Cipay allows you to pay fiat invoices with your ETH on Optimism.


Cipay lets you pay brazilian PIX* invoices with ETH on optimism. Just open the app, scan the invoice qrcode and sign a message. Example flow. Alice sold her UBI tokens for ETH and wants to pay Pix invoice with it. - She opens metamask on her phone, scans the invoice. - The app detects invoice amount in BRL and requests an equivalent amount in ETH + a fee. - She signs a meta transaction sending the amuont to cipay's wallet and sends everything to the backend; - The backend saves the request locally and broadcasts the meta tx sending ETH from Alice's to cipay's wallet; - The backend detects that the tx was mined and pays the invoice for Alice with BRL in cipay's bank account. *PIX is a system free to use system to allow payments and transfers between banks.

cipay showcase

How it's made

A minimally custodial/payment system like this would be impossible without a fast and cheap way to send ETH. Luckily L2s are coming fast. To make this app I used: - Meta transactions to run business logic before broadcasting the transaction to the network. - Optimism for fast and cheap ETH (or any token) transfers. - Starkbank as the bank to finalize the payment.

Technologies used