> For AI agents: the documentation index is at https://docs.umbraprivacy.com/llms.txt, and every page is available as Markdown at its URL with .md appended.

# Glossary (/docs/resources/glossary)

Terms are in alphabetical order. Each links to the page that explains it.

**Account signature.** The one signature your main wallet makes over a fixed Umbra message. Umbra's clients derive every key in your account from it; the protocol does not require it. [Read more](https://docs.umbraprivacy.com/docs/account/account-signature)

**Anonymity set.** The technical term for the set of notes a spend cannot be told apart from. [Read more](https://docs.umbraprivacy.com/docs/privacy/anonymity-set)

**Attestation.** A document an AWS Nitro enclave produces, signed through AWS's certificate chain, that states which code image the enclave runs and what data it commits to. [Read more](https://docs.umbraprivacy.com/docs/cryptography/trusted-execution)

**Attestation marker.** The account the Nitro attestation verifier creates once it has checked an attestation document, which the registries read. [Read more](https://docs.umbraprivacy.com/docs/cryptography/trusted-execution)

**Attester.** One of the six services that must sign every value transaction: the three guardian nodes, the screener, the fee enclave and the data endorser. [Read more](https://docs.umbraprivacy.com/docs/architecture/services)

**BabyJubJub.** An elliptic curve defined over the BN254 scalar field, so signatures on it can be checked inside a circuit. Each zone's signing key is a key on this curve. [Read more](https://docs.umbraprivacy.com/docs/cryptography/signatures)

**Batch append.** The forester's proof that it inserted a batch of staged nullifiers into the nullifier tree correctly. [Read more](https://docs.umbraprivacy.com/docs/proofs/batch-append)

**Blinding factor.** A random value mixed into a commitment so the commitment reveals nothing about what it commits to. [Read more](https://docs.umbraprivacy.com/docs/cryptography/commitments)

**BLS signature.** A signature scheme on the BN254 curve in which signatures add up: the sum of several signatures verifies against the sum of the signers' keys. [Read more](https://docs.umbraprivacy.com/docs/cryptography/signatures)

**BN254.** The pairing-friendly elliptic curve Umbra's proofs and BLS signatures use, and whose scalar field all circuit values live in. [Read more](https://docs.umbraprivacy.com/docs/cryptography/security-levels)

**Bootstrap key.** A key set when a program is built, used to initialise its governance and, for some programs, as a break-glass authority. [Read more](https://docs.umbraprivacy.com/docs/security/governance)

**Circuit.** A set of arithmetic constraints that a zero-knowledge proof shows were satisfied. Umbra's circuits are written in Circom. [Read more](https://docs.umbraprivacy.com/docs/proofs/overview)

**Cluster.** A group of guardian nodes registered together, with one aggregate BLS key. [Read more](https://docs.umbraprivacy.com/docs/guardian-nodes#who-controls-the-cluster)

**Combined attester signature.** The one BLS signature a value transaction carries, made by adding the six attesters' signatures together. [Read more](https://docs.umbraprivacy.com/docs/architecture/overview)

**Commitment.** A value that fixes some data without revealing it. A note commitment fixes a note's thirteen fields. [Read more](https://docs.umbraprivacy.com/docs/state/commitments)

**Context digest.** A Keccak-256 hash of a transaction's payload, up to the combined attester signature, and of every account it names, the submitter's included. The attesters sign it and the proof commits to it, which binds them to one exact transaction. [Read more](https://docs.umbraprivacy.com/docs/fees/relayers)

**Context service.** The indexer's service that returns Merkle paths, nullifier gaps and payee resolution for a spend. [Read more](https://docs.umbraprivacy.com/docs/privacy/metadata)

**Data endorser.** The attester that checks a transaction's encrypted notes match what the transaction commits to, archives them and signs. [Read more](https://docs.umbraprivacy.com/docs/architecture/services)

**Degraded.** A cluster status: a member is down or runs an unapproved image. The pool refuses transactions while the cluster is Degraded. [Read more](https://docs.umbraprivacy.com/docs/guardian-nodes#who-controls-the-cluster)

**Deposit.** Moving tokens from a public account into the pool, receiving notes for them. [Read more](https://docs.umbraprivacy.com/docs/operations/deposit)

**Disclosure section.** Part of a transaction's private data that lets a holder of the sender's viewing key open selected fields to a zone authority. [Read more](https://docs.umbraprivacy.com/docs/disclosure)

**Domain separation.** Giving each kind of object its own tag in its hash, so two different kinds can never produce the same value. [Read more](https://docs.umbraprivacy.com/docs/cryptography/hashing)

**Dummy note.** A note with amount zero that fills an unused slot so every transaction has the same shape. [Read more](https://docs.umbraprivacy.com/docs/state/notes)

**Encrypted note.** A note's contents encrypted to its owner with ML-KEM-768 and AES-256-GCM, stored off chain. [Read more](https://docs.umbraprivacy.com/docs/cryptography/encryption)

**Escape hatch.** A way to withdraw one note with no attester, at the cost of disclosing that note. [Read more](https://docs.umbraprivacy.com/docs/operations/escape-hatch)

**Execution slot.** The slot a transaction's proof was made for. The program refuses a proof whose execution slot is too old. [Read more](https://docs.umbraprivacy.com/docs/state/notes)

**Fee commitment.** A commitment to one protocol fee payment. Every value transaction appends three. [Read more](https://docs.umbraprivacy.com/docs/fees/fee-model)

**Fee enclave.** The attester, running in a Nitro enclave, that checks a transaction's fee notes and signs. [Read more](https://docs.umbraprivacy.com/docs/fees/fee-enclave)

**Fee voucher.** A commitment to the fee reductions the fee enclave applied to a transaction. [Read more](https://docs.umbraprivacy.com/docs/fees/fee-model)

**Forester.** A service, which anyone may run, that inserts staged nullifiers into the nullifier tree. [Read more](https://docs.umbraprivacy.com/docs/state/forester)

**Freshness proof.** A transaction's second proof, that its nullifiers are not yet in the nullifier tree. [Read more](https://docs.umbraprivacy.com/docs/proofs/nullifier-freshness)

**Frontier.** The right edge of an append-only Merkle tree: all a program needs to keep to append leaves and compute the root. [Read more](https://docs.umbraprivacy.com/docs/state/note-tree)

**Funded-by field.** A note field that records the sender's identity commitment when the transaction spent an identity-owned note of the same token. [Read more](https://docs.umbraprivacy.com/docs/state/notes)

**Groth16.** The zero-knowledge proof system Umbra uses: small proofs, cheap verification, and a trusted setup per circuit. [Read more](https://docs.umbraprivacy.com/docs/cryptography/zero-knowledge-proofs)

**Guardian node.** One of three Nitro-enclave services that co-sign every registration and value transaction and hold one share of each viewing key. [Read more](https://docs.umbraprivacy.com/docs/guardian-nodes)

**Identity commitment.** Your on-chain identity: one value that commits to your keys, your platform wallet and your encryption key, sometimes called the user commitment. [Read more](https://docs.umbraprivacy.com/docs/account/identity)

**Identity tree.** The shielded pool's tree of registered identity commitments. [Read more](https://docs.umbraprivacy.com/docs/state/trees)

**Indexed tree.** A Merkle tree whose leaves form a sorted linked list, so a value's absence can be proved. [Read more](https://docs.umbraprivacy.com/docs/cryptography/merkle-trees)

**Indexer.** The service that mirrors the chain's trees, archives encrypted notes and serves paths and notes. [Read more](https://docs.umbraprivacy.com/docs/architecture/services)

**Lamport account.** The one account, owned by the shielded pool program and shared by every pool index, that holds the SOL behind every SOL note as plain lamports. The code calls it `LamportVault`. [Read more](https://docs.umbraprivacy.com/docs/state/tokens#sol)

**Lane.** A deposit or withdrawal slot in a value transaction. Each transaction has two of each. [Read more](https://docs.umbraprivacy.com/docs/proofs/transaction-circuit)

**Main wallet.** Your own Solana wallet. [Read more](https://docs.umbraprivacy.com/docs/account/overview)

**Measurement.** A hash of an enclave's code image. A registry accepts an enclave only on an approved measurement. [Read more](https://docs.umbraprivacy.com/docs/cryptography/trusted-execution)

**Memo digest.** A Keccak-256 hash that binds a transaction to its off-chain encrypted notes. [Read more](https://docs.umbraprivacy.com/docs/operations/receive-and-sync)

**Merkle tree.** A tree of hashes whose root commits to every leaf, so a short path proves a leaf is in it. [Read more](https://docs.umbraprivacy.com/docs/cryptography/merkle-trees)

**ML-KEM-768.** A post-quantum key encapsulation standard (FIPS 203). Umbra encrypts notes with it. [Read more](https://docs.umbraprivacy.com/docs/cryptography/encryption)

**Note.** The unit of private balance: an amount of one token, owned by one identity or one Solana address. [Read more](https://docs.umbraprivacy.com/docs/state/notes)

**Nullifier.** A value a spend publishes to mark a note spent, which cannot be tied to the note without its owner's key. [Read more](https://docs.umbraprivacy.com/docs/state/nullifiers)

**Nullifier key.** The key that turns your notes into their nullifiers. [Read more](https://docs.umbraprivacy.com/docs/account/keys)

**Outgoing viewing key.** The key that derives every per-transaction viewing key and opens your sender records. [Read more](https://docs.umbraprivacy.com/docs/account/keys)

**Pass-through.** A movement of value from a deposit lane straight to a withdrawal lane. [Read more](https://docs.umbraprivacy.com/docs/fees/fee-model)

**Per-transaction viewing key.** A key derived for one transaction from your outgoing viewing key, which encrypts that transaction's sender record. [Read more](https://docs.umbraprivacy.com/docs/account/keys)

**Platform wallet.** A Solana keypair Umbra's clients derive from your account signature, committed in your identity and used as the depositor on deposits. [Read more](https://docs.umbraprivacy.com/docs/account/platform-wallet)

**Pool index.** The number of one set of trees and staging buffers. The pool can run several. [Read more](https://docs.umbraprivacy.com/docs/state/note-tree)

**Pool token account.** A token account, owned by the pool's program-derived authority, that holds one token's pooled balance. SOL has none; it sits in the lamport account. [Read more](https://docs.umbraprivacy.com/docs/state/tokens)

**Poseidon.** A hash function designed to be cheap inside circuits. Umbra uses it for commitments, nullifiers and trees. [Read more](https://docs.umbraprivacy.com/docs/cryptography/hashing)

**Privacy artifacts root.** One value that commits to a transaction's encrypted sender record, its per-lane commitments, the guardian nodes' viewing-key share leaves and the disclosure sections. The proof, the guardian nodes and the data endorser all check against it. [Read more](https://docs.umbraprivacy.com/docs/proofs/transaction-circuit)

**Private balance.** What you hold in Umbra: the sum of your unspent notes. [Read more](https://docs.umbraprivacy.com/docs/account/overview)

**Private Send.** The product name for a private transfer. [Read more](https://docs.umbraprivacy.com/docs/operations/private-send)

**Program-owned note.** A note owned by a Solana address, such as a program, rather than by an identity. [Read more](https://docs.umbraprivacy.com/docs/state/notes)

**Proof of possession.** A signature over a BLS key by that key, which stops anyone registering a key they do not control. [Read more](https://docs.umbraprivacy.com/docs/cryptography/signatures)

**QuorumOS.** The enclave operating system, built by Turnkey, that the guardian nodes and other enclaves run under. It manages each enclave's quorum key, which is split among that enclave's quorum members. [Read more](https://docs.umbraprivacy.com/docs/guardian-nodes)

**Recent-root window.** The most recent roots of a tree, any of which a proof may name: 512 for the note, identity and fee commitment trees. [Read more](https://docs.umbraprivacy.com/docs/state/note-tree)

**Registration.** Publishing your identity commitment in the identity tree. [Read more](https://docs.umbraprivacy.com/docs/operations/register)

**Relayer.** A service that submits a transaction for you and pays its Solana fee. The code calls it the submitter. [Read more](https://docs.umbraprivacy.com/docs/fees/relayers)

**Screener.** The attester that screens every value transaction's submitter and the public counterparties of its deposits and withdrawals. [Read more](https://docs.umbraprivacy.com/docs/screening)

**Sender record.** An encrypted record of a transaction's inputs and outputs, readable with its per-transaction viewing key. [Read more](https://docs.umbraprivacy.com/docs/disclosure)

**Shamir secret sharing.** Splitting a value into shares so that any two of three reconstruct it and one reveals nothing. [Read more](https://docs.umbraprivacy.com/docs/cryptography/secret-sharing)

**Shielded pool.** The Solana program that holds pooled tokens and settles every operation. [Read more](https://docs.umbraprivacy.com/docs/architecture/programs)

**Staging buffer.** The account where a transaction's nullifiers wait until the forester inserts them; the code calls it the turnstile. [Read more](https://docs.umbraprivacy.com/docs/state/double-spend)

**Trusted setup.** The ceremony that makes a Groth16 circuit's keys, sound if at least one participant was honest. [Read more](https://docs.umbraprivacy.com/docs/security/trusted-setup)

**Turnkey Verifiable Cloud (TVC).** Turnkey's service for running enclave applications under QuorumOS. The guardian nodes run on it. [Read more](https://docs.umbraprivacy.com/docs/guardian-nodes)

**Validity window.** The slots between which a note may be spent. [Read more](https://docs.umbraprivacy.com/docs/state/notes)

**View tag.** Four bytes at the front of an encrypted note that let a wallet skip decrypting most notes not meant for it. [Read more](https://docs.umbraprivacy.com/docs/operations/receive-and-sync)

**Withdraw.** Moving tokens out of the pool to a public account. [Read more](https://docs.umbraprivacy.com/docs/operations/withdraw)

**Zero-knowledge proof.** A proof that a statement is true which reveals nothing beyond that. [Read more](https://docs.umbraprivacy.com/docs/cryptography/zero-knowledge-proofs)

**Zone.** A numbered domain whose signing key must approve transactions moving notes into or out of it. Zone 0 means no zone. [Read more](https://docs.umbraprivacy.com/docs/zones)

**Zone authority.** The key that manages a zone in the zone registry; a separate signing key signs its transactions. [Read more](https://docs.umbraprivacy.com/docs/zones)


Last updated 12 October 2026