Core concepts
This page defines the vocabulary used throughout the rest of the docs. The definitions here are deliberately conceptual — the cryptography section covers the exact constructions (hash preimages, curves, proof system) in detail.
The pool
Shielded pool : The private ledger at the heart of Armada. Value inside is held as cryptographic commitments, not public balances, so amounts and ownership stay hidden while the pool stays verifiable. There is one shared pool — which is what gives participants a larger crowd to blend into.
Shield : Moving value into the pool — deposit public USDC, receive a private balance.
Unshield : Moving value out — prove ownership of a private balance and withdraw public USDC to an address you choose.
Shielded transfer : Moving value between participants inside the pool, with no public trace of sender, recipient, or amount.
Private balances
Note : The basic unit of private value — the pool's equivalent of a coin or UTXO. It records "this much of this token belongs to this owner," visible only to the owner (and anyone holding their viewing key). Spending a note consumes it and creates new notes.
Commitment : A note's public on-chain fingerprint, and what the pool actually stores. It reveals nothing about owner or amount, but lets the protocol prove the note exists and is unaltered.
Nullifier : A one-time "spent" marker published when a note is consumed. It blocks double-spends but cannot be linked back to the note it retires, so spending stays private.
Commitment tree (Merkle tree) : An append-only tree of every commitment. To spend a note you prove its commitment is a leaf — proving membership without revealing which leaf is yours.
Keys and addresses
Armada separates the ability to spend funds from the ability to see them, so visibility can be shared without handing over control.
Spending key : The private key that authorizes spending. Whoever holds it controls the funds.
Viewing key : A separate key that lets its holder detect and decrypt your notes — incoming and outgoing — and see when they are spent, giving full read access to your history and balance without power to spend. A shareable viewing key grants that read-only visibility to an auditor or counterparty. Sharing is permanent: it cannot be revoked, and it covers all past and future activity at that address.
Nullifying key : The key material used to derive a note's nullifier, tying the "spent" marker to the spender without exposing the note.
Address (0zk address) : The identifier others use to send you shielded value. It encodes the public halves of your keys, so a sender can create a note only you can claim.
Note key (npk) : A per-note public key derived from the recipient's address; it binds a note to its intended recipient. It appears often because it is how a transaction commits to where value is going.
Cross-chain plumbing
Hub chain : The chain hosting the shielded pool and all private state — commitment tree, nullifiers, yield, fees, and governance.
Client chain : Any other supported chain. It runs only a thin bridge that moves USDC to and from the hub, and holds no private state.
CCTP : Circle's Cross-Chain Transfer Protocol, a burn-and-mint mechanism for moving native USDC between chains. Armada uses it to carry USDC between client chains and the hub.
Relayer : A service that submits your transactions and can pay gas for you. Beyond convenience this is a privacy mechanism: relaying keeps your own funded, public address off the transaction. It ferries the message but cannot read or alter the private contents.
On-chain machinery
Zero-knowledge proof : A proof that a transaction follows every rule — the spender owns the notes, amounts balance, nothing is double-spent — while revealing none of the details. Armada uses succinct proofs that are cheap to verify on-chain.
Adapter : An authorized contract that bridges shielded funds to an external protocol (such as the yield vault) and back in a single proven transaction, so value can leave and re-enter without breaking privacy. Governance authorizes each adapter.
Shielded yield / ayUSDC : Earning on shielded USDC. It is put to work in an integrated vault that issues yield-bearing shares (ayUSDC), themselves held privately — so you earn without revealing your position.
ARM token : Armada's protocol token. Holding ARM is an ownership stake in the protocol: it carries control over parameters, the treasury, upgrades, and the wind-down decision, and it is the basis for a holder's claim on protocol value — through treasury distributions, buybacks, or wind-down redemption. See the ARM token and governance sections.