Equilibrium / Selected work / ZAIR — Zcash ↔ Namada

ZAIR — Zcash ↔ Namada

ZAIR, a zero-knowledge protocol connecting Zcash and Namada: holders prove note ownership and unspentness with privacy-preserving proofs (no nullifier or transaction details revealed) to claim assets on Namada.

Delivered
equilibriumco/zair equilibriumco/namada
Client Zcash Community Grants
Ecosystems Zcash · Namada
Stack Rust
Delivered by Eiger (now Equilibrium)

Overview

Equilibrium built ZAIR, a zero-knowledge protocol connecting the Zcash and Namada ecosystems, funded by Zcash Community Grants. It lets a Zcash shielded-note holder generate a ZK proof per note that demonstrates ownership and unspentness without revealing the Zcash nullifier or transaction details, so value can be claimed in the Namada ecosystem, a privacy-preserving, cross-ecosystem claim (“shielded airdrop”) protocol.

It is built on Zcash’s existing shielded-pool cryptography: the Sapling circuits (Groth16, via Bellman) and the Orchard circuits (Halo2), with the Namada side adapted to consume the proofs.

Deliverables

  • ZK circuit crates for proof generation and verification across Zcash’s Sapling (Groth16) and Orchard (Halo2) shielded pools, plus non-membership / Merkle utilities for proving unspentness.
  • Namada integration consuming the ZK proofs (equilibriumco/namada).
  • CLI and SDK tooling for scanning eligible notes and generating proofs.
  • Custom mdbook and cargo documentation.
  • Audit-preparation refactoring: restructuring the circuit crates to build directly on upstream forks rather than standalone crates, reducing the audit surface.

Technical highlights

  • Per-note ZK proofs of ownership and unspentness that do not reveal the Zcash nullifier, claimants find their eligible notes and prove each one.
  • Two proof systems matching Zcash’s shielded pools: Sapling via Groth16 (Bellman) and Orchard via Halo2.
  • Non-membership / Merkle-tree constructions to demonstrate unspentness.
  • Soundness checks of the constraints and constructions (trees, hashes).
  • Engineered for external review: circuit crates restructured onto upstream forks to shrink the audit surface, in preparation for a future external audit (the project is not yet audited).

Status

Delivered (around April 2026). Built openly at github.com/equilibriumco/zair (Zcash side) and github.com/equilibriumco/namada (Namada integration). Not audited: audit preparation was part of the scope, but no external audit has been performed.