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There is no WhatsApp 'backdoor'

whispersystems.org

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Re: There is no WhatsApp 'backdoor'

#181

Post by JCzynski »

runn1ng wrote: post #59
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.

A little. Without reading the Guardian piece, I wouldn't even guess that delivery notifications have anything in common with security properties. In other words, the messages are secure only when there is a double checkmark, not just a single checkmark. How am I supposed to know that?!? I am not even sure what do the checkmarks mean. Frankly, that's not a "backdoor", that's just a poorly thought out GUI (in my opinio…

The single/double checkmark is used with Signal's client as well. When you're sending unsecured texts, you get a single checkmark when you send it; when you are sending encrypted messages, a lock symbol and a single check when sent, and a double check when received.

Re: There is no WhatsApp 'backdoor'

#182

Post by valarauca1 »

tyrust wrote: post #9

>The WhatsApp clients have been carefully designed so that they will not re-encrypt messages that have already been delivered. Once the sending client displays a "double check mark," it can no longer be asked to re-send that message. This prevents anyone who compromises the server from being able to selectively target previously delivered messages for re-encryption. Can this be verified? Can this be verified to be th…

>Can this be verified? Can this be verified to be the case 100% of the time? Is there anything stopping the client from lying to a user

No.

OpenWhisper system otherwise GPLv3 auditable libraries are closed source for usage by WhatsApp and Facebook Messenger. Either OpenWhisper systems has elected not to enforce their copyright (in which case you could make a BSD/MIT/Apache fork of their software), OR they have consented to Facebook allowing them to circumvent the license.

Eitherway. The code in WhatsApp is off limits for anyone not working with Facebook so well never know. Closed source crypto is bad. We only have WhatsApp's word the Facebook libraries have no modifications.

Re: There is no WhatsApp 'backdoor'

#183

Post by kordless »

joeblau wrote: post #70
hackuser wrote: post #47

Earlier quoted context omitted.

I don't know what happened here, but ... Let's avoid our own bias of automatically believing the engineers are in the right; they are fallible people, no more or less honest or prone to error than journalists. Every news story that breaks, involving any person or industry, gets the same response: It's false, they didn't ask us, etc. etc. Therefore, that response is not an indication that something is wrong (or right)…

You're right. Everyone is fallible and I'm all for mistakes being made — We are all human. I also agree that the immediate snap response tells us nothing. Based on the BI story, I know a few people that have actually already uninstalled WhatApp for fear of a backdoor. What I wish is that there was a better way for these two entities to communicate rather than finger pointing and name calling so that we as consumers o…

Name calling results in reassigning fear. People are afraid of the unknown and so try to box it up in something digestible they can fear less. We tend to blame others because it's easy and cheap to do so. If you are wrong, that means I'm right and so then I wasn't wrong about it and don't have to think about it anymore. And you are wrong, so why would I think about it again?

I think it's interesting the entities are not two, but many and one at the same time. Elon Musk is an individual and he is also part of the press process. My rationale is that the press includes everyone in the press, including the people writing the stories and the people in the stories.

We know Musk. He doesn't know us.

Re: There is no WhatsApp 'backdoor'

#184

Post by rebuilder »

sebleon wrote: post #18

At the end of the day, it comes down to trusting WhatsApp. Even without a backdoor in their protocol, they can easily do all kinds of things. For instance, it could instruct specific clients to encrypt and send each message twice: one for the recipient, and one for the WhatsApp server. As long as this was off for 99.9% of users, it's unlikely that security researchers would ever detect this.

And anyone with sufficient access could push an update from the app store to a selected target that bypasses the normal security protocols of any given messaging app. Who checks their app store downloads against source code?

Re: There is no WhatsApp 'backdoor'

#185

Post by Normal_gaussian »

rndgermandude wrote: post #170
jMyles wrote: post #5

Color me still-unconvinced. This retort does not address the fundamental point made in the Guardian piece: > “[Some] might say that this vulnerability could only be abused to snoop on ‘single’ targeted messages, not entire conversations. This is not true if you consider that the WhatsApp server can just forward messages without sending the ‘message was received by recipient’ notification (or the double tick), which u…

This allows WhatsApp to MITM. Whatapps can rekey both Alice and Bob, decrypt both their messages from that point onwards (incl unsent messages) and forward them re-encrypted with their real keys. The only notification might be that rekeying warning, if the users have turned it on. In this scenario even the double-checkmarks are present. This is contrary to WhatsApp's claim that even they cannot snoop. PS: I just chec…

I can confirm that the rekeying notifications are off by default, also Android

Re: There is no WhatsApp 'backdoor'

#186

Post by lisper »

tptacek wrote: post #155
lisper wrote: post #154

Earlier quoted context omitted.

> the programming language used to represent a computer program has nothing fundamentally to do with whether it can be verified That's not true. The design of a language can make it easier to verify with respect to certain properties. For example, it is much easier to verify that a typical Python program does not dereference dangling pointers than a typical C program. It is true that open source does not help as much…

You're using a word, "easier", that is keeping us off the same page. I agree that Haskell programs are easier in many senses to verify than PHP programs. But our field does formal methods verification of assembly programs, for instance by lifting them to an IR.

That's news to me. At least it's news that this is actually practical for any interesting cases (i.e. real crypto code). Do you have a reference?

Re: There is no WhatsApp 'backdoor'

#187

Post by rebuilder »

So full-on paranoia mode on: What would you do if you wanted to compare safety numbers? I'm guessing most people would call and read out the code.

How far are we from targeted interception of calls, with replacement of key phrases? Voice synthesis seems to be there more or less, if I understood Adobe's recent demo correctly, but real-time parsing of conversations to determine where to intervene is probably not close yet.

Re: There is no WhatsApp 'backdoor'

#188

Post by lisper »

tptacek wrote: post #164
lisper wrote: post #147

Earlier quoted context omitted.

Sure, but so what? Hard != impossible. EDIT: WTF people? Why is every response to this comment being downvoted into oblivion? The sibling comment to this one ( https://news.ycombinator.com/item?id=13395657 ) was killed in a matter of minutes despite being (IMHO) a perfectly reasonable and constructive response.

Votes aren't why that comment is dead --- note that it doesn't say "flagged". There is stuff that happens behind the scenes that [deads] users, especially new accounts; I think some of it might be voting ring related but not sure. (That comment is incorrect but I agree with you that it's constructive).

It seems to have come back from the dead too :-)

Re: There is no WhatsApp 'backdoor'

#189

Post by ehsankia »

rndgermandude wrote: post #170
jMyles wrote: post #5

Color me still-unconvinced. This retort does not address the fundamental point made in the Guardian piece: > “[Some] might say that this vulnerability could only be abused to snoop on ‘single’ targeted messages, not entire conversations. This is not true if you consider that the WhatsApp server can just forward messages without sending the ‘message was received by recipient’ notification (or the double tick), which u…

This allows WhatsApp to MITM. Whatapps can rekey both Alice and Bob, decrypt both their messages from that point onwards (incl unsent messages) and forward them re-encrypted with their real keys. The only notification might be that rekeying warning, if the users have turned it on. In this scenario even the double-checkmarks are present. This is contrary to WhatsApp's claim that even they cannot snoop. PS: I just chec…

I'm confused. The way I understand it is that once the double checkmark appears, those messages are locked in and never rekeyed. That means once you see those checkmarks, you're guaranteed no one can snoop on that message anymore.

Assuming you have the notification on (Which anyone who cares about security could and should turn on), once you see a warning, you could just delete all messages that don't have the double checkmark (if any) and not send new ones.

Re: There is no WhatsApp 'backdoor'

#190

Post by makomk »

JCzynski wrote: post #181
runn1ng wrote: post #59

Earlier quoted context omitted.

A little. Without reading the Guardian piece, I wouldn't even guess that delivery notifications have anything in common with security properties. In other words, the messages are secure only when there is a double checkmark, not just a single checkmark. How am I supposed to know that?!? I am not even sure what do the checkmarks mean. Frankly, that's not a "backdoor", that's just a poorly thought out GUI (in my opinio…

The single/double checkmark is used with Signal's client as well. When you're sending unsecured texts, you get a single checkmark when you send it; when you are sending encrypted messages, a lock symbol and a single check when sent, and a double check when received.

Except that the obvious interpretation of the second checkmark not appearing is that the message was never received, not that it was decrypted by an attacker. Especially when there's a key change warning afterwards. I think this is still the correct interpretation in Signal proper, but who knows at this point?
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