ABSTRACT – Silent Tracking of Encrypted Messaging Users via Protocol Side-Channels Researchers from the University of Vienna and SBA Research identified a protocol-level side-channel in WhatsApp and Signal that enables adversaries to monitor user device activity using only a phone number. This vulnerability exploits automatic delivery receipts for crafted messages, such as reactions to nonexistent … Leggi tutto Silent Delivery Receipts as Persistent Surveillance Vectors in WhatsApp – Signal: Device Activity Inference, Resource Exhaustion and Privacy Implications as of December 2025