6 ms·

1: Change your password. RIGHT NOW. If you’re not sure how strong your password is, test sample passwords with our password checker here. Seriously? Keep in mi

by wglb 10y ago

1: Change your password. RIGHT NOW. If you’re not sure how strong your password is, test sample passwords with our password checker here. Seriously? Keep in mind that these estimates are based on some bogus entropy estimation. If a password hacking guy runs the correct dictionary past the hashes you password generates, it might be as small, well, as the first one tried. For example, run the passphrase Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn1 past the kaspersky bruteforce estimator, you get 10,000 centuries. But this is clearly false, as inicated in http://arstechnica.com/security/2013/08/thereisnofatebutwhatwemake-turbo-charged-cracking-comes-to-long-passwords/ http://arstechnica.com/security/2013/08/thereisnofatebutwhat.... They clearly "cracked" this in far less time: "in a matter of minutes".

saidajigumi 10y ago
As an aside, it can be so difficult to get this across to folks who aren't in the infosec headspace. I've seen even technical, computer science types absolutely not get that their ad-hoc memorable password "but no one would EVER guess that!" schemes are probably much more vulnerable than they estimate. Nevermind, even, true computing laypersons.
- ben_jones 10y ago
  We have to rotate our password advice to family and friends every couple years or so. It used to be "use a random combination of memorable words with a number thrown in" a la "reddogbarkhard7". Now I feel like right after guessing the 10k most common passwords a hacker would immediately brute word combinations with a single integer ending.
  - yoha 10y ago
    The worst bias is letting the users choose their passwords. They should use a generator such as [1]. The reason is that the "entropy" is not a characteristic of a password but of the way it is generated. Computers are much better at entropy than humans. [1] http://passwordcreator.org/ http://passwordcreator.org/
    - zamalek 10y ago
      Or, better yet, a password manager. If you aren't using one yet, now is a great opportunity.
      - yoha 10y ago
        I agree that password managers are great. They let you use completely different passwords for each service, efficiently mitigating any compromise. Also, they tend to encourage you to use actually random passwords (using a generator). However, most users will not bother, and getting them to use at least decent passwords would be a great step forward. Additionally, you still need a master password for your password manager.
        ben_jones 10y ago
        Also you can't really rely on a free password manager (which is what users will generally select) to be a long-time solution. Either because they go out of business, change their monetization model, get hacked, whatever. It's one of those things that sounds good, but in reality is unable to gain critical mass for human reasons.
    - Ntrails 10y ago
      Work sent around a stupid cardboard stand which was supposed to tell us all about being excellent at our work, and the checking processes required before sending anything to clients etc etc. We were changing domains at the same time, so my new password root is now based on the first three characters of the first 3 lines of the thing, which included some punctuation, then the standard numeral to increment every 90 days. My password was in plain sight for a couple months before I got around to binning it, which actually makes life a lot easier. Especially when you're not using it often enough for it to be muscle memory - which is the problem my parents face.
      - yoha 10y ago
        However, such an approach corresponds to a few dozens bits of entropy at best (some for the approach, some for the length of text used, and a few for the numeral depending on whence it comes). As stated by zamalek, the trick to not memorizing many passwords is to use a password manager.
- ashitlerferad 10y ago
  The only sane schemes are ones that choose passphrases solely based on entropy. So, Diceware or other random generation systems.
- joepie91_ 10y ago
  I've found that it helps to, rather than going directly into the mathematics of it all, explain to somebody that their password is going to be cracked by a computer rather than a human, and computers 'think differently'. Thus, you need to make things that seem complex to computers, not things that seem complex to humans. The same applies verbatim for people trying to roll their own 'clever' encryption schemes.
fnordsensei 10y ago
So, being one of the people who hovers around laymanship when it comes to these questions, how hard is it to crack a randomly generated 25 character string with 5 digits and 5 symbols? This is typically what I would use for a website.
- chronial 10y ago
  How do you randomly generate these passwords?
  - iimpact 10y ago
    password managers
    - sbierwagen 10y ago
      Tinfoil hat time: if your password manager uses a bad generation scheme or backdoored RNG like Dual EC, then its passwords might be much easier to crack than they would appear. https://en.wikipedia.org/wiki/Dual_EC_DRBG https://en.wikipedia.org/wiki/Dual_EC_DRBG
      - dwightgunning 10y ago
        This is always my concern. At some point the password managers become an interesting attack vector. Why can't people just be nice.
      - bigiain 10y ago
        I know you covered yourself with the tinfoil disclaimer, but Ima take you seriously here for a thought experiment... I wonder if that's actually a risk? At least for people not being individually targeted? A random Elbonian hacker who gets a dump of 117 million password hashes has (at least) three approaches she can take to make use of it - she can run oclHashcat or JtR using a good wordlist (say, Hashkiller or phpbb) and a reasonable ruleset to tweak them, which'll fairly quickly reveal common, reused, or guessable passwords in hours/days/weeks - or she can set it to enumerate through an entire $howeverymany bit password space, which is guaranteed to find all the passwords but not before the heat death of the universe... Or she could try only the selections out of that random keyspace that a flawed version of FooPasswordSafe is capable of generating. I'm not sure how long the last approach would take, but it'd have to be both a pretty flawed PRNG and a very widely used password safe for it to come anywhere near as useful as approach 1. (If she's only cracking the hash for the sbeirwagen@gmail.com record, things are somewhat different to if she's just trying to find _any_ "useable" passwords out of 117 million... And if she _knows_ sbeirwagen uses DudPasswordSafe.exe, it's likely she knows better ways of attempting to acquire your password than hoping to crack it from publicly released credential dumps...)
OhHeyItsE 10y ago
Aren't cracks of this nature thwarted by salting?
- ryanlol 10y ago
  No. Salting mostly prevents rainbow tables from being very useful, but rainbow tables are questionably useful anyway with modern hardware. (Obviously depending on the type of the hash)
  - OhHeyItsE 10y ago
    Yeah but isn't this method just a giant rainbow table whose source is crawlable web content? >It would have been impossible to use a brute-force attack or even a combined dictionary to crack a phrase of that length. But because the phrase was contained in this Wikipedia article, it wound up in a word list that allowed Chrysannthou to crack the phrase in a matter of minutes.
    - wglb 10y ago
      No, a rainbow table is just a method to pre-compute hashes. Given that you can, for $500 buy a graphics card that can compute seven hundred million hashes a second, precomputation is not really of any value. The attack described is to find potential passwords on the web or somewhere, compute the hash, see if it matches. Rainbow tables aren't any part of this process.
    - d_k_f 10y ago
      This most likely depends on the way you look at it (or rather how exactly he did it): did he take the word list, generate hashes from it and then check them against leaked hashes? Rainbow table. If he took the word list to run login attempts against a server (or a local endpoint checking the leaked database) it's more of a dictionary attack. Same result, different ways to get there. If you're able to run your cracker locally against a leaked db, it probably doesn't really matter.
scoot 10y ago
>> test sample passwords with our password checker > Seriously? Sample passwords, not your actual passwords. If you follow that link, they reinforce that with: "Never enter your real password".
- wglb 10y ago
  Yes, that is the actual instructions that they give. Imagine a relative of yours who is much less computer savvy than you are. What are the chances that the actually enter their real password? And what value is this check, actually, on a fake password. "Your fake password will take xxx centuries to crack". So how does the non-tech savvy person, who might have a struggle coming up with a real, useful password, then enter one that is similar but not exact and expect a measured response? So even if they collect "simulated" passwords, password cracking is less about entropy and more about generating dictionaries based on patterns that users are likely to use. There isn't any value in such a site, and I claim it is less than useful.
- dclowd9901 10y ago
  Ok... 10,000^4 * 10 = 100,000,000,000,000,000 @1,000,000,000,000 passes per second (nsa level bruting) = 27 hours to break one single password. There's far more low hanging fruit in an encrypted list of passwords than to bother with random common word combos. Unless you're a specific target, it's not lucrative to a hacker to use brute forcing to get through the last 10 or 20% of users with good passwords.
deleted 10y ago
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by wglb 10y ago

saidajigumi 10y ago

As an aside, it can be so difficult to get this across to folks who aren't in the infosec headspace. I've seen even technical, computer science types absolutely not get that their ad-hoc memorable password "but no one would EVER guess that!" schemes are probably much more vulnerable than they estimate. Nevermind, even, true computing laypersons.

ben_jones 10y ago
We have to rotate our password advice to family and friends every couple years or so. It used to be "use a random combination of memorable words with a number thrown in" a la "reddogbarkhard7". Now I feel like right after guessing the 10k most common passwords a hacker would immediately brute word combinations with a single integer ending.
- yoha 10y ago
  The worst bias is letting the users choose their passwords. They should use a generator such as [1]. The reason is that the "entropy" is not a characteristic of a password but of the way it is generated. Computers are much better at entropy than humans. [1] http://passwordcreator.org/ http://passwordcreator.org/
  - zamalek 10y ago
    Or, better yet, a password manager. If you aren't using one yet, now is a great opportunity.
    - yoha 10y ago
      I agree that password managers are great. They let you use completely different passwords for each service, efficiently mitigating any compromise. Also, they tend to encourage you to use actually random passwords (using a generator). However, most users will not bother, and getting them to use at least decent passwords would be a great step forward. Additionally, you still need a master password for your password manager.
      - ben_jones 10y ago
        Also you can't really rely on a free password manager (which is what users will generally select) to be a long-time solution. Either because they go out of business, change their monetization model, get hacked, whatever. It's one of those things that sounds good, but in reality is unable to gain critical mass for human reasons.
  - Ntrails 10y ago
    Work sent around a stupid cardboard stand which was supposed to tell us all about being excellent at our work, and the checking processes required before sending anything to clients etc etc. We were changing domains at the same time, so my new password root is now based on the first three characters of the first 3 lines of the thing, which included some punctuation, then the standard numeral to increment every 90 days. My password was in plain sight for a couple months before I got around to binning it, which actually makes life a lot easier. Especially when you're not using it often enough for it to be muscle memory - which is the problem my parents face.
    - yoha 10y ago
      However, such an approach corresponds to a few dozens bits of entropy at best (some for the approach, some for the length of text used, and a few for the numeral depending on whence it comes). As stated by zamalek, the trick to not memorizing many passwords is to use a password manager.
ashitlerferad 10y ago
The only sane schemes are ones that choose passphrases solely based on entropy. So, Diceware or other random generation systems.
joepie91_ 10y ago
I've found that it helps to, rather than going directly into the mathematics of it all, explain to somebody that their password is going to be cracked by a computer rather than a human, and computers 'think differently'. Thus, you need to make things that seem complex to computers, not things that seem complex to humans. The same applies verbatim for people trying to roll their own 'clever' encryption schemes.

fnordsensei 10y ago

So, being one of the people who hovers around laymanship when it comes to these questions, how hard is it to crack a randomly generated 25 character string with 5 digits and 5 symbols? This is typically what I would use for a website.

chronial 10y ago
How do you randomly generate these passwords?
- iimpact 10y ago
  password managers
  - sbierwagen 10y ago
    Tinfoil hat time: if your password manager uses a bad generation scheme or backdoored RNG like Dual EC, then its passwords might be much easier to crack than they would appear. https://en.wikipedia.org/wiki/Dual_EC_DRBG https://en.wikipedia.org/wiki/Dual_EC_DRBG
    - dwightgunning 10y ago
      This is always my concern. At some point the password managers become an interesting attack vector. Why can't people just be nice.
    - bigiain 10y ago
      I know you covered yourself with the tinfoil disclaimer, but Ima take you seriously here for a thought experiment... I wonder if that's actually a risk? At least for people not being individually targeted? A random Elbonian hacker who gets a dump of 117 million password hashes has (at least) three approaches she can take to make use of it - she can run oclHashcat or JtR using a good wordlist (say, Hashkiller or phpbb) and a reasonable ruleset to tweak them, which'll fairly quickly reveal common, reused, or guessable passwords in hours/days/weeks - or she can set it to enumerate through an entire $howeverymany bit password space, which is guaranteed to find all the passwords but not before the heat death of the universe... Or she could try only the selections out of that random keyspace that a flawed version of FooPasswordSafe is capable of generating. I'm not sure how long the last approach would take, but it'd have to be both a pretty flawed PRNG and a very widely used password safe for it to come anywhere near as useful as approach 1. (If she's only cracking the hash for the sbeirwagen@gmail.com record, things are somewhat different to if she's just trying to find _any_ "useable" passwords out of 117 million... And if she _knows_ sbeirwagen uses DudPasswordSafe.exe, it's likely she knows better ways of attempting to acquire your password than hoping to crack it from publicly released credential dumps...)

OhHeyItsE 10y ago

Aren't cracks of this nature thwarted by salting?

ryanlol 10y ago
No. Salting mostly prevents rainbow tables from being very useful, but rainbow tables are questionably useful anyway with modern hardware. (Obviously depending on the type of the hash)
- OhHeyItsE 10y ago
  Yeah but isn't this method just a giant rainbow table whose source is crawlable web content? >It would have been impossible to use a brute-force attack or even a combined dictionary to crack a phrase of that length. But because the phrase was contained in this Wikipedia article, it wound up in a word list that allowed Chrysannthou to crack the phrase in a matter of minutes.
  - wglb 10y ago
    No, a rainbow table is just a method to pre-compute hashes. Given that you can, for $500 buy a graphics card that can compute seven hundred million hashes a second, precomputation is not really of any value. The attack described is to find potential passwords on the web or somewhere, compute the hash, see if it matches. Rainbow tables aren't any part of this process.
  - d_k_f 10y ago
    This most likely depends on the way you look at it (or rather how exactly he did it): did he take the word list, generate hashes from it and then check them against leaked hashes? Rainbow table. If he took the word list to run login attempts against a server (or a local endpoint checking the leaked database) it's more of a dictionary attack. Same result, different ways to get there. If you're able to run your cracker locally against a leaked db, it probably doesn't really matter.

scoot 10y ago

>> test sample passwords with our password checker > Seriously? Sample passwords, not your actual passwords. If you follow that link, they reinforce that with: "Never enter your real password".

wglb 10y ago
Yes, that is the actual instructions that they give. Imagine a relative of yours who is much less computer savvy than you are. What are the chances that the actually enter their real password? And what value is this check, actually, on a fake password. "Your fake password will take xxx centuries to crack". So how does the non-tech savvy person, who might have a struggle coming up with a real, useful password, then enter one that is similar but not exact and expect a measured response? So even if they collect "simulated" passwords, password cracking is less about entropy and more about generating dictionaries based on patterns that users are likely to use. There isn't any value in such a site, and I claim it is less than useful.
dclowd9901 10y ago
Ok... 10,000^4 * 10 = 100,000,000,000,000,000 @1,000,000,000,000 passes per second (nsa level bruting) = 27 hours to break one single password. There's far more low hanging fruit in an encrypted list of passwords than to bother with random common word combos. Unless you're a specific target, it's not lucrative to a hacker to use brute forcing to get through the last 10 or 20% of users with good passwords.

deleted 10y ago

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