SCPN: Simplicity Contract Propagation on Nostr

A decentralized discovery and interaction layer for Liquid Smart Contracts, powered by Nostr.

This project is a proof-of-concept building a foundational layer for smart contract interoperability on the Liquid Network. It uses the Nostr protocol as a public, censorship-resistant "bulletin board" where users can publish, discover, and interact with Simplicity smart contracts.

🚀 Project Goal

Currently, deploying a complex contract on Liquid (using Simplicity or Miniscript) is a "fire-and-forget" action. There is no standard way for other users or wallets to:

1. Discover that the contract exists.
2. Understand its spending conditions (witness data).
3. Find all the necessary components (contract hex, taproot data) to build a valid spending transaction.

This project solves the discovery problem by creating a standardized metadata format for Simplicity contracts and propagating it as a kind: 1 event on Nostr. This allows any compatible client to find and interpret these contracts, paving the way for a more open and interactive smart contract ecosystem.

🛠️ Architecture Overview

This project is built as a monorepo with two main components:

• Frontend (SvelteKit):

  • Written in SvelteKit with TypeScript and styled with Tailwind CSS.
  • Uses NDK (Nostr Dev Kit) to communicate with Nostr relays (publishing and subscribing).
  • Integrates with NIP-07 browser extensions (like Alby or nos2x) for user authentication and event signing.
  • Provides a UI for:
    1. Dynamically creating a new contract (e.g., an oracle-based vault).
    2. Publishing the contract's metadata to Nostr.
    3. Viewing a live-updating table of all contracts published with this protocol.

• Backend (Go):

  • A simple REST API built with Go and the Fiber web framework.
  • Exposes endpoints to receive contract parameters from the frontend.
  • Executes local shell scripts that wrap calls to the simc (SimplicityHL) compiler and hal-simplicity CLI.
  • This process compiles the human-readable Simplicity code into raw hex, generates the taproot address, and computes all necessary metadata (like the control block) required for spending.
  • Returns the complete contract data as a JSON object to the frontend, ready for publishing.

Prerequisites

Before you begin, ensure you have the following tools installed and configured on your system.

1. Nostr

• A Nostr Account: You need a keypair (public npub... and private nsec...).
• NIP-07 Browser Extension: This is required for logging into the web app.
  • nos2x (Recommended)
  • Alby

2. Core Dependencies

• Rust & Cargo: Required to build the Simplicity tools.

  curl --proto '=https' --tlsv1.2 -sSf [https://sh.rustup.rs](https://sh.rustup.rs) | sh
  source "$HOME/.cargo/env"

• Go (latest stable): Powers the backend API.

  • Visit the Official Go Website for installation instructions.

• Node.js (v22+): Required for the SvelteKit frontend.

  • We recommend using nvm (Node Version Manager) to manage Node versions.

  curl -o- [https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh](https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh) | bash
  export NVM_DIR="$HOME/.nvm"
  [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
  [ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion"
  
  # Install and use Node 22
  nvm install 22
  nvm use 22

🚀 Setup and Installation

Follow these steps to build the dependencies and run the project.

1. Clone the Simplicity Tools

You must compile simplicity-hl (which provides simc) and hal-simplicity from source.

# Clone and build simplicity-hl
git clone [https://github.com/BlockstreamResearch/SimplicityHL.git](https://github.com/BlockstreamResearch/SimplicityHL.git)
cd SimplicityHL
cargo build --release
# Make sure the binary is in your PATH. Example:
# sudo cp target/release/simc /usr/local/bin/

# Go back to your main projects directory
cd ..

# Clone and build hal-simplicity
git clone [https://github.com/BlockstreamResearch/hal-simplicity.git](https://github.com/BlockstreamResearch/hal-simplicity.git)
cd hal-simplicity
cargo build --release
# Make sure the binary is in your PATH. Example:
# sudo cp target/release/hal-simplicity /usr/local/bin/

# Verify that both are in your PATH
which simc
which hal-simplicity
# Both commands should return a path (e.g., /usr/local/bin/simc)

2. Clone the MareNostrum repository

git clone https://github.com/YOUR_USERNAME/YOUR_REPO_NAME.git
cd YOUR_REPO_NAME

3. Run front-end Svelte

npm install
npm run dev

4. Run back-end Go Fiber

cd backend-go
go get .
go run .

It should now be runnig everything and you can access MareNostrum at http://localhost:5173