@rolly-dev/wasm-signer

Client-side Poseidon2 hashing and bet authentication for the Rolly ZK-Rollup casino.

Built with Rust → WebAssembly (via wasm-pack), using the same Poseidon2 hasher and Goldilocks field as the plonky2 proving circuit.

Build

# requires: cargo, wasm-pack
npm run build
# → dist/node/  (Node.js, CJS, sync init)
# → dist/web/   (Browser, ESM, async init)

Usage

Node.js (CommonJS)

const {
  poseidon2_hash,
  derive_session_key,
  session_public_key,
  create_bet_auth,
} = require('@rolly-dev/wasm-signer');

const hash = poseidon2_hash(BigUint64Array.from([1n, 2n, 3n]));
// → BigUint64Array(4)

Node.js (ESM)

import {
  poseidon2_hash,
  derive_session_key,
  create_bet_auth,
} from '@rolly-dev/wasm-signer';

const hash = poseidon2_hash(BigUint64Array.from([1n, 2n, 3n]));

React

import { useRollyWasm } from '@rolly-dev/wasm-signer/react';

function BetButton({ sessionKey, amount, nonce }) {
  const { ready, create_bet_auth } = useRollyWasm();

  if (!ready) return <span>Loading...</span>;

  const handleBet = () => {
    const auth = create_bet_auth(sessionKey, BigInt(amount), BigInt(nonce));
    // send auth to server...
  };

  return <button onClick={handleBet}>Place Bet</button>;
}

Browser (vanilla ESM)

<script type="module">
  import { init, poseidon2_hash } from '@rolly-dev/wasm-signer';

  await init();  // loads .wasm, must be called once
  const h = poseidon2_hash(BigUint64Array.from([1n, 2n]));
</script>

Manual init (advanced)

import init, { poseidon2_hash } from '@rolly-dev/wasm-signer/init';

// custom wasm URL or ArrayBuffer
await init('/assets/rolly_wasm_signer_bg.wasm');
poseidon2_hash(BigUint64Array.from([1n]));

API

| Function | Input | Output | Description | |----------------------------|--------------------------------|-------------------|------------------------------------------------| | poseidon2_hash | BigUint64Array | BigUint64Array(4) | Hash N field elements | | poseidon2_two_to_one | BigUint64Array(4) × 2 | BigUint64Array(4) | Merkle hash: H(left‖right) | | derive_session_key | Uint8Array(32) | BigUint64Array(4) | MetaMask sig → session key | | session_public_key | BigUint64Array(4) | BigUint64Array(4) | session_pk = H(session_key) | | create_bet_auth | (BigUint64Array(4), bigint, bigint) | BigUint64Array(4) | MAC = H(sk‖amount_lo‖amount_hi‖nonce) | | compute_server_seed_hash | BigUint64Array(8) | BigUint64Array(4) | Full hash of server seed | | seed_hash_truncated | BigUint64Array(8) | BigUint64Array(2) | First 2 elements (circuit leaf format) | | goldilocks_modulus | — | bigint | Returns p = 2^64 - 2^32 + 1 | | goldilocks_reduce | bigint | bigint | Reduce mod p |

Bundler notes

Vite — add to optimizeDeps.exclude:

optimizeDeps: { exclude: ['@rolly-dev/wasm-signer'] }

Webpack 5 — enable WASM experiments:

module.exports = { experiments: { asyncWebAssembly: true } };

Next.js — conditional exports auto-resolve: Node.js entry on server, browser entry on client.

License

MIT