casawybla

Bitcoin Ledger x Starknet Account — a POC that connects a Ledger hardware wallet (Bitcoin app) to deploy and control an Argent account on Starknet Sepolia.

The Ledger Bitcoin app produces secp256k1 signatures wrapped with the Bitcoin message prefix and double SHA-256. A forked Argent v0.5.0 contract adds a Bitcoin signer variant that reconstructs this format on-chain before verifying.

Architecture

contracts/   Cairo contracts (forked Argent v0.5.0 + Bitcoin signer)
webapp/      React + Vite frontend (Ledger WebHID, starknet.js)
scripts/     Deployment utilities

Quick Start

Contracts

See contracts/README.md for build/test instructions. Requires Scarb 2.10.1 and snforge 0.38.3.

Webapp

cd webapp
npm install

# (Optional) Set a custom RPC endpoint
cp .env.example .env
# Edit .env with your Dwellir/Alchemy/Blast API key

npm run dev

Open the app in a browser, connect a Ledger with the Bitcoin app open, and follow the step-by-step wizard:

1. Connect Ledger — derives a secp256k1 public key, computes the pubkey hash
2. View Account — shows the counterfactual Starknet address and balances
3. Deploy — deploys the Argent account (requires pre-funding via Sepolia faucet)
4. Transfer — sends ERC-20 tokens from the account

Multi-account support is available via the account index selector (BIP44 derivation path 44'/0'/0'/0/{i}).

How It Works

1. The Ledger Bitcoin app signs a 32-byte message (the Starknet tx hash) using signMessage, which wraps it as SHA256(SHA256("\x18Bitcoin Signed Message:\n" + varint(32) + msg))
2. The frontend normalizes the signature (low-s) and serializes it in Argent's account signature format
3. The on-chain contract reconstructs the same Bitcoin message envelope, double-SHA256s it, recovers the secp256k1 public key, and verifies it matches the stored pubkey_hash

License

MIT