FoSAM: Forward Secret Messaging in Ad-Hoc Networks

Computer Science > Cryptography and Security [Submitted on 13 Mar 2026] FoSAM: Forward Secret Messaging in Ad-Hoc Networks Daniel Schadt, Christoph Coijanovic, Thorsten Strufe 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. Comments: Invited paper to the Journal of Science & Technology on Information and Communications Subjects: Cryptography and Security (cs.CR) Cite as: arXiv:2603.12871 [cs.CR]   (or arXiv:2603.12871v1 [cs.CR] for this version)   https://doi.org/10.48550/arXiv.2603.12871 Focus to learn more Submission history From: Daniel Schadt [view email] [v1] Fri, 13 Mar 2026 10:17:18 UTC (1,319 KB) Access Paper: HTML (experimental) view license Current browse context: cs.CR < prev   |   next > new | recent | 2026-03 Change to browse by: cs References & Citations NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)