Backend Services

All backend services are Fastify applications running on Node.js 24.

RPC Proxy

The core orchestration service. Intercepts JSON-RPC calls from wallets.

Key responsibilities:

• Parse transaction intent

• Select funding notes

• Generate ZK proofs

• Submit to relayer

• Maintain per-user state (LMDB)

Internal services:

• ShieldingService — Orchestrates proof generation and relayer submission

• NoteTreeService — Local Merkle tree for membership proofs

• NotesScanner — Background scan of blockchain events

• NotesStorage — Per-user note storage (LMDB)

• KeyStorageService — Per-user key storage

• KeyRegistryService — Syncs on-chain key registry

• GasEstimateService — Pre-computed gas estimates

• ExchangeRatesService — Token price conversion for fee estimation

• AccessTableService — Maps access tokens to addresses

State persistence: LMDB database at apps/rpc-proxy/lmdb-data/

Relayer

Submits shielded transactions to the blockchain.

Key responsibilities:

• Receive proof + params from the proxy

• Submit contract calls (shieldedTransfer, shieldedWithdrawal, shieldedSwap)

• Pay gas fees (reimbursed from transaction fee allocation)

• Return transaction receipt

Guard

Approves or rejects deposits into the privacy pool.

Key responsibilities:

• Monitor DepositPending events

• Screen depositor addresses

• Call approveDeposit() or rejectDeposit()

• Generate and publish revocation keys

Faucet

Distributes testnet funds.

Key responsibilities:

• Provide testnet ETH and ERC-20 tokens

• Active only on testnet deployments

• Used during onboarding flow

Explorer

Block explorer for the Nullmask network. Displays public on-chain data.

Running Individual Services

cd web

# All services
pnpm dev

# Individual services
pnpm --filter rpc-proxy dev
pnpm --filter relayer dev
pnpm --filter guard dev
pnpm --filter faucet dev
pnpm --filter app dev
pnpm --filter explorer dev

# All services for local Hardhat testing
pnpm dev:hardhat