DarkPool

Sealed prediction markets on Starknet — bet UP/DOWN on BTC/USD with positions and amounts hidden until after oracle resolution.

Built for the Starknet RE{DEFINE} Hackathon — Privacy Track

The Problem

On-chain prediction markets expose all positions publicly. This enables:

• Front-running — whales move odds, others pile on
• Herd behavior — bettors copy the visible majority instead of thinking independently
• Information leakage — market makers extract alpha from visible order flow

The Solution

DarkPool uses a Poseidon commit-reveal scheme so that both bet direction AND amount are hidden on-chain until after the oracle determines the outcome. Sealed-bid mechanisms produce more honest pricing — DarkPool applies the same principle to prediction markets.

Architecture

┌─────────────────────────────────────────────────────────────┐
│            React Frontend (Vite + Tailwind + shadcn/ui)     │
│   Wallet: ArgentX / Braavos via starknet-react              │
│   State: contract reads + localStorage for salts            │
└───────────────────────┬─────────────────────────────────────┘
                        │ starknet.js RPC
        ┌───────────────┼───────────────┐
        ▼               ▼               ▼
┌──────────────┐ ┌─────────────┐ ┌──────────────┐
│  Keeper Svc  │ │ Starknet    │ │ Pyth Hermes  │
│  (Node.js)   │ │ (Sepolia)   │ │ (BTC/USD)    │
│  - Create    │ │ - Contract  │ └──────────────┘
│  - Resolve   │ │   reads     │
│  - Finalize  │ │ - Tx submit │
└──────┬───────┘ └─────────────┘
       ▼
┌─────────────────────────────────────────────────────────────┐
│                    Starknet Sepolia                          │
│  DarkPool Contract    Pyth Oracle    STRK (ERC-20)          │
│  commit() → reveal() → claim()                              │
└─────────────────────────────────────────────────────────────┘

How It Works

Phase	Duration	What Happens
Seal	2.5 min	Users commit Poseidon hashes + fixed escrow. Bets hidden.
Closed	2.5 min	No more bets. Awaiting oracle.
Resolve	—	Keeper reads BTC/USD from Pyth, sets outcome.
Reveal	5 min	Users prove bets by submitting original inputs. Hash verified on-chain.
Finalize	—	Winners split losing pool (parimutuel). 3% fee on losers.

Privacy mechanism: commitment = poseidon(direction, amount, salt, user_address) — everyone deposits the same escrow so all on-chain commitments look identical.

Tech Stack

Layer	Technology
Contracts	Cairo 2.16.0 / Scarb 2.16.0 / Starknet Foundry 0.56.0
Contract libs	OpenZeppelin Cairo 0.20.0, Pyth Starknet
Frontend	React 19, TypeScript, Vite, Tailwind CSS 4, shadcn/ui
Wallet	starknet-react (ArgentX / Braavos)
Oracle	Pyth Network (BTC/USD pull oracle)
Keeper	Node.js + TypeScript + starknet.js 6.x
Token	STRK (ERC-20)

Project Structure

contracts/     — Cairo smart contracts (50 tests)
frontend/      — React + Tailwind + shadcn/ui web app
keeper/        — Node.js market lifecycle service
scripts/       — Deploy + utility scripts

Quick Start

Prerequisites

• Scarb 2.16.0 (Cairo build tool)
• Starknet Foundry 0.56.0 (testing)
• Node.js 22+
• ArgentX or Braavos browser wallet (Starknet Sepolia)

Contracts

cd contracts/
scarb build                # Compile Cairo contracts
snforge test               # Run all 50 tests

Frontend

cd frontend/
npm install
npm run dev                # Dev server at http://localhost:5173
npm run build              # Production build
npm test                   # Playwright E2E tests (21 tests)

Keeper

cd keeper/
npm install

# Set environment variables
export STARKNET_RPC_URL="https://starknet-sepolia.public.blastapi.io"
export KEEPER_PRIVATE_KEY="0x..."
export KEEPER_ADDRESS="0x..."
export DARKPOOL_ADDRESS="0x00dbb9c226a1d12e1f33a94b56af49b81e7ec9e7f3f405ec1940146c6e5e22ab"

npm run dev

Contract Addresses (Starknet Sepolia)

Contract	Address
DarkPool	0x00dbb9c226a1d12e1f33a94b56af49b81e7ec9e7f3f405ec1940146c6e5e22ab
STRK	0x04718f5a0fc34cc1af16a1cdee98ffb20c31f5cd61d6ab07201858f4287c938d
Pyth Oracle	0x07f2b07b6b5365e7ee055bda4c0ecabd867e6d3ee298d73aea32b027667186d6

Key Design Decisions

• Poseidon hash over Pedersen — 5x cheaper in Cairo, STARK-native
• Fixed escrow — everyone deposits the same amount so commitments look identical on-chain
• Resolve before reveal — oracle reads price before users reveal, preventing strategic non-revelation
• Parimutuel payout — winners split losing pool proportionally; 3% fee on losing side only
• Forfeiture — unrevealed escrows go to the payout pool (disincentivizes griefing)
• Client-side salt storage — no backend database needed; export/import for backup

Screenshots

Coming soon — see demo video

Testing

• Contracts: 50 unit tests covering commit, resolve, reveal, claim, edge cases
• Frontend: 21 Playwright E2E tests covering app loading, market flow, salt management, how-it-works

# Contracts
cd contracts/ && snforge test

# Frontend
cd frontend/ && npm test

License

MIT