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Re:Stop forcing arbitrary password rules by forgotpwtomain on Saturday October 24, 2015 @05:03AM (#10442960)
I agree with the point the author is making and generally am just as annoyed by arbitrary password rules; nevertheless:

> chili dog monkey nutso

Is definitely not 18 quintillion years at best it's approximately 250000^4 which is 2^72.

A good (though still requiring some memorizing effort approach) would be something along the lines of https://github.com/bitcoin/bips/blob/master/bip-0039.mediawi... which uses a standard dictionary of 1626 easily memorable english words with each password being a 12 word mnemonic phrase. 1626^12 ~= 12^128

Re:Stop forcing arbitrary password rules by mrb on Saturday October 24, 2015 @05:27AM (#10443007)
It calculates 18 quintillion years because howsecureismypassword.net is simplistic and doesn't realize english words are being used. It categorizes each character into some categories (see https://howsecureismypassword.net/assets/js/app.min.js):

  // Standard ASCII Characters
  add('ASCII Lowercase', /[a-z]/, 26);
  add('ASCII Uppercase', /[A-Z]/, 26);
  add('ASCII Numbers', /\d/, 10);
  add('ASCII Top Row Symbols', /[!@£#\$%\^&\*\(\)\-_=\+]/, 15);
  add('ASCII Other Symbols', /[\?\/\.>\,<`~\\|"';:\]\}\[\{\s]/, 19);
  [...]
It sees the password is 22 characters long, and contains a-z chars (lowercase) and a space char (other symbols) so it estimates each char is drawn from a set of 26+19 = 45 letters. And it assumes the default bruteforcing speed is 4 billion passwords per second. So:

  45**22/4e9/3600/24/365.25 = ~18 quintillion years.
Re:Stop forcing arbitrary password rules by mrob on Saturday October 24, 2015 @06:38AM (#10443151)
It's less than that because the words were clearly not picked randomly. "Chili dog" is an English phrase, and "monkey nutso" is a transformation of "monkey nut", also an English phrase.
Re:Stop forcing arbitrary password rules by petercooper on Saturday October 24, 2015 @05:07AM (#10442970)
it's approximately 250000^4

If the attacker knows you've used four dictionary words in a row. Now you need to multiply the number by the odds of that..

Re:Stop forcing arbitrary password rules by forgotpwtomain on Saturday October 24, 2015 @05:09AM (#10442974)
It's not quite like that - even if you don't try the more readily accessible combinations before the longer ones, but simply split your computational effort on each one in proportion (you'll find all of the 4 word ones have been tried when only 1/250000 of the 5 word ones have).

Not to mention that "chili dog monkey" are not exactly rare words and even a 10k word english dictionary would contain those.

Re:Stop forcing arbitrary password rules by paulmd on Saturday October 24, 2015 @06:30AM (#10443132)
And the entropy of the password 0b0 is only a single bit - if the attacker knows you've used a single-bit password. Hashed into the SHA-256 space that's only a 1:2^256 chance of someone colliding with it. Still, is that a password you'd set?

What does that have to do with the output of the password in terms of brute-force guessing? Aren't you kind of assuming that an opponent won't try a broad dictionary attack? Equal distribution of hash outputs fundamentally assumes equivalent distributions of hash inputs, and that's not true for the distributions of common passwords.

Again - everyone knows the passphrase patterns everyone uses, everyone knows the password transformations everyone follows (eg l33t) and overall those patterns are significantly weak against attack because of this public knowledge. By those algorithm, with knowledge of salts/etc those passwords are very weak.

Should you use a song, or a slight modification, or a l33t transformation? Certainly not - if the input space isn't uniformly distributed across the input space, the probability of hitting pay dirt definitely isn't uniformly distributed across the output space.

Even the class of "valid transformations of sensical English sentences" is not an equal distribution because of the above. If you can compress a language you can attack it, because by the assumption of compression the data is not at its minimum entropy. Maybe not feasibly if you're lucky - but don't bet on it just because Webster's is big.

Re:Stop forcing arbitrary password rules by hueving on Saturday October 24, 2015 @07:41AM (#10443285)
What are you going on about? Your giant post did nothing to refute the point that an attacker doesn't know you are using 1 word vs 4 words vs 12.

Also, you seem to imply that there is a distinguishable difference in sha1 outputs of good random inputs and English word inputs, which violates a security property of cryptographic hashes. So there is a lot of fame to be had if you can prove that.

Re:Stop forcing arbitrary password rules by TomGullen on Saturday October 24, 2015 @08:28AM (#10443392)
Just cross reference with people who've posted that XKCD comic
Re:Stop forcing arbitrary password rules by ryan-c on Saturday October 24, 2015 @11:36AM (#10443885)
250,000^4 is obscenely generous. A typical person's vocabulary is maybe a tenth that, and people will be biased towards common words.
Re:Stop forcing arbitrary password rules by nsmalch on Saturday October 24, 2015 @05:15AM (#10442984)
XKCD's diceware argument fails under certain conditions. Computationally very hard to crack, but when plucked from actual phrases that have been uttered; weak.

So to give an example, any natural language phrase like:

"I took a walk in a park" is easier to crack.

I am certain there is somebody coding an infinite-monkey-type bruter to crack diceware as we speak:

https://en.wikipedia.org/wiki/Infinite_monkey_theorem

Re:Stop forcing arbitrary password rules by aruggirello on Saturday October 24, 2015 @06:34AM (#10443139)
Diceware proper is not 'plucked from actual phrases that have been uttered'. It's a random sequence obtained by throwing a dice a number of times (hence the name). This means you can't lookup your e-book collection for an exact phrase to use (eg. a famous quote).

Moreover, diceware can be set up with any dictionary, and nobody stops you from computing your own dictionary. If you do that, good luck to the bruter attempting to break your passphrase!

BTW there is no limit on the number of terms in your diceware passphrase, so if/when brute force makes 5-term phrases too weak, users may just add one or two more terms.

Re:Stop forcing arbitrary password rules by nsmalch on Saturday October 24, 2015 @06:53AM (#10443179)
Yeah what I meant is that sometimes the phrase appears like natural language, and was probably uttered once, if not on a stray ebook than somebody once said it. Of course then we have have the question of whether history starts the moment it is electronically recorded.

If NLG upsets you, you can always settle for a Markov chain and some atmospheric noise to seed the random values

Re:Stop forcing arbitrary password rules by DanBC on Saturday October 24, 2015 @06:21AM (#10443118)
I'm not sure I understand how an infinite monkey attack would work against diceware.

Let's assume a word list of 7776 words. All words are lower case alpha. The attacker has pur wordlist. And the attacker knows there are seven words in the passphrase.

That's still 7776^7.

Even if we prune the wordlist ("I'm not using 'zerg' in my phrase", "I rolled 11111, that's not random so I'll roll again") it's still not an attackable space.

Re:Stop forcing arbitrary password rules by nsmalch on Saturday October 24, 2015 @07:13AM (#10443216)
As a rule of thumb, I would go after natural language phrases first, because it is impossible to tell if the phrase was machine-generated. It's nearly impossible to arrange dots randomly on a page with a pencil because there is always some structure or engrained rigidity in human guesswork. There is also the possibility that the dots were done by 'inception', and certain biases were programmed in via subliminal messaging. Don't trust humans to do a machine's tasks.
Re:Stop forcing arbitrary password rules by DanBC on Saturday October 24, 2015 @08:47AM (#10443427)
Humans use dice to generate randomness. They throw 5 dice, to get a five digit number. They look up that number on a list to get a word. They repeat this process until they have a 7 word phrase.

So, there are weaknesses if humans roll the 5 dice and get 1, 1, 1, 1, 1 and then say "That's not random, I'll roll again"[1] or they roll a number, look it up and say "I'll never remember 'zerg', I'll roll again".

Re:Stop forcing arbitrary password rules by JoeAltmaier on Saturday October 24, 2015 @09:15AM (#10443497)
Rolling again, is no weakness at all. The next roll is also random and exactly as unguessable as the first. If the game was done 'without replacement' then the field would be reduced, but it isn't, and the field is unimaginably huge anyway. There is no effect whatsoever by 'rolling again' until you are happy with the result.

My buddy Tom always generates UUIDs by hitting the button several times. It gives him pleasure to 'waste' all those random numbers.

Re:Stop forcing arbitrary password rules by DanBC on Saturday October 24, 2015 @09:22AM (#10443509)
With diceware there's a list of 7776 words.

When someone rolls 1,1,1,1,1 and rejects that word they've cut down the word list to 7775 words. That's tiny, but it is a change.

Re:Stop forcing arbitrary password rules by JoeAltmaier on Saturday October 24, 2015 @09:32AM (#10443536)
Right, for word choice it is significant. I was thinking, rejecting the whole password pattern.
Re:Stop forcing arbitrary password rules by just_curioussss on Saturday October 24, 2015 @11:48AM (#10443920)
By rejecting a certain pattern you weakening the whole password scheme. It is no longer random, it is human chosen.

An attacker can under certain circumstances exploit this behavior. For example, if they notice you are picking shorter words or words that consist of certain characters, they will have an easier time to crack the password. Whole categories or patterns can be rejected because of that, reducing the search space.

An extreme version of your method, is picking only the patterns that relate exclusively to you, like picking your favorite music or hobbies. Then the whole scheme becomes useless.

Re:Stop forcing arbitrary password rules by JoeAltmaier on Monday October 26, 2015 @08:54AM (#10451048)
Curious notion. So, if a guy got that "human chosen" pattern randomly, they got rooked? He has a very breakable password, while the rest of us got good ones? Sounds like the whole algorithm is busted.
Re:Stop forcing arbitrary password rules by pmoriarty on Saturday October 24, 2015 @12:00PM (#10443960)
Randomness is not a property of the procedure used to generate a given set of numbers, but is rather a potential property of a set of numbers itself.