OverTheEther

Crypto payments often rely on scanning QR which can be a cumbersome user experience. That is why we decided to build tap-to-pay experience offered by Google/Apple Pay for crypto payments.

Initially, we explored whether we could utilize the newly introduced NFC APIs in iOS 18.1. However, after swiftly prototyping the idea in native Swift, we realized that these APIs are still heavily restricted behind commercial agreements.

As a result, we opted to use ultrasound as a backup solution. This approach offers a quick, frictionless, and seamless way to enable zero-setup, permissionless, and communication between the merchant’s POS and the user’s crypto wallet. This might also be considered useful as an alternative in low light conditions, or other situations in which QR codes cannot work.

Smart Contracts

The Smart Contract architecture consists of Smart Wallets, that allow merchants to claim money off of buyers. Using EIP712, buyers create signatures that get shared with the merchant upon a payment request. These signatures enable merchants to claim funds at any time, possibly also at a later stage, payments do not have to be instant. This way we enable an offline buyer experience, similar to Apply Pay.

The Smart accounts are also deployed automatically via a factory. via the use of create2 the smart wallet address is made deterministic, preventing confusion for users. and since the factory is deployed everywhere on the same address, the user just has a single address to receive funds on.

The frontend consists of a NextJS mobile-first web app. Initially we planned to use Swift and an iOS app, but because of Apple's constraints regarding NFC usage for developers, we pivoted to a web-app that uses ultrasound for transaction transmission. The webapp incorporates tailwind, ggwave, viem, CDP SDK, Dynamic Wallet SDK, and other libraries to make all features possible.