Stwo Gnark Verifier

A Go-based implementation of a Zero-Knowledge verifier for the Stwo STARK proving system, built using the Gnark SNARK library.

This project implements a SNARK circuit designed to verify Cairo STARK proofs generated by Stwo Cairo (Starknet's next-generation Circle STARK prover). By porting the Stwo Circle STARKs verifier logic into a Groth16 or Plonk circuit, it enables efficient on-chain verification of Cairo ZKVM execution traces.

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🌟 About

Directly verifying Circle STARK proofs on-chain can be computationally expensive. This repository bridges that gap by providing:

• Recursive Proofs: Wrap a high-performance Stwo STARK proof into a constant-size SNARK proof.
• EVM Compatibility: Verify large Cairo ZKVM execution traces with minimal gas costs on Ethereum.
• Go-Powered Verification: Leverage the speed of Go and the Gnark framework for robust verifier implementations.

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🏗 Architecture

The project is structured to mirror the core components of the Stwo prover:

• m31/: Core arithmetic for the Mersenne-31 field.
• qm31/: Implementation of the quartic extension field used for statistical soundness and security.
• circle/: Circle curve operations, including domain definitions, group laws, and vanishing polynomials over the circle group.
• fri/: Implementation of the Circle FRI (Fast Reed-Solomon Interactive Oracle Proof of Proximity) protocol and high-performance Merkle verification using Blake2s.
• components/cairo_components/: AIR constraint evaluation logic for Cairo ZKVM opcodes and built-in functions.
• variables/: Optimized data structures for proof deserialization and Gnark circuit variables.

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🛠 Usage

Prerequisites

• Go 1.24+
• Rust/Cargo (only for generating custom shape files)

Running the Main Verifier

The entry point main.go demonstrates the full pipeline: loading a proof, compiling the circuit, performing a setup, generating a witness, and finally producing and verifying a Groth16 proof.

go run main.go

All Components (1 Query) Fixture

This repo includes a ready-to-run fixture for development:

• test_data/all_components_one_query.json
• test_data/all_components_one_query_shape.json

Run the verifier test directly:

go test -v --short ./verifier

Generating Shape Files

Shape JSON files define the circuit structure. They are produced by cairo-prove in the stwo-cairo ecosystem. To generate them, you need the circuit-data-gen branches:

1. Clone and link these repositories in the same parent directory:

• stwo-cairo
• stwo

2. Navigate to stwo-cairo/cairo-prove and run:

cargo run -- circuit-data \
  --path /path/to/stwo-gnark-verifier/test_data/all_components_one_query.json \
  --queries 1

Use --queries to match the proof’s stark_proof.config.fri_config.n_queries value.

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🧪 Testing

The project contains extensive unit tests for individual field arithmetic, Cairo opcodes, and the end-to-end verification flow.

# Run all tests
go test ./...

# Run tests with the short flag (skips heavy setup)
go test -short ./...

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🏷️ Versions

This project has been tested with:

• stwo @ c95edc65e3af652db0eda433dfa1b92831ca2b64
• stwo-cairo @ 5247e786a2c32299d653a5e8d1e5be65c0c219fe

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⚠️ Disclaimer

This implementation is currently under active development.

• Audit Status: This code has not yet been audited.

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🔗 Relevant Projects

• Stwo — StarkWare's Rust implementation of the Circle STARK protocol.
• Stwo-Cairo — An adapter to compile and prove execution traces of the Cairo ZKVM using the Stwo backend.
• Gnark — A fast ZK-SNARK library providing high-level APIs for designing arithmetic circuits in Go.

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