Daniel Hugenroth

The picture shows a smartphone and the imprint of a newspaper. The smartphone displays a screen from the SecureMessaging feature showing a key digest. The newspaper imprint shows the same digest. The digest consists of a number of randomly-looking letters and digits.

One of my favourite CoverDrop details: out-of-band verification of the trusted organization key which signs the entire key hierarchy. Its digest is included in the imprint of every printed Guardian newspaper, removing the need to trust CAs 🔑🗞️ more details: www.coverdrop.org

Audits of AI/ML systems while protecting model IP and keeping the audit data confidential 🤫

@inxoy.bsky.social is at the ICML TAIG workshop today, presenting our work on Attestable Audits: arxiv.org/html/2506.23... with Bill Marino and @arberesford.bsky.social

Super excited that Jenny is presenting our new paper on "Web Authentication and Recovery in the Age of E2EE" at PETS today! 🎉🎉

Tons of interesting insights for a world in which we are moving away from passwords, and E2EE data becomes more long-term and critical. petsymposium.org/popets/2025/...

↩️ Back-link to the launch post: bsky.app/profile/lamb...

There are a lot of insights in both the original PETS paper (petsymposium.org/2022/files/p...) and Diana's PhD thesis (www.repository.cam.ac.uk/items/ec87dd...).

CoverDrop involved users from the very beginning—avoiding the “solution looking for problem” trap. Big shout out to @mansoor.bsky.social , Diana, and @arberesford.bsky.social for getting this right from the very beginning by running two very insightful workshops with journalists and engineers.

And if you like to learn more about the CoverDrop research behind SecureMessaging: www.coverdrop.org

This announcement really should have our lead Rustaceans @itsibitzi.dev and @zekehg.bsky.social on top 🦀! CoverDrop's implementation journey has been demonstrating the immense strengths that lie in Rust's type system and the mature tool chain. Looking forward to all the talk in September!

The Guardian’s new whistleblower tool buries leaks to journalists within its own readers’ everyday traffic Think "I am Spartacus!" — but for leakers.

The Guardian app’s own data flows make leaks indistinguishable from regular traffic — cutting off one of the easiest ways for a repressive government or a corporate boss to identify a leaker. www.niemanlab.org/2025/06/the-...

GitHub - guardian/coverdrop: Blowing the whistle through a news app Blowing the whistle through a news app. Contribute to guardian/coverdrop development by creating an account on GitHub.

Yes, the full CoverDrop system is open-source, we had an OTF-sponsored audit, and we have shared the design early with other researchers for feedback. github.com/guardian/cov...

The Guardian launches Secure Messaging, a world-first from a media organisation, in collaboration with the University of Cambridge Secure Messaging is a new innovation for confidential story-sharing and source protection, underpinning the Guardian’s commitment to investigative journalism. The Guardian has published the open sourc...

Congratulations @lambda.bsky.social! Today @theguardian.com is launching a new way for whistleblowers to anonymously contact journalists, based on years-long research by Daniel and other colleagues. www.theguardian.com/gnm-press-of...

Thank you so much @martin.kleppmann.com for all your help, guidance, and feedback during this project! Especially with the tricky bits around key rotation and concurrency. And glad that we were able to distill some insights from the production world already into our P79 course.

There’s a lot more to say, and I’ll highlight some aspects that I’m particularly excited about over the next few weeks.

Our CoverDrop white paper has a lot more technical details and we are immensely grateful to everyone who have provided us with valuable feedback throughout this project: www.cl.cam.ac.uk/techreports/...

Whistleblowing tech based on Cambridge research launched by the Guardian Whistleblowers can contact journalists more securely thanks to a new confidential and anonymous messaging technology co-developed by University of Cambridge

The university team has prepared a lil’ announcement as well: www.cam.ac.uk/research/new...

In a dangerous era for journalism – a powerful new tool to help protect sources Today, the Guardian, in collaboration with the University of Cambridge, launches Secure Messaging, a world-first from a media organisation

The launch article by Katharine Viner provides a great overview on how CoverDrop works, our collaboration with The Guardian, and why this system is so important: www.theguardian.com/membership/2...

We launched CoverDrop 🎉 providing sources with a secure and anonymous way to talk to journalists. Having started five years ago as a PhD research project, this now ships within the Guardian app to millions of users—all of which provide cover traffic. Paper, code, and more info: www.coverdrop.org

GitHub repo here: github.com/lambdapionee...

PETS paper here: petsymposium.org/popets/2024/...

Panorama of Linz

Greatly enjoyed talking at JKU Linz about our Sloth 🦥 library which uses Secure Enclaves (SEs) for key stretching and deniable encryption. Importantly, it works around Android/iOS API limitations and, therefore, Sloth is available to regular apps on most smartphones without modifications.

The final slides are online now: bsky.app/profile/lamb...

It's done! The final lecture slides and notes for "P79 Cryptography and Protocol Engineering" are now online: www.cl.cam.ac.uk/teaching/242... 🎉. This is the first time that @martin.kleppmann.com and I have done this course—we very much welcome feedback, corrections, and suggestions for next time

The slides are updated as-we-go on the course website: www.cl.cam.ac.uk/teaching/242... Currently, the highlight are the great X25519/Ed25519 slides by Martin. Content should be complete by begin of March :)

The lectures are not recorded, but we will upload the slides and lecture notes online. There will be another post when the full set becomes available.

We believe that simply preaching "Don't roll your own crypto" does not cut it anymore—the next generation of engineers and researchers needs to be able to critically evaluate available implementations and competently navigate risks and trade-offs.

I am quite excited that our brand-new module "P79: Cryptography and Protocol Engineering" has its first lecture today! @martin.kleppmann.com and I designed the course to bridge the gap between mathematical ideas and the challenge of implementing secure cryptography in the real world. @cst.cam.ac.uk

The PaPoC workshop is once again accepting submissions on distributed consistency. Deadline 15 January papoc-workshop.github.io/2025/cfp.html

And a proper domain handle 🥳

My CS department @cst.cam.ac.uk is now on Bluesky, with a properly validated domain handle. Please give them a warm welcome!

Android HKDF implementations This article discusses several open-source implementations of the HKDF scheme for Android. Since HKDF is a relatively simple algorithm, it allows for a good case study of cryptographic code. The prima...

I went down a rabbit hole studying HKDF implementations for Android and wrote up some impressions: www.danielhugenroth.com/posts/2024_0...