> ## Documentation Index
> Fetch the complete documentation index at: https://starkware-9575960b-starkzapv4.mintlify.site/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. |


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