# What is a note in Redacted?

A note is a sealed entry on-chain that records coins in Redacted’s Reserve and that only your keys can open. From the outside all notes look alike, whoever owns them and whatever they hold.

Also called encrypted note or private note.

## What a note is made of

Every deposit and every private action mints a note: a Poseidon commitment appended to the note tree, next to a ciphertext sealed to its owner with AES-256-GCM. The tree keeps the commitment, and the ciphertext is what lets your browser find and read your own notes.

## How a note is spent

Spending needs a zero-knowledge proof that you own an unspent note in the tree, without revealing which one. A nullifier then retires the note forever, so it can be spent only once, and the action mints fresh notes in turn.

## Why there is no database

Your account is the set of notes your keys can open, and notes are never deleted. Any browser holding your keys can rebuild your account from the chain, which serves as both the backup and the ledger, with your signature as the only index into it.

## Status

Notes are how the Reserve works today. To every observer, the relayer included, they are envelopes stacking up in a tree 4.3 billion slots deep.

More: [Architecture](https://redacted.gg/docs/protocol/architecture.md)

## Related terms

- [Commitment](https://redacted.gg/glossary/commitment.md): A commitment locks in a piece of data without revealing it. Later it can be opened and anyone can check that it matches, but until then it gives nothing away and cannot be changed.
- [Nullifier](https://redacted.gg/glossary/nullifier.md): A nullifier is a unique value published when a private note is spent. It lets the chain reject a second spend of the same note without revealing which note was spent.
- [Merkle tree](https://redacted.gg/glossary/merkle-tree.md): A Merkle tree fingerprints a long list with one short value, the root, so that anyone can prove an item is in the list with a handful of hashes instead of the whole list.
- [The Reserve](https://redacted.gg/glossary/reserve.md): The Reserve is the shared space where every Redacted user’s deposits live together as sealed notes. From the outside all notes look alike, so an action from the Reserve could have come from anyone who has the same coin in it.
- [Zero-knowledge proof](https://redacted.gg/glossary/zero-knowledge-proof.md): A zero-knowledge proof lets someone prove that a statement is true without revealing anything else, for example that they own funds and may spend them, without showing which funds or who they are.
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Page: https://redacted.gg/glossary/note/