Privacy Pool Circuits

This package contains the zero-knowledge circuit implementations for the Privacy Pool protocol. The circuits are written in Circom and are designed to work together to enable private withdrawals with membership proofs.

Circuit Architecture

The protocol implements three main circuits that work together:

Withdrawal Circuit

The withdrawal circuit verifies that a user can privately withdraw funds from the protocol. It takes as input:

The withdrawal amount and details
The unique related commitments identifier (label)
A state root and ASP (Association Set Provider) root
A proof of inclusion in the state tree
A proof of inclusion in the ASP tree
Nullifier and commitment secrets

The circuit ensures the withdrawal is valid by verifying:

The user knows the preimage of the commitment
The commitment exists in the state tree
The comimtment label is included in the ASP tree
The withdrawal amount is valid and matches the commitment

LeanIMT Circuit

The LeanIMT (Lean Incremental Merkle Tree) circuit handles merkle tree operations. It implements an optimized merkle tree that:

Supports dynamic depth
Optimizes node computations by propagating single child values
Verifies inclusion proofs efficiently

Commitment Circuit

The commitment circuit manages the hashing and verification of commitments. It:

Computes commitment hashes from input values and secrets
Generates nullifier hashes for preventing double-spending
Creates precommitment hashes for privacy preservation

Development

Prerequisites

Node.js 20+
Yarn
circom 2.2.0+

Building

# Compile circuits
yarn compile

Testing

# Run circuit tests
yarn test

Generating Groth16 Solidity verifiers

# Generate verifier for the withdrawal circuit
yarn gencontract:withdraw

# Generate verifier for the commitment circuit
yarn gencontract:commitment

Directory Structure

circuits/
├── circuits/
│   ├── commitment.circom     # Commitment circuit
│   ├── merkleTree.circom     # LeanIMT circuit
│   └── withdraw.circom       # Withdrawal circuit
└── tests/                    # Circuit tests

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