Aleph Hackathon

Every digital loyalty programme buys convenience by handing a company your purchase history. Sello removes that party.

A merchant signs a receipt at the counter and hands over a QR. The customer's phone reads the receipt with a model running locally, works out how much of their spending goes to independent businesses, and discards the receipt. Only the score is published on-chain, with a reference to the merchant's signature.

A shop reading that score learns you are a proven local regular. It does not learn where you shopped, what you bought or how much you spent. Independent salons, barbers and cafés get a way to reward regulars without building an app or buying a customer database and the customer's standing travels with them when they switch shops.

Built from scratch during the hackathon. Local inference via QVAC, score anchored on an EVM contract.

Why it needs QVAC

Sending receipts to a hosted model would recreate the exact problem the product claims to solve. The receipt exists on the device for one function call and is never transmitted or stored.

Trust boundary, stated up front

The merchant signature stops a customer inventing purchases. The classification itself is not yet attested, and the merchant is trusted not to sign fictional sales. Production moves the classification into a TEE so the device emits a signed attestation of the model's verdict. Named here rather than left for a judge to find.

What's built

Three screens: counter issues a signed receipt, phone verifies and scores it locally, score page publishes and reads back. One contract, LocalSpendScore, storing a score, a visit count and a signature reference. No NFT, no metadata.

Not built: redemption, multi-merchant onboarding, customer wallet abstraction, attested classification. Scoped to one working loop.