Merkle Pallet

The Merkle pallet provides functionality for making and managing the Merkle trees.

• Config
• Call
• Pallet

Overview

The Merkle pallet provides functions for:

• Creating Merkle trees.
• Adding the manager and setting whether the manager is required.
• Adding leaf data to the Merkle tree.
• Adding nullifiers to the storage.
• Managing start/stop flags.
• Caching Merkle tree states.
• Verifying regular and zero-knowledge membership proofs

Terminology

• Membership proof in zero-knowledge: Proving that leaf is inside the tree without revealing which leaf you are proving over.

• Proof of creation in zero-knowledge: Each leaf is made with an arithmetic circuit which includes hashing several values. Proving to know all these values are called proof of creation.

• Nullifier: Nullifier is a part of this leaf circuit and is revealed when proving membership in zero-knowledge. The nullifier's role is to prevent double-spending.

Implementations

The Merkle pallet provides implementations for the following traits:

• Group Functions for creating and managing the group.

Interface

Dispatchable functions

• create_group - Create Merkle tree and their respective manager account.
• set_manager_required - Set whether manager is required to add members and nullifiers.
• set_manager - Set manager account id. Can only be called by the root or the current manager.
• set_stopped - Sets stopped storage flag. This flag by itself doesn't do anything. It's up to higher-level pallets to make appropriate use of it. Can only be called by the root or the manager;
• add_members Adds an array of leaves to the tree. Can only be called by the manager if the manager is required.
• verify - Verifies the membership proof.

Usage

The following examples show how to use the Merkle pallet in your custom pallet.

use pallet_merkle::traits::Group;
pub trait Config: frame_system::Config + pallet_merkle::Config {
	type Group: Group<Self::AccountId, Self::BlockNumber, Self::GroupId>;
}