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WTF is a KDF?

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Re: WTF is a KDF?

#71

Post by kazinator »

dmix wrote: post #68
kazinator wrote: post #62

> Earlier this week a letter from an activist imprisoned in France was posted to the Internet. And this letter's authenticity was verified how? Even if authentic, it could be the result of coercion, to create a bluff and spook some other activists. Or it could be that the cops fooled the activist into believing that they cracked his hard drive, so that he then wrote the letter. Do not believe everything "posted to th…

This sounds a bit paranoid. You give the police too much credit. Lying to the public to scare off people from using Linux encryption?

Might you be confusing skepticism with paranoia? They are almost opposite: the paranoiac is too willing to believe; a skeptic can be too unwilling.

Police perpetrating bluffs on people they have in custody is standard operating procedure.

I wouldn't weave the "scare people from using Linux encryption" narrative into it, though; I don't think that would be their motivation. (Though it could be a counterproductive unintended effect. The last thing authorities want it spooking people into finding better encryption.)

Anyway, I suspect that in situations in which cops really crack someone's hard drive at great expense, it mostly behooves them to take advantage of whatever they learn, while keeping secret how they got it.

If you have someone in custody who thinks their hard drive is safe, while you have secretly cracked it, that gives you an information advantage you can use at a strategic time.

Re: WTF is a KDF?

#72

Post by jadtz »

alsobrsp wrote: post #60
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…

> It's also unlikely that somebody memorized 20 random characters. I routinely memorized 15 character random passwords until I switched to bitwarden, 20 doesn't seem out of bounds. Now, with bitwarden, I have no idea what any of my passwords are.

So now you only memorize one 15 character random password for your bitwarden, is this the way to go? I am new to password managers.

Re: WTF is a KDF?

#73

Post by giantrobot »

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…

I think it's worthwhile to be concerned about hashing ASICs used in crypto mining. They're stupidly cheap and outperform GPUs for hashing. They don't have much in the way of memory so they're not useful in memory-hard problems.

Re: WTF is a KDF?

#74

Post by mock-possum »

jadtz wrote: post #72
alsobrsp wrote: post #60

Earlier quoted context omitted.

> It's also unlikely that somebody memorized 20 random characters. I routinely memorized 15 character random passwords until I switched to bitwarden, 20 doesn't seem out of bounds. Now, with bitwarden, I have no idea what any of my passwords are.

So now you only memorize one 15 character random password for your bitwarden, is this the way to go? I am new to password managers.

That’s the idea yeah - you have one long high entropy password that you use to unlock all your others. Then you only need to remember one thing.

In my case, this isn’t my literal password, but it’s very similar to: “These420HugeWhiteBadgers1984” Which is secure enough, easy to enter, and easy to remember.

Re: WTF is a KDF?

#75

Post by mock-possum »

mr_mitm wrote: post #45
Aeolun wrote: post #38

Earlier quoted context omitted.

You know this because you think it is mathematically impossible?

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.

Re: WTF is a KDF?

#76

Post by [deleted] »

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…

[deleted]

Re: WTF is a KDF?

#77

Post by medo-bear »

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".

> "An arsonist imprisoned in France"

this is not factual as arson is an accusation

Re: WTF is a KDF?

#78

Post by ipython »

wood_spirit wrote: post #57
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…

Also, I would expect the government can crack passwords more cheaply than hiring normal commercial cloud compute. Everything from negotiating good prices, to having their own or reserved cloud so the cost is having the ability to do it more than actually doing each crack, to asking an ally for help. Would be kinda shocking if they pay the sticker price for this stuff.

You’re right. They probably pay a premium on the sticker price, after you include all of the necessary professional services and us gov only personnel with security clearances.

Re: WTF is a KDF?

#79

Post by aspectmin »

Recognizing the ability of these entities to hire great cryptographers, what’s the possibility they found a shortcut or vulnerability in the algorithm (or set thereof) itself?

Re: WTF is a KDF?

#80

Post by rlpb »

eternalban wrote: post #70
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…

> even if it was hashed with MD5 This is what I don't understand about articles like this. Say we're using a cryptographic hash to generate the password from even a commonplace phrase. Typically you will have thousands of random bits in the hash and you can grab a uint64 (or even a uint128 if you want) from anywhere in that (theoretically uniformly distributed) set of bits. Is that not a random point in a 2^64 (2^128…

No, because in that entire space, only eg. 62^20 would be used, and that's a much smaller space. There are various techniques to focus on that subset of the space.
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