Polkadot Block Header Light Client

This project implements a Polkadot block header light client, which listens to new Polkadot headers and stores sequential batches of them inside a Merkle tree. It fulfills the following attributes:

Decides on a header batch size and creates and writes to Merkle tree once the size limit has been reached.
Stores the Merkle trees and corresponding roots in-memory.
Allows each header to be queryable by block number or hash.
Implements functions that generate the Merkle inclusion proof for each stored header.
Implements a function for verifying the generated proofs.

Prerequisites

Make sure you have installed all of the following prerequisites on your development machine:

Node.js
Typescript
@polkadot/api package

Getting Started

Clone the repository and install the dependencies:

git clone https://github.com/Zeusmist/polkadot-block-header-client.git
cd polkadot-block-header-client
npm install

Running the client

npm start

Querying Headers

You can query a block header by its number or hash using the following methods:

queryByBlockNumber(blockNumber: number): BlockHeader | null
queryByHash(hash: string): BlockHeader | null

Generating and Verifying Proofs

You can generate a Merkle proof for a specific header by block number or hash and verify it using the following methods:

generateProofByBlockNumber(blockNumber: number): Buffer[] | null
generateProofByHash(hash: string): Buffer[] | null
verifyProof(leaf: Buffer, proof: Buffer[]): boolean

Tests

To run the test suite, execute:

npm test

Code Structure

src\models\Batch.ts: Contains the Batch class to manage a batch of headers and the corresponding Merkle tree.
src\models\BlockHeader.ts: Defines the BlockHeader interface.
src\models\MerkleTreeModel.ts: Wraps the Merkle tree functionality.
src\PolkadotClient.ts: Implements the Polkadot client, including listening to new headers, batching them, and query functionality.
src\tests\PolkadotClient.test.ts: Contains the tests for the PolkadotClient class.