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Polkadot Light Client in C++

  • Team Name: Equilibrium
  • Payment Address: 0x4126272BA14F7a124b1B98633678e0e5F87Ec478
  • Level: 2

Project Overview πŸ“„β€‹

This project is to create a C++ implementation of a Light Client for Substrate-based chains. On a high level, the C++ Light Client will allow users (via JSON-RPC) to:

  • Query chain state within the client (on synced chain state, including runtime code)
  • Route user transactions to peers and track results

Project Details​

We will deliver a detailed specification of a light client for the implementation based on the research done in the time frame specified in this proposal. The actual implementation will be performed in the next phase.

The specification includes:


Define primitives / library requirements such as blake2 hashing for proof verification
Check library availabilities and provide estimates for missing libraries

Embedding Runtime​

Define runtime environment requirements (Browser / NodeJS application / Other?)*
Select runtimes such as wasmedge and/or emscripten cross-compilation for desktop / server and/or browser
Define embedding environment interface such as bindings in JavaScript

Specifications for multichain support​

Specify scope and support for Parachain and Relay chain

JSON-RPC service APIs​

Define APIs to be supported* (submitting transactions, watching transactions / blocks / accounts, etc)

As the RPC API is currently unstable (see PSPs#41), specification must be written first.

Components specifications / selection​

Networking (likely cpp-libp2p)
Database (likely SQLite)

*Web3 Foundation input required

Ecosystem Fit​

This is an alternate implementation to the WASM light node in Smoldot.

Team πŸ‘₯​

Team members​

  • Vaclav Barta
  • Mark Henderson


  • Registered Address: LeipΓ€tehdas, Kaikukatu 4, 6th floor 00530 Helsinki, Finland
  • Registered Legal Entity: Equilibrium Group Oy

Team's experience​

  • Vaclav Barta is a Senior Software Developer at Equilibrium. Having implemented C++ projects for companies from Akamai to Deutsche Bank, currently creating smart contract pipelines from C to WebAssembly for XRPL Foundation.
  • Mark Henderson is the VP of Engineering at Equilibrium. He has led the team starting with the original Rust IPFS grant in late 2019, through engagements with many of the largest names in Web3, and is now circling back to finish the critical work the team started with the original Ziggurat proposal. Core contributor to OrbitDB, Rust IPFS, and Ziggurat.

Team Code Repos​

Development Status πŸ“–β€‹

Equilibrium discussed with David Hawig on different implementation on Polkadot host, C++, AssemblyScript and Zig. After initial research, Equilibrium has decided to apply for the C++ implementation of the light node.

Development Roadmap πŸ”©β€‹

To achieve the final implementation, the project is broken down into 2 phases:

  • Phase 0: Initial research for C++ Light Client specification
  • Phase 1: Light Client implementation

This proposal is only for Phase 0 and will culminate with the delivery of a detailed specification for the light client implementation in Phase 1.


  • Total Estimated Duration: 5 weeks
  • Full-Time Equivalent (FTE): 1
  • Total Costs: $34000 USD

Milestone 1 β€” Substrate Module Research​

  • Estimated duration: 5 weeks
  • FTE: 1
  • Costs: $34000 USD
0a.LicenseApache 2.0 / MIT
0b.FormatMarkdown (mdBook)
0c.PublishedGitHub, GitHub Pages
1.Cryptographysecurity advantages over connecting to 3rd-party node, limitations compared to full client
2.Runtime environment requirementsfor browser and Node.js
3.JSON-RPC APIsminimal run-time access interface
4.Dependencieslibraries for cryptography, networking, build

Future Plans​

From here we would move on to the implementation of the light client node in Phase 1. We expect Phase 1 to be completed by a larger team at Equilibrium.