Zoom’s encryption has links to China, researchers discover
theintercept.com
theintercept.com
Matthew Green's article is being discussed here: https://news.ycombinator.com/item?id=22771193
https://citizenlab.ca/2020/04/move-fast-roll-your-own-crypto...
At the very least, they are validating TLS certificates. (Which I know is the true bare minimum requirement of TLS, but "goto fail" and all...)
>We set up mitmproxy to intercept the TLS traffic and configured the Zoom Linux client to route its TLS traffic through mitmproxy. Fortunately, the Zoom client did appear to warn us that the fake TLS certificates generated by mitmproxy were untrusted.
Deterministic encryption can be ok if the data that you’re encrypting is already really random (high min-entropy). Compressed audio and video streams have a decent amount of entropy. Probably not enough to satisfy a cryptographer, but it’s probably enough to make it very difficult to learn much from 128-bit AES ECB blocks.
Note that everyone’s favorite ECB example with the picture of Tux the Linux penguin is not very realistic, because the plaintext is not compressed. If you ECB a JPEG or a PNG, you won’t see the same patterns.
I teach the attacks on ECB in my network security class. It’s bad, but AES is not the Caesar cipher. I’m not sure “trivially broken” is quite right.
That said, I am really curious what Zoom is actually doing here. Going to have to take a look today. My guess is that the real fail from using ECB mode is more likely to come from using it on audio/video metadata, or on other more structured parts of the protocol.
Yes, it's objectively worse than literally any other AES mode. You wouldn't need to depend on compression to protect your data.
Any deterministic encryption relies on entropy of the plaintext for security [2]. This is not unique to ECB.
My objection was to the hyperbolic phrase "trivially broken." SIV mode is deterministic, but nobody who understands what it does would call it "trivially broken."
And I'm definitely not saying that anyone should use ECB. Just that in this case, the vulnerability may not live up to the hype.
By all means, go ahead bashing on Zoom. It's the cool thing to do these days, and clearly they've done enough to deserve most of it.
If Zoom had a security audit, the auditors would quickly suggest using either some sort of ECB-based algorithm that uses an SIV, or just AES-CTR. I'm guessing they went with ECB due to its parallelization of the encryption/decryption process, which totally makes sense, except that there are much more secure algorithms out there.
Yes, that is the question here, and it's a really fascinating one. How often do you send two identical 128-bit chunks in practice? How much does it depend on the quality of your webcam and your lighting? If the video is grainy and splotchy in the background, you're getting a lot of randomness in your data. How much does that help? Any at all? Or are you still totally screwed?
> even if it is, why chance it when you can use CTR mode and a random nonce, with practically zero overhead?
1000 times this. Crypto code should be like the safety components in a car or an airplane. You wouldn't buy a car with seatbelts or brakes that work 90% or even 95% of the time. In the same way, you shouldn't write network code that probably doesn't let an adversary figure out everything you're sending.
How do they keep doing this? Do they just put whatever sells best in the documents and implement something else? First the end2end thing, now 128 instead of 256 bits. How many more are we going to find in the coming days?
Hard to say. Could be cultural where sales and engineering butt heads. Could be "sell it first, develop it later so we can beat the market" mentality.
Either way, Zoom is going to go down as either a company that did everything right and won the market or did everything wrong and won the market. Depending on who you talk to.
Yes.
I've always expected businesses to stretch the truth with their marketing e.g. "Leading Brand of Donut in America", "Award Winning Bread", "Cheapest Gas for 50 miles"
However Zoom are just engaging in straight up false advertising regarding security features. It's not cheeky -- it's wrong.
I've worked 10+ years in Silicon Valley and the motto "it is better to beg forgiveness than ask for permission" really does ring true. This manifests at all levels from ICs and up the chain of leadership. People do what gets them their bonus/promotion and everything else be damned. "Acquire the customer and fix the security problem later" was the mindset here.
In addition to letting the Chinese (and possibly US) government in on the encryption keys, the encryption scheme is also badly broken (ECB mode of AES). Prof. Matthew Green has written many articles about AES and encryption more generally and I recommend his blog if you are interested (even as a lay person).
https://blog.cryptographyengineering.com/2011/12/01/how-not-...
[edited for typo]
(In minor defense of self, I should have said CBC or "later").
* from internet or from old codebases of one’s company
Does anyone else find it really weird? Late-night TV hosts, I can understand - maybe they just get paid for it, or have Zoom shares. But for example UK government leaders repeatedly mentioning it by name, e.g. Matt Hancock saying that despite being unwell, Boris Johnson is still having "Zoom videoconferences", or saying Johnson addressed his "Zoom cabinet", just feels... weird.
Edited to add: thinking about it more, I remember "FaceTime" being used pretty similarly when it was new. So I guess all the bad news is just sensitising me.
It implies speed, and thus implies power.
Since you zoom in on things to see them better it implies attention to detail.
The productivity of the prime minister is in no way hampered, people, he Zooms!
on far too many lenses I've owned it's simply not true
This is a huge win for Zoom on a marketing front.
People then look at the articles written in the media and say "hey i use that app too, cool, we are part of the same tribe".
Showing of knowledge of the tech-zeitgeist is an easy way for a politician or anyone for that matter to appear being both with the times", "tech-savvy" and just the same as regular folk.
Most video chat apps are straightforward once set up on the phone.
Before this sounds anti-immigrant, I'm the product of immigrants like most Americans and I think the qualifier for being American is considering oneself American and having citizenship or on the path to get it.
So “Zoom Us” like “Call Us.”
No pun intended.
That isn't exactly the case, per the same article. More Zoom is choosing a poor choice among other choices, of implementing AES:
"Furthermore, Zoom encrypts and decrypts with AES using an algorithm called Electronic Codebook (ECB) mode, “which is well-understood to be a bad idea, because this mode of encryption preserves patterns in the input,” according to the Citizen Lab researchers. In fact, ECB is considered the worst of AES’s available modes."
Bad idea but not "rolling own crypto bad"
edit: agree it's bad. this is pointing out inaccuracies in language from tech journalism reporting on security. This continues to be an issue per the miseducation it creates for the general public in infosec concepts, which is already an uphill battle of misconceptions. Since these articles, or AG Barr, are the discussions that actually hit the mainstream, it's an issue that needs to correct.ed Tech journalism, a profession focused on 'getting the facts,' are the direct conduit of this version of miseducation/failure of facts, and should be corrected. See: NY Times Baltimore Ransomware = NSA Tool (false), Bloomberg Supermicro (false, so far), etc.
- ECB - CTR
Note that CTR is still recommended for use and is often used for things like hard-disk encryption where random access is required. Furthermore, the only difference between ECB and CTR is that CTR includes an incrementing counter in the input to the encryption algorithm to ensure that each encryption is unique. Do you know what else starts with an incrementing counter? UDP packets intended to form an audio or video stream.
So yes: ECB can be bad, but there's no evidence that Zoom are actually using it incorrectly. Using CTR when you already have a non-repeating data stream would only add overhead and potentially negatively impact the amount of useful data that can be streamed.
Is there any non-repeating data apart from noise (if even)?
Let's assume the counter is at the start of the packet. An AES block is 16 bytes, so the counter ensures the first 16 bytes of ciphertext are unique across packets. But any patterns in the remainder of the packet are preserved, within and across packets.
- misusing cryptographic primitives is one way of rolling one’s own crypto
- ECB really is that bad
I see denial is strong or HN has already it's army of wumaos.
P.S. Personally, I don't consider the NSA having my data as being any better, thank you.
EDIT: Just to be clear, I don't think Zoom's encryption claims should be trusted, but it's not because CHINAAA, it's because they're misleading people into thinking TLS means E2E.
When people say 'the server with the encryption keys is physically located in China, and they have many Chinese employees', the subtext that we should all know at this point is that they're required by Chinese law to turn everything over to the authorities. We have hard evidence & beyond hard evidence of this, so it's kind of assumed that educated people are aware of this. And yes the same goes for say US telecom companies having legally mandated backdoors & the US government exploiting this to conduct unauthorized surveillance or even just purely commercial spying, it's well-documented, everyone should know this. So in the future someone can say 'this telecom company is US-based' and we can all understand the subtext.
So it's OK to just say 'the servers are in China' and we should all know what that means, at this point. TLDR- it's OK to have priors
In their recent post about this question they apologize for what they admit to be an incorrect use of the phrase "end to end encryption". They base this on the existence of things like the gateways used to the regular telephone network.
It seems like an odd way to spin this. Why didn't they just state that the data is encrypted "end to end" and then leave it at that? Apple supposedly has access to the keys used to encrypt FaceTime calls but they happily involve the "end to end encryption" marketing phrase. I don't see why Zoom couldn't do the same. The way Zoom has handled this could of been a lot better.
I think the world needs a consumer standard for cryptography. Something like:
* Level 1 for the case where any eavesdropper can get the plain text.
* Level 2 for when just the provider can get the plain text.
* Level 3 for when just the users can get the plain text.
Most of what is being described as "end to end encrypted" these days is really just level 2 even in the case where the provider does not have the keys due to the fact that the provider can trivially MITM the traffic. The general public should be made aware of the distinction without having to dig into the technical details.
Zoom specifically states that they do not have access to session keys. Apple doesn't even make such a statement.
Apple’s statement is stronger.
However in practice, making public statements like this and breaking them would have enormous reputational costs.
Apple has put up a bigger stake on the truth of their encryption story than anyone else.