zkFair

zkFair is a framework for generating and verifying zero-knowledge proofs of ML model fairness. Providers register models, commit query batches, and respond to fairness audits — all using ZK proofs on-chain. Users get cryptographic guarantees that deployed models satisfy demographic parity, without the provider ever revealing model weights or training data.

Documentation | Live Demo

Key Contributions

1. Zero-Knowledge Fairness Protocol

Two Noir ZK circuits enable privacy-preserving fairness verification:

• Training Certification — proves a model satisfies demographic parity on its training dataset, without revealing weights or data
• Batch Auditing — proves ongoing fairness on random samples from deployed inference batches, enabling continuous runtime monitoring

2. Economic Incentive Mechanism

A Solidity smart contract enforces honest participation through staking and slashing:

• Providers stake ETH to register models; dishonest behavior (missed audits, invalid proofs) results in stake forfeiture
• Auditors stake to challenge batches; valid challenges are rewarded from the provider's stake
• 24-hour response deadlines with automatic slashing for non-compliance

3. Client-Side Fraud Detection (Sentinel)

Users receive signed receipts for every inference query. The Sentinel system detects two classes of provider fraud:

• Non-inclusion — a query was made but never appeared in any committed batch
• Fraudulent inclusion — a query was batched with tampered data (different features or prediction)

Both dispute types are provable on-chain using the signed receipt as evidence.

4. Open-Source Modular Implementation

A production-ready TypeScript SDK and toolchain:

• SDK (@zkfair/sdk) — core library with contract interaction, proof generation, Poseidon hashing, Merkle trees, and provider/client utilities
• ZK Circuits (@zkfair/zk-circuits) — Noir circuits compiled to UltraHonk via @aztec/bb.js
• Smart Contract (@zkfair/contracts) — Solidity contract with model registry, batch commitments, audit lifecycle, and dispute resolution
• Apps — CLI for providers, React dashboard, inference server, and off-chain attestation service

Repo Structure

apps/
  cli/           Command-line interface for providers
  web/           React dashboard (model registry, audit tracking)
  server/        Hono inference server (ONNX model, query logging, auto-batching)
  attestation/   Off-chain proof verification + signed attestations
  www/           Landing page + documentation site

packages/
  sdk/           TypeScript SDK shared across all apps
  contracts/     Solidity smart contract (Foundry)
  zk-circuits/   Noir ZK circuits (training + fairness audit)

Getting Started

# Install dependencies
bun install

# Run all apps in dev (starts local anvil chain + all services)
bun run dev

# Run a single app
turbo run dev --filter=web
turbo run dev --filter=server

# Build everything
turbo run build

# Run contract tests
cd packages/contracts && bun run test

# Run SDK tests
cd packages/sdk && bun test

# Compile ZK circuits
cd packages/zk-circuits && bun run compile