AWS Architecture

PayOff

A distributed, peer-to-peer, offline, failure resistant payment system. Hack@Brown2026 project made by Aarul Dhawan, Krish Gandhi, Ethan Park, and Abhishek Ramakrishnan.

This project was created to solve a common problem in metropolitan areas: needing to send money between peers when networks are shotty or unreliable. To build this project, we utilized topics from distributed systems, networking and security theory. We decided to use AWS and Swift to make the project feel more like a real, professional tool. After nearly a day straight of work, we ended up with a product that we are proud of.

PayOff works off of Apple's Bonjour services, to create a peer to peer network of devices that does not require WiFi or cellular data to communicate. The devices use a protocol similar to SWIM Failure Detection to keep track of devices in the mesh. When two peers need to make a transaction, the buyer and seller go through a cryptographically secure handshaking progress. After this, only the PayOff server will be able to decrypt the message. This means the transaction data can be safely shared throughout the network. When any device in the network regains Internet access, the device communicates with the PayOff servers to execute all pending transactions. This device then reports back to other devices in it's view of the mesh network. Therefore, the PayOff system gets stronger and stronger with each device that joins the local network.