MeshPay: A Decentralized Multi-Hop Offline Payment Protocol via Hybrid AES-RSA Cryptography and BLE Mesh Routing

Digital payment infrastructures face critical single points of failure in environments lacking cellular or Wi-Fi coverage. This paper presents MeshPay, a decentralized offline payment protocol that combines Bluetooth Low Energy (BLE) ad-hoc mesh networking with hybrid cryptography. MeshPay enables offline smartphones to route encrypted transaction payloads across intermediate zero-knowledge relay nodes until the payload reaches an internet-connected gateway node, which forwards it to a backend server for settlement. Security is provided by hybrid AES-256-GCM symmetric payload encryption and RSA-2048 asymmetric key encapsulation, so transit relay nodes cannot inspect or modify transaction parameters. Replay attacks are mitigated using cryptographically random nonces. We evaluate the architecture using Kotlin Android clients, a Spring Boot REST API, and a PostgreSQL database, and demonstrate reliable multi-hop payment routing within BLE MTU limits using a custom byte-chunking engine.