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Hey there! You are using WhatsApp: Enumerating Three Billion Accounts for Security and Privacy
Gabriel K. Gegenhuber, Philipp Ã. Frenzel, Maximilian Günther +2
WhatsApp, with 3.5 billion active accounts as of early 2025, is the world's largest instant messaging platform. Given its massive user base, WhatsApp plays a critical role in globa…
Careless Whisper: Exploiting Silent Delivery Receipts to Monitor Users on Mobile Instant Messengers
Gabriel K. Gegenhuber, Maximilian Günther, Markus Maier +4
With over 3 billion users globally, mobile instant messaging apps have become indispensable for both personal and professional communication. Besides plain messaging, many services…
SIMulator: SIM Tracing on a (Pico-)Budget
Gabriel K. Gegenhuber, Philipp Ã. Frenzel, Adrian Dabrowski
SIM tracing -- the ability to inspect, modify, and relay communication between a SIM card and modem -- has become a significant technique in cellular network research. It enables e…
Prekey Pogo: Investigating Security and Privacy Issues in WhatsApp's Handshake Mechanism
Gabriel K. Gegenhuber, Philipp Ã. Frenzel, Maximilian Günther +1
WhatsApp, the world's largest messaging application, uses a version of the Signal protocol to provide end-to-end encryption (E2EE) with strong security guarantees, including Perfec…
Diffie-Hellman Picture Show: Key Exchange Stories from Commercial VoWiFi Deployments
Gabriel Karl Gegenhuber, Florian Holzbauer, Philipp Frenzel +2
Voice over Wi-Fi (VoWiFi) uses a series of IPsec tunnels to deliver IP-based telephony from the subscriber's phone (User Equipment, UE) into the Mobile Network Operator's (MNO) cor…