logoalt Hacker News

applfanboysbgontoday at 5:13 PM5 repliesview on HN

It's open-source, so just build it yourself with the tiny change. Something this trivial could be done with a 30 second prompt at this point, so there's not even an excuse of "too much effort".

I will note that the XKCD password scheme being proposed there is, in fact, completely insecure. A modern consumer GPU can crack "four random English words" in a day. You can argue that it's the user's choice to be allowed to use insecure passwords, but arguing that that scheme is actually secure is just wrong.


Replies

bilkowtoday at 7:02 PM

> A modern consumer GPU can crack "four random English words" in a day.

Let's run the math:

EFF's long wordlist[0] (the one used by Bitwarden's passphrase generator) has 7776 words, which is about 13 bits of entropy per word (log2(7776) = 12.92). A 4-word passphrase then has 51.7 bits of entropy, meaning there are 2^51.7 possible options for the passphrase, which is 3.66E15 possible options.

For reference, a password with all completely random characters and symbols, for each character you have 70 possibilities, or about 6 bits of entropy. An 8-character completely random password (no words or the usual patterns) then has about 49 bits of entropy, which is less than a 4 word passphrase.

About the time it takes to crack it, assuming you can test an average of 1 password per μs (you probably can't, as passwords are usually stored using key derivation functions[1][2] with work factors tweaked for current hardware) it would take ~116 years to crack it. I usually see 5-passphrase recommended nowadays, which would multiply the required effort by 7776.

Sure, a 16-character random password has a lot more entropy, but it's also a lot harder to interact with (reading, comparing, typing) if you end up needing to, and it's still easier to crack than an 8-word passphrase.

[0] https://www.eff.org/dice [1] https://en.wikipedia.org/wiki/Key_derivation_function [2] https://cheatsheetseries.owasp.org/cheatsheets/Password_Stor...

show 1 reply
tredre3today at 5:34 PM

> A modern consumer GPU can crack "four random English words" in a day. [...] but arguing that that scheme is actually secure is just wrong.

Let me do just that!

This is a networked service. You send your password (or a hashed form) to it, and it validates it. You don't have the local hash to bruteforce it offline.

Even if we only consider the top 10k english words, it's 10000^4. It's going to take years to bruteforce this over a network because you'll go through so many rate-limits, cooldown periods, and outright bans that it's questionable whether it's even possible.

show 2 replies
wavemodetoday at 7:16 PM

> A modern consumer GPU can crack "four random English words" in a day.

This is just completely false.

Fidelixtoday at 7:04 PM

Did you even check what hash they are using?

throwaway27448today at 5:25 PM

> A modern consumer GPU can crack "four random English words" in a day.

Sure, if you can rely on users using a specific format. The joy of the xkcd technique is you don't need to tell other people what yours is.

But, people just aren't going to remember strings of gibberish. Expecting users to do this is just silly.

show 1 reply