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.
Eh, I kind of agree with geocar's point in the original thread. Moxie shared source code to "a" QR generator. Is there any way to verify that this code is what's running inside of WhatsApp?
A less obvious one is to make it possible to detect WhatsApp cheating. This isn't perfect, but someone only needs to detect it cheating once and then your name is mud.
One such way I proposed: If I can create my own key, then I can pass my public key out of band to someone who can mitm[1] themselves and verify that the message on the wire was encrypted and only encrypted with my key, and I can mitm myself to verify that my device only ever sends things encrypted with my own key. Tooling for the protocol is non-existent, and despite someone claiming they could do it in 10 seconds, they never followed up with instructions on how I could do it in 10 seconds.
This also allows other non-WhatsApp versions of the client, which may make things much more difficult for FaceBook (since now they can't upgrade legitimate clients if they discover a protocol-level problem) but the Internet has some experience with protocols.
- source code can be looked at, even verified, but it's hard. (Remember many bugs in OpenSSL, for example.)
- but binaries, too, can be disassembled, even verified. It might be harder, but it's a shades of grey, not binary (ha).
- even if you have the source code, you have to ensure that the binaries actually distributed to your phone correspond to the source code. That muddles the issue further.
I have no doubt Moxie acted in good faith and wanted to expand encryption to a large number of users, but this is just another example of why proprietary software cannot be trusted.
Any and all proprietary implementations of the Signal protocol are now suspect. OWS should denounce these implementations as least as firmly as they do interoperable open source Signal client forks.
You are not being sincere. You are implying that GP is a paid troll of spooks.
They don't. Moxie does not want the forks to use his servers or the name of his app, that is all.
I just want to voice my opinion that maybe 1 in 100 people have Moxie's integrity and ethics.
Your "further" stance is not supported by the evidence. You might disagree with the design choices, but they're not negligence or "complicity". Moxie answered, in the other thread, that
a fact of life is that the majority of users will probably not verify keys. That is our reality. Given that reality, the most important thing is to design your product so that the server has no knowledge of who has verified keys or who has enabled a setting to see key change notifications. That way the server has no knowledge of who it can MITM without getting caught. I've been impressed with the level of care that WhatsApp has given to that requirement. I think we should all remain open to ideas about how we can improve this UX within the limits a mass market product has to operate within, but that's very different from labeling this a "backdoor."
https://tobi.rocks/2016/04/whats-app-retransmission-vulnerab...
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 our champions so quickly that we don't even think about what's going on.
However something really important is that this might be mere incompetence: FaceBook might not have any mechanism for launching this attack, they just thought the notification message was annoying so they didn't display it. To that end we need to be vigilant about stupidity as well.
Where does it end? Will we actually stop being okay with buffer overflows and sloppy programming? Or are we going to continue trying to "be safer" and use "safe languages" and continuing to try to solve the problem of too much code to read clearly with more code.
[1]: https://news.ycombinator.com/item?id=11669395