Zxcvbn: realistic password strength estimation • Hacker News Board

Re: Zxcvbn: realistic password strength estimation

#61

Post by eblume » Tue, Apr 10, 2012, 9:48 PM UTC

wh-uws wrote: post #39

I have waited for this for so long. I'm glad someone finally took it up and and more importantly that its on a site as popular as dropbox. (this way hopefully the thinking will gain some traction) Every time I'm forced to have a password with 3 or 4 character classes I sigh and think of that xkcd comic Edit: also try typing the password from the xkcd comic here https://www.dropbox.com/register nice touch

For the lazy, if you enter "correcthorsebatterystaple" the password strength gets set to "lol" with an info-box that reads something along the lines of "Don't take the webcomic too seriously. :)"

Re: Zxcvbn: realistic password strength estimation

#62

Post by [deleted] » Tue, Apr 10, 2012, 9:57 PM UTC

kingatomic wrote: post #60

cellis wrote: post #54

Earlier quoted context omitted.

I just tried my password in your service and here's what I got [0] one quintillion , three hundred ninety four quadrillion , seven hundred seven trillion , thirty six billion , eight hundred fifty one million , four hundred thirty five thousand years to crack. Good god. [0] - 1394707036851435000 translated by http://www.webmath.com/_answer.php

Apparently one of my throwaways is secure nearly until the heat death of the universe. 2.1123066418521704e+73 years to crack

[deleted]

Re: Zxcvbn: realistic password strength estimation

#63

Post by Sidnicious » Tue, Apr 10, 2012, 9:57 PM UTC

FWIW, it looks like Google specifically rates correcthorsebatterystaple lower than similar passwords. I wonder if any of these websites have it in a dictionary?

Re: Zxcvbn: realistic password strength estimation

#64

Post by lowe » Tue, Apr 10, 2012, 10:05 PM UTC

Lagged2Death wrote: post #28

I'm surprised to see that "correct horse battery staple" type pass-phrases really have to be quite long to score well, but that even comically short email addresses ("dlk3@mit.edu") score very highly. In fact, it looks like my ever-so-clever words-and-numbers web passwords ("Happy314Day") are all terrible, but all my email addresses all make maximum strength 4-point passwords. I wonder if that's because email address…

zxcvbn gives high entropy for emails because it isn't matching against them currently. if there's good evidence that people commonly use emails as passwords (and crackers try emails as guesses!) it'd be a great pattern to add.

Re: Zxcvbn: realistic password strength estimation

#65

Post by ig1 » Tue, Apr 10, 2012, 10:13 PM UTC

It's not unlikely that "correcthorsebatterystaple" is in several password attack dictionaries now, so sites may be legitimately ranking it as a weak password.

But more importantly password strength meters don't result in stronger passwords. I saw an analysis a couple of months ago (unfortunately I didn't save the link) where they found showing password strength to the user had no impact on the strength of the password used. People would pick a password and then stick with it regardless of strength advice.

Re: Zxcvbn: realistic password strength estimation

#66

Post by dullcrisp » Tue, Apr 10, 2012, 10:14 PM UTC

Lagged2Death wrote: post #28

I'm surprised to see that "correct horse battery staple" type pass-phrases really have to be quite long to score well, but that even comically short email addresses ("dlk3@mit.edu") score very highly. In fact, it looks like my ever-so-clever words-and-numbers web passwords ("Happy314Day") are all terrible, but all my email addresses all make maximum strength 4-point passwords. I wonder if that's because email address…

"dropbox.com" is ranked Good and "http://www.dropbox.com is ranked Great. I found this amusing, but as it says in the article, there are very many common patterns which it doesn't check and so overestimates the entropy of passwords using those patterns.

Re: Zxcvbn: realistic password strength estimation

#67

Post by shabble » Tue, Apr 10, 2012, 10:21 PM UTC

If these sorts of 'strength checkers' become ubiquitous across enough places, I wonder how much value there will be in using reverse-engineered (most of these are in JS for UX latency reasons, right?) models of their strength testing as another parameter to your brute-forcing module.

Then you can automatically skip any password you know is too simple, because the site won't have allowed the user to set it in the first place. You could also de-weight any constructions your generator is using (keyboard locality, l33t, ..), rather than positively weighting them as is done now.

Intuitively, it seems like the more restrictions placed on a password (must have 1 x char, no more than 20 total chars, ...), the smaller the entire search space. But where is the inflexion point where these rules generate stronger passwords than they assist.

Then again, if you're doing your hashing and storage right, brute force ain't gonna help.

Re: Zxcvbn: realistic password strength estimation

#68

Post by lowe » Tue, Apr 10, 2012, 10:22 PM UTC

DanielStraight wrote: post #38

CGamesPlay wrote: post #34

It certainly needs a rule for putting spaces between the words. "correct horse battery staple" and "correcthorsebatterystable" should be treated as being approximately equal in strength.

Not to mention: horsebattery -- 3 minutes h orsebattery -- 8 years ho rsebattery -- centuries horseb attery -- 85 years horsebat tery -- 54 years Which at the very least is a little odd, even if the reason (breaking up the words into less word-like structures) is clear. Also: abcde -- instant a b c d e -- centuries

zxcvbn's current analysis for 'correcthorsebatterystaple' vs 'correct horse battery staple' looks about right to me, it's counting each space as an extra bruteforce character.

horsebattery vs 'h orsebattery', on the other hand, shows a clear flaw -- it doesn't tolerate misspellings up to a given edit distance. edit distance is tricky because efficient word segmentation gets much harder, especially w/ support for l33t substitutions.

'abcde' vs 'a b c d e' is tricky too. i could add special case for spaces only that would allow zxcvbn to recognize 'a b c d e' as a sequence, but it wouldn't cover 'a-b-c-d-e', 'a8b8c8d8e' etc.

Re: Zxcvbn: realistic password strength estimation

#69

Post by jamesaguilar » Tue, Apr 10, 2012, 10:28 PM UTC

shabble wrote: post #67

If these sorts of 'strength checkers' become ubiquitous across enough places, I wonder how much value there will be in using reverse-engineered (most of these are in JS for UX latency reasons, right?) models of their strength testing as another parameter to your brute-forcing module. Then you can automatically skip any password you know is too simple, because the site won't have allowed the user to set it in the firs…

When the space of passwords denied by a rule is much, much smaller than the minimal search space, it doesn't matter all that much.

Re: Zxcvbn: realistic password strength estimation

#70

Post by fromhet » Tue, Apr 10, 2012, 10:33 PM UTC

ig1 wrote: post #65

It's not unlikely that "correcthorsebatterystaple" is in several password attack dictionaries now, so sites may be legitimately ranking it as a weak password. But more importantly password strength meters don't result in stronger passwords. I saw an analysis a couple of months ago (unfortunately I didn't save the link) where they found showing password strength to the user had no impact on the strength of the passwor…

May be true, but they are not ranking it as a weak password because it exists in crackers databases but because it doesnt contain numbers and special chars.