Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

WTF is a KDF?

blog.dataparty.xyz

Post reply on HN
Print view View original

81–90 of 98 posts

Re: WTF is a KDF?

#81

Post by doodlesdev »

zokier wrote: post #61
doodlesdev wrote: post #23

Earlier quoted context omitted.

The problem is PBKDF2 isn't as memory intensive, it's really easy to parallelize on a modern GPU thus making it a much worse PBKDF than Argon2id. Increasing iteration count is just a bandaid over this problem, you also need to have control over memory usage.

Sure argon2 is better, but high iteration count pbkdf2 is still a lot of work to crack, and afaik the work still scales linearly with iteration count. Lets do bit of reality check here. I checked my 14 year old laptop luks setup and it has iteration count set to 462093 and it unlocks near instantly. Looking at hashcat benchmark results for PBKDF2-HMAC-SHA1[1] I'd estimate that for that iteration count it'd do about 4…

No, I agree with you on that matter, there is no reason to panic, I was just trying to explain why Argon2id should receive preference over PBKDF2. Something else I forgot and a sibling comment touched upon is that hashing algorithms that are not memory-intensive can often be run on ASICS and that's when things can get a bit uglier. Overall, this kind of thing really just depends on your threat model and the data you're trying to protect, let's not forget https://xkcd.com/538/ lol

Re: WTF is a KDF?

#82

Post by chaxor »

mr_mitm wrote: post #32
jeroenhd wrote: post #28

Earlier quoted context omitted.

Until we know his password, we can't know for certain. "Fuck the police!2023" fits the description of the password but it's hardly unguessable. All we know is the authorities gained access to his drive's key. We probably won't find out how they did it until his trial starts.

Well, we also know they didn't crack a random 20 character password. But some people appear to be panicking as if they did.

At some level it's extremely likely that this is all that ever needs to be done, even if the password needed to be cracked is 300 characters long and completely random. The likely case is that this password is in a password vault, which is either 1) online managed by a company (in which it's easy to see that it's inevitable to be leaked or cracked, given the news we've seen from these companies) or 2) it's on a local device and still has a simple password to get access to all passwords. It's extremely unlikely that someone has a completely random password that is >40 characters long for the password manager.

Re: WTF is a KDF?

#83

Post by chaxor »

motohagiography wrote: post #51

While I haven't worked on LUKS, if you put aside using several millions of dollars in raw compute, the options are in order of likelihood: - recovering the key from a deleted file, ram, or other caches. - obtained key or bytes thereof by prior surveillance. (so many ways) - a forensics company could be sitting on a LUKS zero-day the way certain companies sit on Signal and iPhone vulns and use them on behalf of state…

... you definitely don't need "GPT" to make a word list...

C'mon guys.

Re: WTF is a KDF?

#84

Post by tptacek »

For whatever it's worth --- probably not much if you don't do any cryptography engineering --- the definition provided here is of a password KDF. There are other important kinds of KDF, and they don't necessarily have the goal of stretching an untenably low-entropy secret into a facsimile of an actual key. HKDF, for instance, is often the way you extract keys from a Diffie-Hellman exchange.

Re: WTF is a KDF?

#85

Post by Gordonjcp »

motohagiography wrote: post #51

While I haven't worked on LUKS, if you put aside using several millions of dollars in raw compute, the options are in order of likelihood: - recovering the key from a deleted file, ram, or other caches. - obtained key or bytes thereof by prior surveillance. (so many ways) - a forensics company could be sitting on a LUKS zero-day the way certain companies sit on Signal and iPhone vulns and use them on behalf of state…

You missed out "handed over key to the authorities and now wants to walk the situation back a bit and pretend he didn't"

Re: WTF is a KDF?

#86

Post by shakow »

flangola7 wrote: post #50
Closi wrote: post #47

"An activist imprisoned in France" makes this sound like some sort of locked up protestor, rather than someone that set fire to a load of vehicles and a warehouse. It should really read "An arsonist imprisoned in France".

Those aren't mutually exclusive. France isn't known for having neutered nonviolent protests like those in the US and UK.

> France isn't known for having neutered nonviolent protests

It definitely is.

Re: WTF is a KDF?

#87

Post by matheusmoreira »

mr_mitm wrote: post #13

It really annoys me how everyone takes that statement that a 20 character password has been cracked at face value. If it was randomly generated, it is physically impossible to crack even if it was hashed with MD5. It's also unlikely that somebody memorized 20 random characters. It is much more likely that the passphrase was weak because it's the title of a Wikipedia article or contained in some public word list. Also…

> the password is more than twenty characters: letters, numbers, punctuation marks

Was it random, though?

Re: WTF is a KDF?

#88

Post by D13Fd »

mock-possum wrote: post #75
mr_mitm wrote: post #45

Earlier quoted context omitted.

Not mathematically, but physically. You need astronomical quantities of energy. Bruce Schneier pointed this out in "Applied Cryptography" (1996): https://www.schneier.com/blog/archives/2009/09/the_doghouse_... (unfortunately the exponents are not displayed correctly here) > One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To record a…

They could have gotten lucky of course.

Yeah this person is saying “impossible” when they mean “extremely improbable.”
Post reply on HN