I remember receiving the downvote brigade[1], when Moxie himself said that I should trust WhatsApp without having the source code and the ability to put it on my device. We (even a "smart" community like HN) clearly do not have the ability to think critically about security, and even when our leaders are sincere -- and I really don't mean to suggest Moxie/Signal was complicit in this move -- we still rush to defend o…
> when Moxie himself said that I should trust WhatsApp without having the source code and the ability to put it on my device. What are you talking about? All I can see there is that you asked for the source code of the QR generator and he delivered. He does not say you should trust WhatsApp.
Rather he pointed out that what you see in the WhatsApp UI is meaningless because you have no way of knowing that the app you're running matches the code Moxie linked, or that the code your friends are running does. Moxie replied with a link to the QR generation code but this didn't answer geocar's question, probably because there is no answer.
Here's a simple way to put it. End-to-end messaging security is assumed to be (at least traditionally) about moving the root of trust. Before you had to trust Facebook. Now you don't. A closed source app that can update on demand doesn't move the root of trust and this probably doesn't match people's intuitive expectations of what it does.
Many people have pointed out similar things to what geocar has pointed out: E2E encryption is essentially meaningless if you can't verify what your computers are actually doing. Unfortunately fixing this is a hard problem.
I wrote about this issue extensively in 2015 in the context of encrypted email and bitcoin apps (where you can steal money by pushing a bad auto update):
https://moderncrypto.org/mail-archive/messaging/2015/001510....
I proposed an app architecture that would allow for flexible control over the roots of trust of programs using sandboxing techniques. Unfortunately there's been very little (no?) research into how to solve this problem, even though it's the next step in completing the journey that Signal has started.
By the way, just to make it super clear, the work Moxie has done on both Signal and WhatsApp is still excellent. It is, as I said, necessary work. But the Guardian has unfortunately not understood security well enough, nor have people from the cryptography community really helped journalists understand the limits of this approach. Nor has Facebook, I think.