Advanced Browsing Protection for Facebook Messenger

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Presented at Real World Crypto 2026 by

Emma Connor

Artem Ignatyev

Kevin Lewi

Facebook Messenger recently added a new feature called Advanced Browsing Protection, which is based around a private information retrieval (PIR) protocol that is triggered when a user clicks on a link in a Messenger end-to-end encrypted chat thread. The user's link is matched against a large server-side database of malicious links, without revealing the plaintext link or the outcome of the match to the server. We will discuss the design decisions we made and also the challenges we faced when realizing this cryptographic primitive in practice.