self-check)
python3 reference/tests/test_prove_finish.py

# fully stand-alone: Python setup + prove + verify, then write the fixtures
python3 reference/tests/test_standalone.py

The two cross-conformance gates against the real Rust verifier are #[ignore] tests in tests/reference_conformance.rs:

# Python proof against the Rust-exported verifier key
cargo test --test reference_conformance verify_python_proof -- --ignored --nocapture

# Python proof against a Python-generated verifier key (zero Rust setup)
cargo test --test reference_conformance verify_python_standalone -- --ignored --nocapture

Fixtures

reference/fixtures/cubic/transcript_vector.json (a frozen Keccak transcript known-answer vector consumed by test_transcript.py) is the only committed fixture. Every other fixture -- verifier keys, proofs, digests, and the meta.json metadata (circuit info and expected public values) -- is git-ignored and regenerated on demand, because the keys are large and the proofs are randomized. Regenerate them with:

Fixture	Regenerate with
cubic/meta.json, cubic/proof.bin, cubic/vk.bin, cubic/vk_digest.bin	cargo test --lib export_cubic_fixtures -- --ignored
cubic/transcript_vector.json (Keccak transcript known-answer vector)	cargo test --lib export_transcript_vector -- --ignored
cubic/python_proof.bin (reference proof vs the Rust vk.bin)	python3 reference/tests/test_prove_finish.py
cubic/python_vk.bin, cubic/python_standalone_proof.bin (fully stand-alone)	python3 reference/tests/test_standalone.py

The verify_python_proof gate needs cubic/vk.bin + cubic/python_proof.bin; the verify_python_standalone gate needs cubic/python_vk.bin + cubic/python_standalone_proof.bin. Regenerate the relevant fixtures before running a gate on a fresh checkout.