💵Note

A note represents some value of a particular asset attached to an owner's address (related to a shielded account) who has the authority to spend it. A user can zero or more notes in their shielded account. The asset balance of a shielded account is simply the sum of the values of all notes of that asset.

In our protocol, a Note is a tuple of multiple items:

• assetId: Identifier for the asset (ETH, WBTC, MATIC, etc.) this note represents the value of.

• value: Value or amount the note represents.

• leafIndex: The leaf index of the commitment merkle tree where this note will be inserted.

• blinding: A random blinding factor.

• rootAddress: The root address of a user having the authority to spend it.

• revoker: The chosen revoker's public key point.

 return new Note({
      assetId,
      value,
      leafIndex,
      blinding,
      rootAddress: account.rootAddress,
      revoker: tx.revoker,
    });

All the notes to ever exist have their commitments stored in a data structure called Merkle tree. This is essential for bookkeeping as will be clear in the next sections.

The so-called commitment of a note is defined Poseidon hash of:

commitment = H(assetId, owner, value)

where owner is the blinded address generated using the blinding of the note:

owner = H(rootAddress, revoker.x, revoker.y, blinding)