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There is no WhatsApp 'backdoor'

whispersystems.org

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Re: There is no WhatsApp 'backdoor'

#121

Post by joeblau »

frandroid wrote: post #79
joeblau wrote: post #23

There seems to be a pretty clear war going on between engineers and journalists lately. - Chris Latter [1] vs Business Insider [2] - Elon Musk vs (Bunch of outlets) - Moxie vs The Guardian I feel like journalists want to write a compelling story and engineers are on the other side like "No, those aren't facts!" I don't follow a lot of media outlets but it seems like journalists either lack the skills or don't care ab…

It would be a war if all these people were allied together. Neither the engineers nor the outlets mentioned here are allied parties. They're disparate across the board.

Yeah war is probably the wrong word to use — my vocabulary isn't that great :).

Re: There is no WhatsApp 'backdoor'

#122

Post by na85 »

imranq wrote: post #83
na85 wrote: post #55

Earlier quoted context omitted.

Trusting WhatsApp == trusting Facebook I can't think of a company I trust less than Facebook.

What about...Walmart, Glencore, Phillip Morris, Blackwater, Palantir...

Does Walmart actively deceive me? Not that I'm aware, but I don't shop there.

Never heard of Glencore or Phillip Morris.

As for Blackwater and Palantir, my impression from the media is they do exactly what they say. It's not like Palantir lies about harvesting data to give to government. I trust that they actually do do that.

None of those companies have posted fake news and altered the news algo with the express intent of manipulating users' mental states for reasons that basically boil down to "for the lols" and "let's see if we can make money from this".

Re: There is no WhatsApp 'backdoor'

#123

Post by oconnor663 »

ploxiln wrote: post #74
tucif wrote: post #22

Earlier quoted context omitted.

He does address this: Once the sending client displays a "double check mark," it can no longer be asked to re-send that message. That means a user is able to verify visually that the end-to-end is working. "users might not notice" doesn't seem to me as a strong argument to state this as a backdoor. This would imply not noticing that you don't have a green padlock on chrome is a backdoor too, and it clearly is not.

The "green padlock" was not considered enough because users would not be able to differentiate it from a big lock symbol within the page. Thus we got HSTS. (There was a time when browsers would color the entire URL bar yellow to indicate https, but that went out of favor many years ago.) Moxie deserves respect for the web vulnerabilities he discovered and raised awareness about years ago, and for his general competen…

> catastrophic sacrifices to make security applications popular and viable for the "lay person"

This isn't wrong, but it's unfair to bring it up without the most obvious counter-argument.

PGP provides absolutely zero security to the average person, because average people don't use it. HTTPS provides lots of security to the average person, whether or not they know what the green lock means, because lots of people use it. Adoption is a feature.

Of course both of these things are true. Security sacrifices for the sake of adoption suck. But let's not paint a picture of Signal as "desperate for popularity", as though that was a selfish and not security-minded goal. Be fair.

Re: There is no WhatsApp 'backdoor'

#124

Post by lisper »

tptacek wrote: post #78
avn2109 wrote: post #40

Earlier quoted context omitted.

Regardless of the merit of this specific accusational-and-denial cycle, the fact remains that Whatsapp is closed source crypto and there is no way in principle for the user to verify any security claims. I happen to trust Moxie's principles, but not as much as I distrust the relationship-with-government imperatives implied by FB's vast business interests.

There's "no way in principle"? How is this whole story not evidence to the contrary? The person who found this didn't use WhatsApp source code. Why do you feel that there's no way to verify closed-source software?

You can demonstrate the presence of a vulnerability in closed source software but there's no way to demonstrate (or even provide evidence of) the absence of any vulnerabilities.

Re: There is no WhatsApp 'backdoor'

#125

Post by mos_basik »

lwyr wrote: post #111

Why is moxie doing PR for WhatsApp?

>Even though we are the creators of the encryption protocol supposedly "backdoored" by WhatsApp, we were not asked for comment.

It's only a small step from criticism of WhatsApp crypto to criticism of Signal crypto. Why wouldn't moxie be interested?

Re: There is no WhatsApp 'backdoor'

#126

Post by akvadrako »

jMyles wrote: post #103
FiloSottile wrote: post #94

Earlier quoted context omitted.

> It could also pass back Bob's answers, and so Alice could have what appears to be a normal conversation - except that Alice only sees single ticks, instead of double blue ticks. No, it can't do this, because Bob's answers contain the "delivery receipt". Hence, the attack doesn't work on conversations. EDIT to reply: messages are sequential and "delivery receipts" are messages, so it would be visible if the attacker…

> Bob's answers contain the "delivery receipt". I've not seen any specific claims about the mechanism for the delivery receipt - can you link me to this? It's not even clear to me that the delivery receipt is signed.

It's also not clear that the server must forward all the delivery receipts before it forwards the later replies.

Could it just eat them all?

EDIT: after a quick look at the spec¹, it seems that it supports out-of-order messages, meaning the server could selectively eat receipts.

[1] https://whispersystems.org/docs/specifications/doubleratchet...

Re: There is no WhatsApp 'backdoor'

#127

Post by mtgx »

ycmbntrthrwaway wrote: post #12

> That would leak information to the server about who has enabled safety number change notifications and who hasn't , effectively telling the server who it could MITM transparently and who it couldn't; something that WhatsApp considered very carefully. I am not convinced. Why should this option exist at all? Even worse, it is disabled by default. Just enable notifications for everyone and demand verification. If you…

I think both Signal and WhatsApp "trust on first use" like SSH does it.

The issue here is that:

1) the vast majority of users have those MITM notifications off by default (because WhatsApp decided it's best that way)

2) WhatsApp generates its own keys in some scenarios, like when people switch their SIM cards, so the "trust on first use" that worked on the original SIM is gone out of the window now, and the users won't even know it because the notification is off by default.

Actually now that I think about it, this is why WhatsApp must have let the notifications off by default, because they knew they would generate their own keys this way, which would generate a lot of those notifications all the time.

Re: There is no WhatsApp 'backdoor'

#128

Post by FabHK »

mos_basik wrote: post #97
ycmbntrthrwaway wrote: post #12

> That would leak information to the server about who has enabled safety number change notifications and who hasn't , effectively telling the server who it could MITM transparently and who it couldn't; something that WhatsApp considered very carefully. I am not convinced. Why should this option exist at all? Even worse, it is disabled by default. Just enable notifications for everyone and demand verification. If you…

Caveat: I have never used WhatsApp and do not know anything about its interface or options (default or otherwise). >>[The choice to make these notifications "blocking" (i.e. to require manual verification) would] leak information to the server, etc., etc. >Why should this option exist at all? The option does not exist, and should not exist. That's the author's point there. You agree with him and with WhatsApp on that…

Difference is that the WhatsApp client re-encrypts the message with the new key from the server and re-sends it without user intervention ("non-blocking"), so even if you cared, you can't prevent it.

With the alternative, people that don't care could tick "verified" with or without verifying, but you could also click "cancel" (with or without verifying).

Re: There is no WhatsApp 'backdoor'

#129

Post by dangero »

psranga wrote: post #57

I take this blog post as confirmation that: 1) ANY one message can be intercepted even if the sender exhibits ideal levels of alertness [Whatsapp server drops message to recipient; sends a rekey request with a fake key; message is intercepted since fake key was generated by server. Sender will see a warning if they turned on that setting (default is to show no warning), but it's too late]. 2) Only Whatsapp has this v…

Best summary I've seen. There are two significant facts here that surprised me: 1. The double checkmark has security implications. How would a typical user know that? 2. Even if you are completely vigilant, follow best practices, etc, Whatsapp messages can be intercepted. They claim this is a "wontfix" UX choice. I'm skeptical why the non-default feature cannot even provide the protection that almost everyone assumed it would.

Re: There is no WhatsApp 'backdoor'

#130

Post by akvadrako »

amelius wrote: post #68
UncleMeat wrote: post #24

Earlier quoted context omitted.

If your threat model includes using a malicious app to send messages then you lose anyway. Nothing can ever be done to send messages securely using whatsapp if the client is neither trusted nor verified. This is true for basically all software that you use.

> This is true for basically all software that you use. And hardware too.

And that's why we have 2FA on separate devices or even hardware tokens. They allow some security even if the computer isn't trusted, like protection against replay attacks at a minimum.
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