Strachey Lecture - Professor Alastair Beresford

Strachey Lecture: Professor Alastair Beresford, University of Cambridge Title: Hiding in Plain Sight: The promises and pitfalls of secret communication Abstract: The history of secret communication has been driven by the need for both confidentiality and anonymity. Over the last thirty years we’ve seen significant progress in the digital space, with encryption now widely deployed on the web and in personal messaging apps. Protecting the identity of communicating parties is comparatively underexplored, despite the fact that the timing, frequency, and volume of network traffic can often reveal who is talking to whom, even if the communication itself is encrypted. These technological developments also sit at the centre of a wider societal debate: secure communications are simultaneously essential to protect individual autonomy and foster commercial innovation, yet they can also pose serious operational challenges to law enforcement and the oversight of public safety. This lecture explores the topic through the design and deployment of CoverDrop, a secure communication system designed in collaboration with The Guardian. We will walk through the seven-year journey from our initial research idea to a real-world deployment that now serves as the default channel by which news sources and whistleblowers contact The Guardian. We’ll explore the technical hurdles that arise when providing confidential and plausibly deniable communication inside a news app at scale, and reflect on whether these technologies, and indeed other emerging ideas in the digital landscape, are an overall benefit to society. Bio: Alastair Beresford is Professor of Computer Security and Head of the Department of Computer Science and Technology at the University of Cambridge. His research examines the security and privacy of large-scale distributed systems, with a particular focus on networked mobile devices. His work has uncovered security vulnerabilities in platforms produced by Apple and Google, and he collaborates with The Guardian on secure communication technologies used by whistleblowers and news sources. He has received several major accolades, including the 2019 Google Security and Privacy Prize and the 2026 IEEE Pervasive Computing Test of Time Award. The Strachey Lectures are generously supported by OxFORD Asset Management