FoSAM: Forward Secret Messaging in Ad-Hoc Networks

2026-03-13

AI Summary

This work addresses the lack of forward secrecy in existing decentralized communication systems operating over unreliable ad hoc networks, where device compromise can lead to exposure of historical messages. To overcome this vulnerability, the paper introduces FoSAM, a novel protocol that, for the first time, enables non-interactive, anonymous, and forward-secure message transmission using only the recipient’s public key—without requiring pre-shared keys or online interaction. Specifically designed for resource-constrained, intermittently connected wireless ad hoc networks, FoSAM provides provable anonymity and forward secrecy. Large-scale mobility simulations demonstrate a high message delivery rate of 92%–99%, and a functional prototype has been successfully implemented and tested on the Android platform.

Technology Category

• Multiagent Systems: Agent Communication
• Search and Optimization: Distributed Search
• Application Domains: Security

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Decentralized Web and Fediverse systems
• Security and Privacy: Large-scale security measurements
• Responsible Web: Measurement, analysis, and circumvention of Web censorship

Abstract

Apps such as Firechat and Bridgefy have been used during recent protests in Hong Kong and Iran, as they allow communication over ad-hoc wireless networks even when internet access is restricted. However, these apps do not provide sufficient protection as they do not achieve forward secrecy in unreliable networks. Without forward secrecy, caught protesters' devices will disclose all previous messages to the authorities, putting them and others at great risk. In this paper, we introduce FoSAM, the first protocol to provide proven anonymous and forward secret messaging in unreliable ad-hoc networks. Communication in FoSAM requires only the receiver's public key, rather than an interactive handshake. We evaluate the performance of FoSAM using a large-scale simulation with different user movement patterns, showing that it achieves between 92% and 99% successful message delivery. We additionally implement a FoSAM prototype for Android.

Problem

• forward secrecy
• ad-hoc networks
• secure messaging
• unreliable networks
• privacy

Innovation

• forward secrecy
• anonymous messaging
• ad-hoc networks
• non-interactive communication
• secure protest communication