Comment by madmod | Hacker News Reader

Comment by madmod | Hacker News Reader

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I understand that the info to answer my question may not be public yet. I would greatly appreciate an an answer by someone who can explain when it is.

If an attacker had recorded encrypted WiFi traffic in the past and then performed one of these attacks could they see the traffic? (I know TLS is used for a lot of traffic, but in time that will be broken too.)

It seems to me that a patient attacker could gain a lot of sensitive info given enough time. Is this assumption flawed? I would love to hear why/why not. (Nonces make decryption of large amounts of TLS traffic impractical?) What about the impact of just knowing DNS lookups? (Real world info on DNS caching? Does DNSSEC stop this? Is it widely implemented?) What if a data broker recorded a lot of encrypted WiFi traffic at a public place like a mall? (Could they learn MAC addresses? mDNS device names? DNS lookups? I bet a lot of tracking cookies and other advertiser tokens don’t bother with TLS which could get them emails and more.)

Someone recording encrypted WiFi traffic from a sensitive network may have enough motive to do something this long-term and the attack would be (electronically) undetectable. Most people rarely change their passwords and at a minimum this would give an attacker knowledge of the internal network, intranet sites, and services used by targets.

I expect they could, yes; WPA2 doesn't offer forward secrecy.

But WPA2 never offered much anyway. If you're on mall wifi, you can already see unencrypted traffic for everyone else, because the client keys are derivable from the shared passphrase (which presumably everyone at the mall has been told) and overhearing the four-way handshake when someone joins. And! You can even fake a disconnect message that forces the four-way handshake to happen again, if you weren't around when the client originally joined.

All of which is to say, WPA2 in passphrase (PSK) mode never actually provided meaningful encryption against other people on the network. :( Someone forgot to tell the protocol designers that Diffie-Hellman exists. Using Diffie-Hellman would achieve both removing the exploit where you observe the four-way handshake, and providing for forward secrecy too.

> * If you're on mall wifi, you can already see unencrypted traffic for everyone else*

Without contradicting your observation, I want to mention that virtually anything important you do on the Internet these days--from online banking to Google searches to reading Hacker News--is protected by a second independent layer of encryption: HTTPS. I'm not excusing the WPA2 flaws, but I do think that your bank info, web searches, and Hacker News comments are secure even at the mall.

If someone can offer a credible explanation of why online banking or other HTTPS activity is insecure on public wifi, I'd like to hear it please.

If you don't have extensions that force HTTPS on all content, you could, for example, get served a malicious image file.

from the article:

> they won’t be able to pretend to be a secure site like your bank on the wifi, but they can definitely pretend to be non-secure resources

You're right, though you're being a little rose-tinted about the situation. I think amazon.com shopping turned on redirects from HTTP to HTTPS last year sometime -- before that they would even redirect from HTTPS to HTTP. That means that until last year, in most instances, your coworkers or your fellow coffee shop customers could see which items you were considering buying online on Amazon. That's really, really bad!

Also, HTTPS doesn't protect domain names. If you're making TLS connections to (e.g.) a porn site over WiFi, the other people sharing your connection don't need to decrypt your traffic to know what you're doing.

Update: It looks like the General answer is no, these attacks require interaction with the client at the time of exploitation to defeat the crypto. (I could be totally wrong however as I don’t understand the crypto.)

Update 2: Apparently anything captured along with the device handshake can be decrypted after the fact if the attacker learns the password used at that time. (Source: https://www.google.com/amp/s/mrncciew.com/2014/08/16/decrypt...) So to decrypt all traffic an attacker would only need to compromise any machine which has the password saved. (Assuming they see the handshake for the device connection.) This indicates that regularly rotating the password (To something unpredictable) has some limited value.

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