> ## Documentation Index
> Fetch the complete documentation index at: https://docs.starknet.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Glossary

> Terms used across Starknet Privacy documentation

| Term                   | Meaning                                                                                                                                                                        |
| ---------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Privacy pool**       | Smart contract holding pooled ERC-20s and enforcing proofs + write-once state.                                                                                                 |
| **Note**               | Immutable record of ownership of an amount of a token; spent via **nullifier**.                                                                                                |
| **Nullifier**          | One-time value revealed when spending a note; prevents double-spend; unlinkable without viewing key.                                                                           |
| **Channel**            | Unidirectional link sender → recipient; first send opens it and shares **channel key** (encrypted to recipient).                                                               |
| **Channel key**        | Shared secret derived from sender/recipient viewing material; indexes note locations.                                                                                          |
| **Subchannel**         | Per-channel, per-token lane for notes (avoids extra channel opens per asset).                                                                                                  |
| **Viewing key**        | Key pair: private (k) for decrypt/trace/nullifier; public (K) for encrypt-to-user.                                                                                             |
| **Client-side action** | High-level user intent (open channel, use note, withdraw, …).                                                                                                                  |
| **Server-side action** | Primitive the contract runs (WriteOnce, append channel, ERC-20 transfer).                                                                                                      |
| **WriteOnce**          | Storage write only if cell is zero—immutability.                                                                                                                               |
| **Open note**          | Note whose encoding uses a reserved salt so the filled amount is **plaintext** on-chain; used when an external contract must set the amount after the proof (e.g. AMM output). |
| **Paymaster**          | Relayer that submits txs and is reimbursed from the pool.                                                                                                                      |
| **Auditing entity**    | Holder of k\_audit; decrypts escrowed viewing keys under compliance process.                                                                                                   |
| **Stwo**               | STARK prover used for client-side Cairo proofs.                                                                                                                                |