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Jun
22
comment Trying to keep high school students out of the Wi-Fi network
Do note that preventing Wi-Fi access does not fundamentally solve the underlying problem of students having internet access: they can still use a mobile data plan. So on that front it's a lost battle, and should perhaps not even be a goal of this exercise.
Jun
20
comment Does verifying identity by positions in passwords mean passwords are stored unhashed?
@JeffMeden Yes but from the cryptographic perspective that's equivalent to "passwords are stored unhashed": the website operator has enough information to cheaply recover the original password, which means they are able to leak enough information for an attacker to do the same. So not much different to storing the password encrypted and hoping that only the database leaks and not the key(s).
Jun
16
comment Does a leaked LastPass hash enable the attacker to retrieve encrypted passwords (ciphertexts)?
OK I now understand that this scenario is implausible. LastPass would be silly to simply compare the hash they receive against the hash they store. I imagine what actually happens is: master password is hashed client-side. Hash is sent to LastPass. The hash is then hashed with those server-side 100k rounds. The result of that is compared to the database that leaked. Therefore to obtain encrypted passwords, the leaked hash is insufficient, and would be very difficult to crack within the window of opportunity that has now been closed.
Jun
16
comment Does a leaked LastPass hash enable the attacker to retrieve encrypted passwords (ciphertexts)?
Surely it must hash the password client-side before performing authentication, because they cannot send the password itself (that's part of the promise: they don't know your master password). But I see a way out now: client sends a hash, server hashes it with 100,000 rounds and compares that against the stored hash. This makes my entire question redundant. I think I should close it.
Jun
16
comment Does a leaked LastPass hash enable the attacker to retrieve encrypted passwords (ciphertexts)?
"Under those conditions, if an attacker was able to crack a user's master password" - but my question is whether with the leaked hashes they could retrieve the (encrypted) database without cracking anything, or perhaps by hacking only the client-side hashing rounds, of which there are significantly fewer.
Jun
16
comment Does a leaked LastPass hash enable the attacker to retrieve encrypted passwords (ciphertexts)?
This relies on them being able to distinguish legitimate requests from attackers' requests. They may or may not be able to detect a well-planned attack where a large botnet is used to pull the ciphertexts slowly.
Jun
16
comment Does a leaked LastPass hash enable the attacker to retrieve encrypted passwords (ciphertexts)?
@MikeOunsworth Unfortunately all the information I have comes from the LastPass blog post, and they don't specify how long it was between the leak and the time when they started requiring new IPs to verify by email.
Jun
14
comment NFC contactless payment security
I'd argue that it should be up to the user at which amount they are prompted to enter a pin. I'd set mine to zero to be prompted for every payment. NFC + pin would still be vastly faster than the current card payments in Europe. They are slow not because of the pin! They are slow because you wait and wait until you are even prompted for a pin, and then you wait some more afterwards.
Jun
10
comment Does a WPA2-PSK authentication only succeed if both parties know the pre-shared key?
@SilverlightFox by "non-existent" I'm only pointing out that it's not available, otherwise it looked like it could raise people's hopes up. I've rephrased slightly.
May
21
comment HTTPS in captive portals and the Apple Captive Network Assistant
@Iszi over HTTPS after verifying the EV certificate to a company I also trust with my credit card at home - sure, why not? I'd love to authorize a one-off payment instead, but alas credit card systems aren't quite there yet.
Apr
20
comment Are cars with keyless proximity-based entry protected against range extenders?
The paper linked in the other answer has demonstrated the attack in multiple cars, so the part of this answer that states it's not practical yet appears to be false.
Apr
20
comment Are cars with keyless proximity-based entry protected against range extenders?
That's a very good paper that addresses exactly this question. Thanks!
Apr
19
comment Are cars with keyless proximity-based entry protected against range extenders?
I'm guessing the close votes are because car entry doesn't sound like IT security. It seems very similar to me to NFC/RFID security, which appears to be on topic, but if the community disagrees, by all means close this.
Apr
18
comment What prevents people getting charged over NFC in crowded places?
I'd go for a system that requires me to simply press a button on the card while it's being processed. Just to confirm that someone is physically in possession of the card and intending to pay with it. This would preclude anyone charging me when it's in my pocket, without requiring a pin. A reasonable trade-off maybe?
Apr
15
comment What is a good algorithm for memorizing a password in a few minutes?
The way our memory works for things like that makes it impossible to remember something like this for a long time. You have to repeat it at certain intervals for it to stick. No way around it other than avoiding to have to remember something in the first place (like some answers suggest).
Apr
15
comment Why does the user pick the password?
The problem with the password manager approach is that either you only have it on your main computer, or you trust a third party with all of your passwords (at least that they have the right crypto). I've not managed to overcome the fear of letting some sync service sync my passwords to everything.
Sep
24
comment Why are web servers ubiquitously configured by blacklisting inaccessible files instead of whitelisting the accessible ones?
@Iszi harder than maintaining security-hole-free blacklists? As someone who has made and maintained both, I have to disagree.
Sep
8
comment Can I scratch off the magnetic strip off a debit card to only allow chip and PIN?
What @tylerl said, because otherwise you wouldn't be able to use the card online. Having said that, we really need to fix this, e.g. with 2FA (e.g. send a text message that requires a respone for card-not-present transactions).
May
8
comment What risks are introduced by the browser passing the “referer” to the next site visited from a link to another domain?
A privacy fix would not have to break this: the Referer header could still be supplied if the destination is on the same domain.
May
7
comment What risks are introduced by the browser passing the “referer” to the next site visited from a link to another domain?
For the record, this is no longer the question I asked; it's been edited and became a different question.