Proving Historic State

This guide shows you how to prove historical state transitions and note inclusion using Aztec's Archive tree.

Prerequisites

• An Aztec contract project set up with aztec-nr dependency
• Understanding of Aztec's note and nullifier system
• Knowledge of Merkle tree concepts

Understand what you can prove

You can create proofs for these elements at any past block height:

• Note inclusion/exclusion
• Nullifier inclusion/exclusion
• Note validity (included and not nullified)
• Public value existence
• Contract deployment

Use cases include:

• Timestamp verification in private contexts
• Eligibility verification based on historical note ownership
• Item ownership verification
• Public data existence proofs
• Contract deployment verification

Historical Proofs

Prove state at any past block using the Archive tree. Useful for timestamps, eligibility checks, and ownership verification.

Retrieve notes for proofs

use aztec::note::note_getter_options::NoteGetterOptions;

let options = NoteGetterOptions::new();
let notes = storage.notes.at(owner).get_notes(options);

// Access first note as retrieved_note
let retrieved_note = notes.get(0);

Prove note inclusion

use dep::aztec::history::note_validity::ProveNoteValidity;

// Get block header for historical proof
let header = context.get_block_header();

// Prove note existed and wasn't nullified
// Requires: RetrievedNote, storage_slot, context
header.prove_note_validity(retrieved_note, storage_slot, &mut context);

tip

Use prove_note_validity to verify both inclusion and non-nullification in one call.

Prove nullifier inclusion

use dep::aztec::history::nullifier_inclusion::ProveNullifierInclusion;
use dep::aztec::protocol_types::hash::compute_siloed_nullifier;

// Compute nullifier (requires note hash)
let nullifier = note.compute_nullifier(&mut context, note_hash_for_nullify);
let siloed_nullifier = compute_siloed_nullifier(context.this_address(), nullifier);

// Prove nullifier was included
context.get_block_header().prove_nullifier_inclusion(siloed_nullifier);

Additional Proofs

Other available proofs:

• Note inclusion without validity check
• Nullifier non-inclusion (prove something wasn't nullified)
• Public data inclusion at historical blocks