Nox

Demo

About

Nox is a privacy-preserving trading layer for perpetual futures. Users deposit tokens into a dark pool where balances are represented as ZK notes instead of public addresses. A `PrivacyProxy` owns all on-chain positions on the underlying `ClearingHouseV2`, while real user ownership is tracked off-chain using signatures derived from a private “dark-pool secret.” This lets traders open/close positions and move collateral without revealing their identity or balances on-chain. Funds flow in two directions: - Into the DEX: Users prove note ownership in the `TokenPool` using ZK (withdraw/transfer proofs). The pool “approvesWithdrawal” and the `PrivacyProxy` pulls collateral, credits private free-collateral for the user’s pubkey, and deposits into `ClearingHouseV2`. - Back to the dark pool: Users sign a withdraw intent; the proxy withdraws collateral from `ClearingHouseV2` and calls `TokenPool.depositFor` to mint a new private note to the user’s receiver hash. An HTTP backend indexes on-chain events and serves a privacy-aware API. It tracks open/historical positions per user pubkey and maintains a local view of unspent notes keyed by receiver hash. The frontend bootstraps a per-user secret via a signed message, derives a pubkey and receiver hash, and interacts with the backend using signed headers. As a result, positions and balances can be queried privately, while the public ledger only shows activity of the proxy and the DEX.

How it's made

Smart contracts (Solidity): - TokenPool: Private note system with Poseidon commitments, incremental Merkle tree, nullifiers, and two ZK verifiers (Claim and Withdraw/Transfer). Supports deposit, withdraw, transfer, claim, approveWithdrawal, and depositFor. - PrivacyProxy: Bridges the dark pool and ClearingHouseV2. Manages per-user free collateral mapped by a pubkey (keccak of the user’s secret EOA). Requires ECDSA signatures over action-specific messages to authorize trading or withdrawals. - ClearingHouseV2: Minimal perp engine with collateral accounting, fees, PnL, margin checks, liquidations, and position events. Collateral token is mintable for positive PnL to settle profit into the system. - ZK verifiers: Ultra Honk-based on-chain verifiers for claim and withdraw/transfer circuits. - Libraries: Poseidon2, Merkle tree, ProofLib for public input decoding. ZK Circuits (Noir): - Claim circuit merges a new claim with an existing commitment via Lean IMT inclusion proofs and Poseidon hashing, enforcing correct receiver secret and (optional) previous state accumulation. - Withdraw/Transfer circuit (in repo) validates spending via nullifier, root inclusion, and new commitment computation for change notes. Backend (Rust, Axum + sled + ethers): - Dual services: API server and indexer. - Indexer queries logs from PrivacyProxy, ClearingHouseV2, and TokenPool (NoteCreated/NoteClaimed) and persists: - Open positions by user pubkey (private), historical positions (closed/liquidated), and public positions by EOA for transparency. - Unspent notes by receiver hash, allowing users to fetch notes privately using only their hash. - API endpoints require signed headers. Server derives the same pubkey as the contracts (keccak of recovered EOA), aligning off-chain identity with on-chain checks. Also stores small encrypted metadata blobs per user (e.g., last-used nullifier nonce and latest commitment info). Frontend (Vite + React + wagmi + Zustand + axios): - On “private mode” init, asks the user to sign a message; derives a private key used to form a “secret wallet,” then derives: - pubKey: keccak(address(secretWallet)) - receiverHash: Poseidon(receiverSecret) - Uses signed headers to call the backend for: - Private open/historical positions pagination - Unspent notes for the user’s receiver hash - Small encrypted metadata storage (to track nullifier nonce and commitment leaf index) - Public mode can view public open positions by EOA via indexer endpoints. Integrations and hacky bits: - The proxy pattern concentrates all public DEX activity under PrivacyProxy, hiding actual owners while preserving correctness with signatures bound to a derived pubkey. - sled is used for a lightweight append-only style DB to serve fast pagination and note lookups without external infra. - The indexer converts websocket RPC to HTTP polling to safely chunk through historical ranges and avoid missed events, with retry loops and chunking to handle RPC limits. - Mint-on-profit in ClearingHouseV2 simplifies PnL settlement for a hackathon demo environment. Partner/stack benefits: - Noir/Honk verifiers on-chain let us prove note ownership and state transitions without revealing identities. - Ethers + Axum provide a fast Rust indexer and HTTP server. - wagmi and ethers on the frontend streamline wallet interactions and message signing. This delivers privacy-preserving perp trading: users keep balances and actions private in a ZK note system, while a proxy safely intermediates interaction with a standard DEX.