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It is a security flaw; it's probably not a backdoor. The flaw is as follows: I'm trying to send you a message, but your phone is offline and lost. When you get
by Ar-Curunir 10y ago
It is a security flaw; it's probably not a backdoor.
The flaw is as follows: I'm trying to send you a message, but your phone is offline and lost. When you get a new phone, your key has changed, but WhatsApp will deliver my message before informing me of the key change. This applies also to calls and such (which shouldn't be "delivered" if the other person is offline).
Why could this be bad? WhatsApp could exploit it as follows (maybe under orders from the govt.):
1) Make it seem like a user lost their phone.
2) Wait for a message to be delivered to the user's account.
3) Bring the user back online with a new key (generated by WhatsApp themselves).
4) Read the "encrypted" message.
It's a real vulnerability in the protocol, but the severity depends on your threat model. As I said above, this might be an acceptable trade off for messaging, but not for things like calls, where if the user is offline you don't want the call to go through anyway. All this has been pointed out clearly by the student who discovered it.
- idlewords 10y agoIt's a security/usability trade-off, not a flaw. Making Signal show white-on-white text would make it more secure against attackers reading over your shoulder. So why doesn't Signal do that? These are legitimate trade-offs that the Guardian is portraying as vulnerabilities.
- Ar-Curunir 10y agoYou're being facetious here with the strawman; this is clearly a choice in the protocol that exposes something that is not exposed by, say, Signal. Even if it is a deliberate choice, it doesn't necessarily make it not a flaw; as I said, it depends on your threat model. Anyway, I don't think it's a reasonable choice. How any times do people change phones?!? Even if you're rich you don't do that more than once a year. It doesn't happen often enough for the user to become "accustomed" to warnings and simply click through them.
- idlewords 10y agoI'm not joking here, or making a strawman argument. You could make Signal show white-on-white, so the recipient had to select text to see it. But you don't, because shoulder surfing is not the threat model for Signal. And individually targeted MITM attacks by governments that can take over a server are not the threat model for WhatsApp.
- admax88q 10y agoWhat's the point of E2E encryption if MITM attacks are not in the threat model?
- CiPHPerCoder 10y agoThe point of WhatsApp isn't E2E Encryption. The point of WhatsApp is reliability. The E2EE was an extra. If it even works to enhance the privacy of 0.1% of users, it's helped a million people in ways that SMS has not.
- admax88q 10y agoAdding E2E encryption and advertising based upon that if you're not taking it seriously is a disservice to the users.
- RodericDay 10y agoYou know, I've always liked your writing a whole lot. However your behavior in reaction to this story seems bizarre to me. I see all these people come in defense of WhatsApp using bizarre statistics about domestic violence (big correlation with hacking?). Then someone (tptacek?) was going around saying not a single crypto expert disagrees with their consensus (trucking all over the original source, Tobias Boelter). Then there are all these jokey "Is WhatsApp Backdoored Yet?" expressions. It's a frenzy. There seem to be a whole bunch of people who take The Guardian article as "omg, after this article, people will drop WhatsApp and use something like Messenger instead!". Which, sure enough, maybe a common scenario, and worse. However, the article was obviously meant to push people outside of Facebook gardens, and into a more secure alternative. It's supposed to make you go "WhatsApp is unsafe, I will use Signal instead". One of those "trade-offs" you're talking about in the first place, just like the security vs. purity one. In this case, erring on the side of activism. As a sideline observer with very little crypto knowledge, I think Boelter presented an interesting case, while the anti-Guardian crowd reacted like crazy people, pulling fire alarms, hurling insults, and Streisand-effect-ing the story into a huge controversy. I mean, the EFF article itself, in defense of WhatsApp and against The Guardian, says: https://www.eff.org/deeplinks/2017/01/google-launches-key-transparency-while-tradeoff-whatsapp-called-backdoor https://www.eff.org/deeplinks/2017/01/google-launches-key-tr... > If you are a high-risk user whose safety might be compromised by a single revealed message, you may want to consider alternative applications. As we mention in our Surveillance Self-Defense guides for Android and iOS, we don't currently recommend WhatsApp for secure communications. It goes on to qualify this statement by saying that's a rare threat model. However, that right there, is enough to justify the original piece. The idea, I think, is that everyone should be on something like Signal, so that merely using Signal wouldn't be taken as a reason for suspicion. If you disagree, your argument could surely be better than jokes about white text. Just my two cents as a nobody.
- baybal2 10y agoif a company can snoop your messages on an "encrypted" channel, it is a vulnurability. silly lamer
- Ar-Curunir 10y ago? I'm not defending WhatsApp...
- sctb 10y agoPlease comment civilly and substantively on HN or not at all, and please leave name-calling out altogether. https://news.ycombinator.com/newswelcome.html https://news.ycombinator.com/newswelcome.html https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- zeveb 10y agoHow far does one push that, though? Shouldn't a secure mode go pretty far into the secure side of the security/usability balance? Honestly, would a 'recipient key changed; resend message?' be the worst prompt in the world?
- baybal2 10y agoIt does not depends on a threat model. It works like that: a company sysadmins's being given a rubberhose cryptoanalysis until he compromises company's server. Than, all of that 1bn user r pwned. No company is immune from that: google lost data to a sysadmin who was blackmailed in 2012, facebook regularly fires staff for snooping on users, etc
- anonbanker 10y agoSource on facebook firing snoopers?
- baybal2 10y agoIt does not depends on a threat model. It works like that: a company sysadmins's being given a rubberhose cryptoanalysis until he compromises company's server. Than, all of that 1bn user r pwned. No company is immune from that: google lost data to a sysadmin who was blackmailed in 2012, facebook regularly fires staff for snooping on users, etc