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More details in "WhatsApp Retransmission Vulnerability" [1] from April last year. [1] https://tobi.rocks/2016/04/whats-app-retransmission-vulnerab...
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"Signal is bad as explained previously, it requires Google on your phone to even work. If you think Google is more trustworthy than Facebook, sure go ahead and just use Hangouts or whatever." Every time Signal comes up on HN people make this point (Signal is bad) as if it is true. And every time it is exposed as bs.
A legitimate criticism is that they make it hard for people who don't want to use play services to user their app. For the privacy of the messages themselves, google really cannot interfere, unlike WhatsApp/Facebook.
No matter what IM service you use: As long as they manage the public keys for their users, they will be vulnerable to exactly this problem. This isn't just WhatsApp. This applies to iMessage and Signal too. In all cases, we rely on the word of the service provider that they don't sneak additional public keys to encrypt for into the clients and in all cases we hear that doing so would cause a message dialog to appear,…
I think it would be wrong to start complaining about other apps. We don't know of vulnerabilities in other apps. We DO know of one in WhatsApp. Let's focus on what we know and take WhatsApp to task on it instead of wasting energy on what we don't know.
Doesn't this mean that only subsequent messages can be decrypted? i.e. Whatsapp has provided forward secrecy (as long as they haven't been using this trick from the initial secrets that were set up)?
Pretty sure that is the case. the key is changed while you're offline making any unsent messages use the new key that they know. But if they can change the key while you're offline that means they can change the key and know everything from that point on.
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The fact that you have a PhD in cryptography doesn't necessarily mean you know how to write secure code. Especially C code. Lot of people hated OpenSSL quality long before Heartbleed, but it took that vuln for people to actually realize how bad it is. I can imagine a good, secure SSL library being written by somebody without a PhD, in a safer language.
I'm not sure that security is fully correlated with the degrees held by developers. It seems to have more to do with their motives. WhatsApp is owned by Facebook, which is wholly motivated by profit and the aggrandizement of Zuckerberg, not by providing secure code. What's most interesting to me is that for all the people who complain that C is insecure, I don't see any great, proven open source crypto implementation…
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So, just to clarify my understanding: Basically, what we have here is a weakness in the client , namely a provision that allows the server to send the client a fresh key and ask for re-encryption and re-sending with the new key. This, in turn, would allow for a good old MITM attack if the server were to be compromised. This re-encryption and re-sending of messages would be without intervention by the user, though a m…
Aren't all messages undelivered, until they are?
if you had verified fingerprints with Bob and are happily chatting with him, all the messages that reached him (two tick marks in WhatsApp) are safe.
Only those that have not yet been delivered (one tick mark) would, when the server sends you you a new key, be re-encrypted and re-sent.
All of this, as usual, is predicated on the client behaving as promised.
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As I mentioned in my comment, any exploit that can only be performed by the server is essentially irrelevant as we already can't have perfect trust in the server. edit: I'll respond to everyone as I worded this poorly. What I mean is that an attack that can only be performed by Facebook/WhatsApp(depending on if you believe they are kept separate) is mostly irrelevant as they could always push an update to the App/Pla…
We can't have perfect trust in the server, so this feature being supported by the client breaks the security guarantees of WhatsApp's E2E encryption.
"Asked to comment specifically on whether Facebook/WhatApp had accessed users’ messages and whether it had done so at the request of government agencies or other third parties, it directed the Guardian to its site that details aggregate data on government requests by country." This is why people should try and use Signal instead of WhatsApp. You can't trust Facebook to care about your privacy.
Signal is bad as explained previously, it requires Google on your phone to even work. If you think Google is more trustworthy than Facebook, sure go ahead and just use Hangouts or whatever. We cant have nice good encryption and safe communication when geeks push this Signal onto unsuspecting users, when the real option is to keep improving Tox.Chat and bitmessage.
The key part is this, and it was apparently reported back in April 2016 with Facebook replying it's "expected behavior", it's not something a general attacker can do but it would enable WhatsApp/Facebook to read conversations: > WhatsApp has the ability to force the generation of new encryption keys for offline users, unbeknown to the sender and recipient of the messages, and to make the sender re-encrypt messages wi…
I don't think this is as serious as it seems, this exploit only applies to undelivered messages, which granted is not great, but is at least something. And any WhatsApp update could potentially include code to snoop on decrypted messages so exploits that can only be performed from the WhatsApp server side - i.e the example in the article about snooping entire conversations - are not really that relevant. Having said…
> Boelter said: “[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 users might not notice. Using the retransmission vulnerability, the WhatsApp server can then later get a transcript of the whole conversation, not just a single message.”
In other words, what seems like "a vulnerability that only affects some messages" could be turned into a full blown interception capability with very little change.
Some more background: This was presented in the lightning talks at 33c3, starting around minute 48: https://media.ccc.de/v/33c3-8089-lightning_talks_day_4 Here's the congress wiki with some more links: https://events.ccc.de/congress/2016/wiki/Lightning:A_Backdoo... And a blogpost: https://tobi.rocks/2016/04/whats-app-retransmission-vulnerab...