Episode 16: Contact Discovery in Mobile Messengers!

Contact discovery is a core feature in popular mobile messaging apps such as WhatsApp, Signal and Telegram that lets users grant access to their address book in order to discover which of their contacts are on that messaging service. While contact discovery is critical for WhatsApp, Signal and Telegram to function properly, privacy concerns arise with the current methods and implementations of this feature, potentially resulting in the exposure of a range of sensitive information about users and their social circle. Do we really need to rely on sharing every phone number on our phone in order for mobile messengers to be usable? What are the privacy risks, and do better cryptographic alternatives exist for managing that data? Joining us are researchers looking exactly into this problem, who will tell us more about their interesting results. Links and papers discussed in the show: All the Numbers are US: Large-scale Abuse of Contact Discovery in Mobile Messengers (https://www.ndss-symposium.org/wp-content/uploads/ndss2021_1C-3_23159_paper.pdf) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Alexandra Dmitrienko, Christian Weinert, and Christoph Hagen.