Viewing profile — martinralbrecht

Note that WhatsApp as a web client, too: https://eprint.iacr.org/2025/794

We did reverse engineer it and we're cryptographers not reverse engineering experts https://eprint.iacr.org/2025/794

WhatsApp's end-to-end encryption has been independently investigated: https://kclpure.kcl.ac.uk/ws/files/324396471/whatsapp.pdf Full version here: https://eprint.iacr.org/2025/794.…

Telegram's symmetric cryptography has been reviewed by cryptographers: https://mtpsym.github.io/

We explain this under the heading "A Somewhat Opinionated Discussion" here: https://mtpsym.github.io/ which is our security analysis of MTProto's symmetric cryptography.

NIST responded: https://groups.google.com/a/list.nist.gov/g/pqc-forum/c/W2VO ...

NIST responded: https://groups.google.com/a/list.nist.gov/g/pqc-forum/c/W2VO...

"As independent information security and cryptography researchers, we build technologies that keep people safe online. It is in this capacity that we see the need to stress that th…

- Issue 1: using uninitialised keys. - Issue 2: IV reuse in AES-GCM when a file is re-encrypted after an update. - Issue 3: a malicious server can place a chosen key in a victim us…

Cool, thanks! That's interesting to know. Do you know how they deal with FOI and auditable communications in this case? PS: I talked about the seemingly unexploitable IND-CCA vulne…

Since Matrix (and thus BundesMessenger?) currently doesn't provide standard security guarantees for its end-to-end encryption (the mitigation to the "Simple confidentiality break" …

re: implementation bugs: Almost, but not quite. See https://nebuchadnezzar-megolm.github.io/#anticipated-questio... Also note that in the review of the ecosystem the Matrix develop…

We explain how this works in Appendix A of https://nebuchadnezzar-megolm.github.io/static/paper.pdf but it's also a nice little exercise to work out how this breaks confidentiality…

A quick comment on this, we did address this in our paper: "In environments where cross-signing and verification are enabled, adding a new unverified user adds a warning to the roo…

This isn't correct. Several of our attacks succeeded without any warnings popping up. Furthermore, you need to distinguish between what Element happened to do (which users may or m…

We had working exploits for those vulnerabilities where exploiting them wasn't immediately obvious. We shared those with the Matrix developers but didn't publish them because there…

Indeed: > While the Matrix specification does not require a mitigation of this behaviour, when a user is added to a room, Element will display this as an event in the timeline. Thu…

Unfortunately, it is not quite so simple: > Does this mean that Matrix does not provide confidentiality and/or authentication? > Matrix and its implementations can, after today’s f…

Several of these bugs were indeed on the protocol level: https://nebuchadnezzar-megolm.github.io/

This is discussed by the research team who reported these issues (I'm one of those researchers) at: https://nebuchadnezzar-megolm.github.io/ > Are these attacks design flaws in the…

Writeup of these vulnerabilities and attacks by the research team who reported them: https://nebuchadnezzar-megolm.github.io/

- Matrix announcement: https://matrix.org/blog/2022/09/28/upgrade-now-to-address-en... - Write-up by research team: https://nebuchadnezzar-megolm.github.io/

Write-up of the vulnerabilities and attacks by research team who reported them: https://nebuchadnezzar-megolm.github.io/