Comment by Strom | Hacker News Reader

Comment by Strom | Hacker News Reader

There's no need for theoretical chat history leaks, there's already a practical one in place. Online WhatsApp backups aren't encrypted with end-to-end encryption. [1][2] WhatsApp keeps being "helpful" and aggressively suggests users turn on online chat backup, without mentioning on the same screen that this means your chat history will be uploaded without end-to-end encryption. The history is encrypted with a key that is sent to WhatsApp servers. This is used to provide a passwordless backup restore function even when you lose your phone. You contact WhatsApp with your mobile number and WhatsApp sends you back a code that is used to derive the key that was used to encrypt the backup which was sent to Apple/Google.

All of this makes Zuckerberg's claims that law enforcement can't read the messages because Facebook can't pretty misleading. Law enforcement could get the backup from Apple/Google and the key from WhatsApp and have access to the whole chat history. There are apps already available to help you through this process. [3]

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[1] Media and messages you back up aren't protected by WhatsApp end-to-end encryption while in iCloud. https://faq.whatsapp.com/en/iphone/20888066/

[2] Media and messages you back up aren't protected by WhatsApp end-to-end encryption while in Google Drive. https://faq.whatsapp.com/en/android/20887921/

[3] Elcomsoft Explorer for WhatsApp 2.30 can now download and decrypt Android user’s encrypted WhatsApp communication histories https://blog.elcomsoft.com/2018/01/extract-and-decrypt-whats...

There is another, even more direct route that works regardless of backup settings: WhatsApp already includes a backdoor that allows it to decrypt all messages and send them to Facebook servers, conditioned on a single UI authorization from the user, specifically scanning a QR code on https://web.whatsapp.com/

Once the terminal is authorized, the backdoor channel is opened in perpetuity and there is no more interaction with the user, it could happen at any time on your phone and you have no way of knowing short of complex reverse engineering of the app or network stream.

And there is absolutely nothing stopping Facebook from inserting code into WhatsApp to skip the UI prompt when initially setting up the back channel, it would be a few lines of code. With Google or Apple's collaboration, a suspect's terminal could be surreptitiously updated to a vulnerable version that could open the channel, then updated again to the stock version, all in a matter of minutes, allowing law enforcement perpetual access to the stream of decrypted data. It's likely NSA has sufficient private key material to orchestrate something like this without any collaboration.

The (not) news here is that any end-to-end encryption scheme is just a way to thwart packet sniffing hackers and telcos, and it has no effects on the providers themselves, you still need to trust their binaries. Open source and audited open repositories were never more relevant.

Asking as a layman unfamiliar with security jargon, do you mean to say that if I ever log in on Whatsapp's web interface, even once, then my Whatsapp app and the messages are backdoored?

Technically the key should never leave the web UI (and be discarded once you close the page); but since they control the domain & what they serve, they could serve a malicious version of it that silently exfiltrates that key back to them which they can use later on even after you close the page.

The most telling evidence for me was that Signal was banned in Russia because the government couldn't read their messages, while whatsapp was just fine.

Wrong signal thou, the right one is that WhatsApp haven't been banned while being the most popular in a country.

Even though I also find it very suspicious that WhatsApp keeps proactively badgering me about turning backup on, I don’t see how this could be exploited by Facebook as the messages are stored in iCloud and Google Drive which it can’t access.

Whatapps needs a Google Drive API token to write that backup, don't they? If so, surely they can read it using the same token?

Would there be any way for a user to see if/when the token has been reused? Doubtful but perhaps Google provides (or could provide) some kind of log similar to how Facebook lets you view Active Sign Ins and Sign In history.

Once it has been used, it is too late. This insight would therefore not be a solution to the problem.

My assumption was that the data gets handed off to Google/Apple functions on your phone that handle backups. Could anyone confirm?

You can just disable cloud backups, no?

Not exactly, as the other side could just back it up instead. You also need to make sure that the people you communicate with never misclick OK on the constant backup advisory popups.

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