Glossary

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.