Transactions in the Wild: A Secure, Offline Architecture for Ad-Hoc Mobile Payments

This paper presents a secure and lightweight mobile payment system that works entirely offline, without relying on the internet, cloud servers, or any centralized authority. The system allows two users to exchange digital payments directly using their mobile devices and short-range communication such as Bluetooth. To ensure security without storing sensitive data, each device creates a unique identity from its physical hardware properties. Digital signatures are used to protect the transaction, and nearby trusted devices act as witnesses to verify its validity and approve the release of funds. This witness-based process ensures the system is resistant to fraud and double-spending, even in isolated environments. The design is energy-efficient and uses only a small portion of a phone’s processing and battery resources. Simulations show that the system performs reliably and quickly in dynamic environments, making it suitable for use in remote areas, emergency situations, or anywhere network infrastructure is unavailable.