> For the complete documentation index, see [llms.txt](https://docs.nullmask.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nullmask.pro/components.md).
# Components
### Overview
Nullmask consists of four main components that work together to provide privacy-preserving transactions.
### Wallet
Any standard EVM wallet that supports:
* **Custom networks** (custom RPC endpoints)
* **`personal_sign`** method (for key generation)
* **EIP-1559** transactions
### RPC Proxy
The core orchestration service. It sits between the wallet and the blockchain, intercepting JSON-RPC calls.
**Responsibilities:**
* **Key management** — Generates viewing keys and receiving keys from wallet signatures; stores them locally
* **Transaction shielding** — Parses transaction intent, selects funding notes, generates ZK proofs
* **Balance tracking** — Scans the blockchain for new notes, trial-decrypts them, maintains shielded balances
* **State isolation** — Per-user state via access tokens (HTTP-only cookies)
* **Key registry sync** — Caches on-chain receiving keys for privacy-preserving lookups
### Relayer
Executes shielded transactions on behalf of users.
**Responsibilities:**
* Receives shielded transaction data (proof + public inputs) from the proxy
* Submits transactions to the Nullmask contract
* Pays gas fees (reimbursed from the transaction's fee allocation)
* Hides the sender's IP address and identity
The relayer never sees the transaction contents — it only forwards the opaque proof and public inputs.
### Guard
Approves or rejects deposits entering the privacy pool.
**Responsibilities:**
* Monitors pending deposits on the contract
* Screens depositing addresses using chain analysis tools
* Approves legitimate deposits (adds note commitments to the Merkle tree)
* Rejects flagged deposits (refunds the depositor)
* Publishes revocation keys with each approved deposit
### Smart Contract (Nullmask.sol)
The on-chain privacy pool. Deployed behind a UUPS proxy for upgradeability.
**Responsibilities:**
* Verifies ZK proofs using on-chain verifier contracts
* Manages the note commitment Merkle tree (LeanIMT with Poseidon2)
* Tracks spent nullifiers (note nullifiers and transaction nullifiers)
* Holds deposited funds (ETH and ERC-20 tokens)
* Executes Uniswap V2 swaps during shielded swap operations
* Maintains a key registry for receiving key registration
* Manages token whitelist
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