Notes (Encrypted UTXOs)

A note is a private UTXO: an amount of one token owned by one inbox key. Only its commitment is public.

Fields

Field	Meaning
`owner_hash`	Owner’s inbox-key hash (`rkHash`)
`rkTrapdoor`	Randomness that blinds the owner
`value`	Amount, in token base units
`coinId`	Token address. `0x0` for native ETH.
`valueTrapdoor`	Randomness that blinds the value
`nullifiersHash`	Hash of the nullifiers spent to create this note

Commitment

rkCommitment    = Poseidon2(rkHash, rkTrapdoor)
valueCommitment = Poseidon2(value, coinId, valueTrapdoor)
noteCommitment  = Poseidon2(rkCommitment, valueCommitment, nullifiersHash)

The commitment is inserted into the note tree and emitted in NoteAdded(index, noteCommitment, noteCiphertext). nullifiersHash makes every commitment unique. Two notes with the same owner, value and trapdoors still differ, because they come from different spends. This prevents the Faerie Gold attack, where a sender creates two identical notes and only one can ever be spent.

Special cases

Deposit notes
Swap output notes

Created by the contract on approval:

rkTrapdoor = 0
valueTrapdoor = revocationPublicKeyHash from the gatekeeper
nullifiersHash = depositIndex, which is unique per deposit

The deposit is public anyway, so the ciphertext body is written in the clear.

The swap output amount is only known after the router executes. The circuit commits the owner (receivingKeyCommitment). The contract completes the note with the actual amountOut, the output token and valueTrapdoor = 0.

Lifecycle

A note is never deleted. Spending only records its nullifier.

Protocol Specification

Circuits

Notes (Encrypted UTXOs)

Fields

Commitment

Special cases

Lifecycle

​Fields

​Commitment

​Special cases

​Lifecycle

Fields

Commitment

Special cases

Lifecycle