Comment by newscracker | Hacker News Reader

Comment by newscracker | Hacker News Reader

It’s good to recommend that passwords be 12 characters or longer, and the password-strength meter seems good enough. I tested it with CorrectHorseBatteryStaple (from xkcd 936) and it said the password is strong. But what I didn’t like in the suggestions in the demo strength meter site is that it keeps suggesting that the user avoid dictionary words and add one more symbols or one more digits.

> Your password is pretty good. Use it only for this account. (Why?)

> To make it even better:

> Don't use dictionary words (Correct, Battery, Staple and Horse) (Why?)

> Consider using 1 or more symbols (Why?)

> Consider using 1 or more digits

This essentially goes against the advice that passwords should be complex but also easier to remember (yes, many people still don’t use password managers) and also the advice not to force users to add symbols or digits.

I tried a few other different passwords and pass phrases with digits and symbols, but I saw a subtle coercion in the suggestions that would make a lay user doubt the password-strength meter and create extremely long and complex passwords (no pass phrases, since dictionary words and even terms in Wikipedia are flagged). It encourages you to add more digits and symbols even when you’ve already used a few.

In short, the password-strength meter seems fine, but the suggestions are not great.

It withdraws those suggestions if you make it long enough. For example, "horsecardoghousemailglassplate" has no improvement suggestions, but until that final "plate" is added it says not to use words, and to add symbols and upper case.

Another example is "195884873718293401958657". Until that last 7 is added, it suggests avoiding dates (1958), repeating sections (1958), and having very common passwords (718293) is part of your password, but when that last 7 is added the suggestions go away.

Doesn’t it just give up on giving you suggestions after a certain size?

In my first example the suggestions stop at character 30. In my second example the suggestions stop at character 24. For a password that is all ‘a’s they stop at character 68.

I’d guess it stops making suggestions when it reaches a certain estimated strength. The suggestions are ways to reach that strength efficiently.

12 characters is only 72 bits of entropy, and that’s assuming you’re using randomly generated passwords with an equal probability distribution of the entire set of printable base64 characters.

That’s nowhere near enough entropy for a proper password.

Just use the damn password manager already.

I just changed my PayPal password today; they restrict the length of a password to between 8-20 characters. Why the upper limit? Once you're at 20, you're likely using a password manager, so another 20 wouldn't hurt.

> 12 characters is only 72 bits of entropy ... That’s nowhere near enough entropy for a proper password.

What do you base that on?

If you assume the password is stored using current best practices (ie, you use a key definition function like PBKDF2 or even better scrypt), it's tons. You can't assume a website will be using anything reasonable - but anything I manually enter this 12 character password into, like a password manager a modern auth service, or ssh it is reasonable.

Proof: assume you use a KDF that makes a check of a single password take at least 1ms on modern reasonable machine, 72 bits means it will take 149,642,763,799 (= 2^72 / 3600.0 / 1000.0 / 24 / 365.35) years to break. Sure you can parallelise it, so lets throw a billion of these "reasonable machines" at it. That reduces it to 149 years. I'll be well and truly six foot under before they crack it, which meets my definition of tons.

But it's better to look at it from the point of view of the worth of the information they get versus expense. Let's say for argument's sake my entire net worth is $100M. Lets also also say a "reasonable machine" worth $10. And finally assume the value of that $100M shrinks over time, so after 20 years it's worth almost nothing. Continue assuming we use a KDF to ensure doing one guess takes 1 second, and you end up with needing 62 bits of entropy - or 11 characters.

I tried the demo, and could not come up with a 12-character password that got a good score and was not just impossible-to-remember random jibberish.

I'll stick with generated pseudo-random gibberish and a password manager.

`openssl rand n | base64` is my go to

You can use openssl rand -base64 n to save a pipe.

The average person's working vocabulary is 20,000 words, do you expect a layman to be able to produce a perfectly random combination out of the paltry 20000⁴ possible sequences. Will they reach into the outer edges of their vocabulary to use obscure words? Surely it would be biased towards common words, making even bcrypt pointless.

With respect, maybe your vocabulary is 20,000 words, but I submit that the average English-only speaker is more like about 10,000 words.

This is a case where I choose to believe xkcd unless and until you can provide convincing evidence otherwise.

The total possible permutations of characters in just an alphanumeric 12 digit random password is 36¹², which is around 400 times larger than the number of permutations possible with 4 words picked out of a pool of 10,000 or 10000⁴.

This might seem reasonable, however, this is only a false economy as people tend to gravitate towards common words that evoke simple concepts, which drastically reduces the search space.

A dictionary attack isn't anything novel and the proliferation of this technique would only make life easier for the baddies.

You could argue that passphrases aren't even competing with randomly generated passwords but rather with the naive passwords that people come up with that has simple character substitution for special characters.

However, this is the same reason why it should only be confined to use in places where a yubikey for active directory windows login or a password manager wouldn't be practical.

If you're going to use a tool to generate your passphrase, why not use a tool to store it and retrieve it at will, while also protecting yourself from shoulder surfing?

If they're "reaching into the edges of their vocabulary" they're doing it wrong anyway. People are terrible random number generators. Don't do that. Use an actual random number generator to select a sequence of words from a list.

> Use an actual random number generator to select a sequence of words from a list

I wrote a program to do this for me which I myself use, and anyone else is free to download and use it (open source, ISC license) :D

It supports a few different options, including one that will tell you what the passphrase entropy would be.

https://github.com/ctsrc/Pgen

This is something where there is value in having a generator to do the password creation. That way the use only needs to remember the phrase rather than also come up with it.

If using a password manager then memorization is less useful while fully random passwords are considerably stringer.

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