Glossary
Every term these docs and the SDK use, in one or two plain sentences.
Terms are in alphabetical order. Each has its own link, so you can point to it from your own docs. The protocol glossary goes deeper.
Account signature
The one message a user's wallet signs to open their private account. Every key of the account is derived from it, so the SDK treats it as a secret.
Commitment
A value that fixes some data without revealing it. Each new note's commitment is published on
chain, while the note itself stays encrypted. The commitment option is something else: Solana's
confirmation level.
Committee
The services that check and sign every payment before the pool accepts it: the guardian nodes, the screener, the fee enclave and the data endorser. Their signatures are combined into one.
Context
The object a payment runs in, made from a session by createDepositContext and its siblings. It
picks the pool and the committee nodes the payment uses.
Coordinator
A service that can make a payment's requests to the committee and the relayer on the browser's
behalf. The SDK uses it only with route: "coordinator".
Deposit
Moving tokens from a user's wallet into a private balance, theirs or another user's.
Gateway token
The token that lets your app use Nimbus's services on mainnet. A session sends it to the gateway's services and nowhere else. To get one, email dev@umbraprivacy.com or reach out to any Umbra team member.
Identity
A user's registered entry in the pool: one value that commits to their keys and their platform wallet. Registering publishes it.
Indexer
The service a sync reads new notes and spends from.
Intent
The device's record of a payment it has started. These docs call it a payment in progress. It stays until the payment lands or can no longer land.
Lease
The hold a payment in progress puts on the notes it spends, so no other payment spends them too.
Leased notes count as reserved.
Merge
A Private Send to the user's own account that combines several notes into one. The SDK runs merges first when the three largest notes cannot cover a payment.
Note
The unit of a private balance: an amount of one token, owned by one private account. A private balance is the sum of its unspent notes.
Nullifier
A value a payment publishes to mark a note spent. Nobody can tell which note it marks without the owner's keys.
Pending
Funds paid to a user that cannot be spent yet. A new deposit is pending until Solana finalizes it.
Platform wallet
A second Solana address the SDK derives from the account signature. Registration binds it to the user's wallet, and deposits pass through it.
Pool
The Solana program that holds every deposited token, under the rules it enforces. Pools are numbered, and the SDK uses the highest open one by default.
Private account
Everything a user holds in Nimbus. The account signature unlocks it on a device.
Private balance
What a user holds in Nimbus, kept on their device. The SDK reads it with readBalances.
Private Send
A payment from one private balance to another. The chain shows neither the sender, the recipient, nor the amount.
Proof
A zero-knowledge proof the device builds for each registration and payment. It shows the payment follows the pool's rules without revealing its private details.
Proving keys
The large circuit files the device needs to build proofs. The SDK downloads them once, checks each one's SHA-256, and caches them.
Registration
The one Solana transaction a wallet sends before its first deposit. It publishes the user's identity in the pool.
Relayer
A service that submits withdrawals and Private Sends to Solana and pays their network fee. The user's wallet signs neither.
Reserved
Funds held by a payment in progress. They come back once the payment can no longer land, or when
releaseReservedNotes frees them.
Seed
The 64-byte secret the SDK derives from the account signature. Every key of the private account comes from it, and closing the session zeroes it.
Session
A private account opened on this device by openNimbusSession. It holds the user's keys in memory
until closeNimbusSession.
Settlement
Where a relayed payment ended up: landed, failed, pending or not-followed. By default the
SDK follows each payment until it lands.
Sync
Reading the chain and the indexer into the device, so its private balance is current. Only a sync
changes what readBalances returns.
Transaction version
The Solana transaction format a wallet signs. Payments use version 1 by default, and version 0 for wallets that cannot sign version 1.
Withdraw
Moving tokens from a private balance to any Solana address.
Zone
A numbered group of notes whose own signer must approve payments into or out of it. Zone 0 has no signer, and every payment uses it by default.
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