> For the complete documentation index, see [llms.txt](https://void-protocol-2.gitbook.io/void-protocol-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://void-protocol-2.gitbook.io/void-protocol-docs/privacy/notes-commitments-roots-nullifiers.md).

# Notes, Commitments, Roots, and Nullifiers

## Privacy Concepts

### Note

A **note** is a private record of value containing:

* token
* amount
* owner key
* nullifier secret
* random blinding value

Amounts are stored as **64-bit numbers**.

The testnet VOID token uses **6 decimals**, so a single note can hold approximately **18.4 trillion tokens**.

That is far above the planned **1 billion VOID mainnet supply**.

{% hint style="info" %}
In practice, there is **no meaningful per-note limit for VOID**.
{% endhint %}

### Commitment

A **commitment** is a cryptographic commitment to a note that is published on-chain.

It proves that the note exists without revealing the note contents by itself.

### Merkle Root

All commitments are stored inside a **Merkle tree**.

A zero-knowledge proof can show:

> “My note exists in this tree under this root.”

without revealing which specific note is being spent.

### Nullifier

A **nullifier** is computed from the note's nullifier secret and its position (leaf index) in the Merkle tree, and is published when the note is spent:

`nullifier = Poseidon2(nullifierSecret, leafIndex)`

The circuits also check that the Merkle path used in the proof matches the same leaf index.

Each nullifier can appear only once.

This prevents the same note from being spent twice.

{% hint style="info" %}
A nullifier is designed not to reveal which published commitment it corresponds to.
{% endhint %}

{% hint style="warning" %}
**Known limitation:** whoever creates a note chooses its nullifier secret. A sender who creates a note for you can therefore potentially recognise when that particular note is later spent. Recipient-private nullifier derivation is planned and needs a separately reviewed design.
{% endhint %}

### Association Set Root

VOID is designed to support **association sets**.

An association set is a published set of approved deposits that can be used to prove that funds originate from an approved set without revealing which specific deposit they came from.

{% hint style="warning" %}
**Association-set enforcement is not live today.**

Selective disclosure is also not currently available.
{% endhint %}

A spend can reference a published association root, but the current circuits do **not yet verify** that the spent note belongs to that set.

The association root currently published on testnet is a **placeholder**.

#### Registry Control

The association registry is owned by the **2-of-3 Safe**.

The Safe can:

* publish roots
* revoke roots

{% hint style="info" %}
Association-set enforcement is planned for a later production stage and will require circuit-level verification.
{% endhint %}

### Encrypted Note Storage

Notes are stored **encrypted in your browser** and unlocked using a wallet signature.

Notes sent to you are encrypted to your key so that only you can read them.

<table data-view="cards"><thead><tr><th></th><th></th></tr></thead><tbody><tr><td><strong>Storage</strong></td><td>Encrypted locally in the browser.</td></tr><tr><td><strong>Unlock</strong></td><td>Uses a wallet signature.</td></tr><tr><td><strong>Incoming Notes</strong></td><td>Encrypted so only the intended recipient can read them.</td></tr></tbody></table>

{% hint style="warning" %}
Note backup and recovery are not currently live.

If you permanently lose access to the wallet used to unlock your private balance, you may also lose access to those notes.
{% endhint %}


---

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