Fairground

The idea

Platforms sit between creators, audiences and advertisers, take a cut, and decide what everyone sees. Fairground removes the middle: posts live on independent Nostr relays, the feed is ranked on the reader's device by a recipe they control, and money moves directly between the people involved. The project's own costs are a static site.

What I built

• A web app that ships unchanged as the iOS and Android apps (Capacitor). A new reader gets a good feed in seconds with no sign-up: an account is created silently, one optional tap picks topics, and a small embedding model in the browser (Transformers.js, about 23 MB) learns from likes and reading time without sending anything anywhere.
• Direct sponsorships as four signed events: offer, acceptance (which embeds the exact offer it accepts), a post labelled #ad, and a payment receipt checked against the public chain by its memo. Advertisers' payment records are public, so creators can see who pays before they accept.
• Hybrid signatures on every contract: Nostr's Schnorr signature plus ML-DSA-65 (FIPS 204), with key rotations signed by the previous post-quantum key. Creators are paid in USDC on Algorand, whose accounts can sign with Falcon-1024.
• Prices indexed to US CPI-U, so a late or long deal still pays what it was worth; index values arrive as signed attestations that each client trusts k-of-n, published monthly from the BLS by a GitHub Action.
• Anonymous audience surveys: one answer per throwaway key, carrying an RSA blind-signed token (RFC 9474), so nobody can link answers to people while advertisers can still recount them and catch invented answers.
• Fan support with an optional ad-free pledge, opt-in donations split between development and the relays a creator actually uses, and relays that can pledge to pass a share back to creators, all checkable from the chain.
• Username-and-password sign-in with no server: Argon2id derives a key that finds and opens an encrypted vault on relays, with a passkey (WebAuthn PRF) as a true second factor.

Hard problems, honestly

• No stablecoin is quantum-secure end to end today: the contracts and the creator's account are, but Algorand's consensus and USDC's issuer keys are still classical.
• Nobody can verify view counts without a central tracker, so deals are a flat fee per post, and survey counts are bounded by public participation rather than trusted.
• Donations to relays follow events a reader actually saw, credited to the relay that delivered them first and grouped by operator, so running extra relays to collect donations doesn't pay.
• Authenticator-app codes can't protect a vault anyone can copy, because nothing would enforce the check; a passkey's hardware secret can, so that is the second factor offered.

Run a relay

Relays store and deliver posts, and Fairground sends them a share of the donations from the people they serve. Phones and browser tabs can't be relays, so yours needs to run somewhere always on: a small cloud server, a home server or a hosted relay service. Install any Nostr relay software (strfry and nostr-rs-relay are common choices), set the operator pubkey in its NIP-11 information to the public key shown in the app, then open Create → Become a relay and enter its wss:// address. The app checks that the relay names you, publishes where donations should go, and shows what comes in and what you've passed on.

Engineering choices

• A protocol core in TypeScript that Node runs without a build step, covered by 79 unit tests, including attack cases (forged edits, swapped signatures, changed terms, underpayment, invented survey answers). Each security rule was mutation-checked: removing it fails a test.
• An end-to-end test drives the built app in Chrome against a local relay with labelled test fixtures: onboarding, ranking, posting, sponsorship, account sync to a second device, and the on-device model. The demo video is recorded from real published posts only.
• The app runs under this site's strict Content-Security-Policy. The AI runtime is served from the app itself, and the library's blob: loader is switched off so scripts never need more than 'self'.