4 ms·

The problem with all of this is that security specialists (of which I am one, guilty as charged) have historically campaigned for more complex passwords. This w

by iuguy 14y ago

The problem with all of this is that security specialists (of which I am one, guilty as charged) have historically campaigned for more complex passwords. This worked well for conventional (non-clustered, non-accelerated) password cracking mechanisms. Sadly, this starts to fall apart with accelerated and/or distributed cracking. On average I crack a few hundred passwords a week, and more often than not organisations have what I call seed words (e.g. the password reset word or common words used throughout the organisation) and the majority of passwords are variants of them. My own ability to crack passwords for most algorithms (within a reasonable timeframe) tends to cap at dictionary words with number and letter substitution and somewhere around the 8-10 character mark. Using a phrase means that as an attacker you have to account for other people using more complex but shorter passwords. I'd still suggest getting capitalisation, punctuation or at least a number in your phrase but the bulk of the keyspace comes from the length rather than complexity plus the fact that the people carrying out these attacks are normally cracking more than one password at a time. For a few years now (since around the time of Oeschlin's paper[1]) I've been advising customers to use longer passwords made of phrases and things they can remember for passwords they regularly use[2] and randomly generated passwords of some length stored in a password safe[3] for things they might forget. The goal of this advice is to make it harder for people to crack passwords and to reduce the volume of passwords people have to remember. [1] - http://lasec.epfl.ch/pub/lasec/doc/oech03.pdf http://lasec.epfl.ch/pub/lasec/doc/oech03.pdf [2] - http://xkcd.com/936/ http://xkcd.com/936/ [3] - http://keepass.info/ http://keepass.info/ - one of many options available

sspiff 14y ago
Since reading that xkcd, I use phrases as passwords, using a simple Ruby script to generate them: w = File.readlines('/usr/share/dict/words').map { |w| w.chomp }.reject { |w| w !~ /^[A-Za-z]+$/ }; 3.times { print w[rand * w.size] }; puts I generally get an easy to remember password after about 3 tries. The biggest issue I have with this is typing in passwords on mobile devices.
- _ikke_ 14y ago
  Aren't phrases easier to type on mobile devices than letter / number combinations? I always find it annoying to have to switch to different keyboard modes (text / numbers), or having to hold the letter / number key for a few seconds.
  - sspiff 14y ago
    Sure, the simple characters make it a bit easier, but the phrases tend to be much longer. The error rate on a touchscreen keyboard is high enough to really become a problem at 20+ characters when you only see the last typed character (no password review).
    - Karunamon 14y ago
      Using dictionary words makes it easy for more modern predictive keyboards to keep up, though. Taking the XKCD canonical example, "correct horse battery staple", it's a reasonably secure and lengthy password and includes special characters. It could also be keyed in via something like Swype or SlideIT in almost as fast as it could be keyed in on a computer keyboard.
      - sspiff 14y ago
        Perhaps, depending on the user. Doesn't work well for me though.
  - rootbear 14y ago
    Yeah, the iPhone keyboard is what finally got me to stop using r2d2 or c3p0 as a part of my password. And the fact that they are probably in the cracking dictionaries.
- trebor 14y ago
  A slight refactoring for Ruby 1.9.3 users, uses Array#sample to grab 3 random words, etc. ruby -e 'w = File.readlines("/usr/share/dict/words").map { |w| w.chomp }.reject { |w| w !~ /^[A-Za-z]+$/ }; puts w.sample(3).join(" ").downcase'
- CodesInChaos 14y ago
  Is `rand` a secure random number in ruby? In many programming languages/implementations the default PRNG is only seeded with the current time, which leads to quite low entropy.
ZoFreX 14y ago
It's worth pointing out that length is not important, only entropy is important. If you create a really long phrase by forming a sentence from very common English words, the entropy is actually really low, and if everyone started doing this you can bet your boots the password crackers would catch up. However you create your password you should take a stab at calculating the entropy (and incidentally a 10 character truly random password with alphanumeric+specials will be very hard to crack - it's the fact that the passwords are mutations of a seed word that makes them weak, and not their short length)
- rmc 14y ago
  It's worth pointing out that length is not important, only entropy is important Exactly. This is a weak password: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaa" or "qwertyuiopqwertyuiop"
- vonuebelgarten 14y ago
  > It's worth pointing out that length is not important, only entropy is important. Entropy is important, but multi-word passwords stills being efficient since their alphabet is quite large when compared with common alpha-symbolic-numeric passwords. For example, a completely random password with 12 digits and upper/lower case letters have (26+26+10)^12 = 3.226e21 possibilities. Quite good unless you need to memorize this thing. I use such nonsense things for password stored in my password safe. A password with four very common words (among the 1000 most common words in the user's native language, which I assume the attacker know) have 1e9 possibilities -- very bad. Relevant XKCD for explaining how bizarre is an English text with such restricted vocabulary: https://xkcd.com/1133/ https://xkcd.com/1133/ A password with five words selected among the most 4000 words of the user's native language have 1.024e+18 possibilities. Put some uncommon/random/made-up word in the mix is enough to make a direct attack on the password non-viable and force the attacker to search for more elaborated methods. Plus side: is easy to memorize.
  - codex 14y ago
    I should point out that multi-word passwords have at least one disadvantage: if you can figure out which letters were used and/or the password's length, and you know the password is multi-word, then it becomes easier to derive what the password was. So, for example, if you used a multi-word password on your ATM machine, and someone aimed an infrared camera at the machine after you left and retrieved the set of buttons that you pressed, the game would be over if your password were short--or at least much closer to being over if it were long. Alternatively, an attacker could eavesdrop on your keyboard sounds and capture the timing of the clicks, thereby inferring candidate sets of letters. Or they could examine how much oil is on each key of your keyboard, or how much each key is worn, and adjust for the stats on the English language, etc. Or, as in the ATM case, an agent could interrupt you right after you've entered your password on a false pretext ("Excuse me, I need help.") and surreptitiously take an in infrared photo of your keyboard. This is plausible in many semi-public scenarios (bank teller, etc.) I think the saving grace here is that a sufficiently long password uses most letters in the English alphabet--but it is still prone to attack if you can at least get the relative ordering of some of the letters, or you know the password's length (by listening to the number of keyboard clicks, for example).

by iuguy 14y ago

sspiff 14y ago

Since reading that xkcd, I use phrases as passwords, using a simple Ruby script to generate them: w = File.readlines('/usr/share/dict/words').map { |w| w.chomp }.reject { |w| w !~ /^[A-Za-z]+$/ }; 3.times { print w[rand * w.size] }; puts I generally get an easy to remember password after about 3 tries. The biggest issue I have with this is typing in passwords on mobile devices.

_ikke_ 14y ago
Aren't phrases easier to type on mobile devices than letter / number combinations? I always find it annoying to have to switch to different keyboard modes (text / numbers), or having to hold the letter / number key for a few seconds.
- sspiff 14y ago
  Sure, the simple characters make it a bit easier, but the phrases tend to be much longer. The error rate on a touchscreen keyboard is high enough to really become a problem at 20+ characters when you only see the last typed character (no password review).
  - Karunamon 14y ago
    Using dictionary words makes it easy for more modern predictive keyboards to keep up, though. Taking the XKCD canonical example, "correct horse battery staple", it's a reasonably secure and lengthy password and includes special characters. It could also be keyed in via something like Swype or SlideIT in almost as fast as it could be keyed in on a computer keyboard.
    - sspiff 14y ago
      Perhaps, depending on the user. Doesn't work well for me though.
- rootbear 14y ago
  Yeah, the iPhone keyboard is what finally got me to stop using r2d2 or c3p0 as a part of my password. And the fact that they are probably in the cracking dictionaries.
trebor 14y ago
A slight refactoring for Ruby 1.9.3 users, uses Array#sample to grab 3 random words, etc. ruby -e 'w = File.readlines("/usr/share/dict/words").map { |w| w.chomp }.reject { |w| w !~ /^[A-Za-z]+$/ }; puts w.sample(3).join(" ").downcase'
CodesInChaos 14y ago
Is `rand` a secure random number in ruby? In many programming languages/implementations the default PRNG is only seeded with the current time, which leads to quite low entropy.

ZoFreX 14y ago

It's worth pointing out that length is not important, only entropy is important. If you create a really long phrase by forming a sentence from very common English words, the entropy is actually really low, and if everyone started doing this you can bet your boots the password crackers would catch up. However you create your password you should take a stab at calculating the entropy (and incidentally a 10 character truly random password with alphanumeric+specials will be very hard to crack - it's the fact that the passwords are mutations of a seed word that makes them weak, and not their short length)

rmc 14y ago
It's worth pointing out that length is not important, only entropy is important Exactly. This is a weak password: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaa" or "qwertyuiopqwertyuiop"
vonuebelgarten 14y ago
> It's worth pointing out that length is not important, only entropy is important. Entropy is important, but multi-word passwords stills being efficient since their alphabet is quite large when compared with common alpha-symbolic-numeric passwords. For example, a completely random password with 12 digits and upper/lower case letters have (26+26+10)^12 = 3.226e21 possibilities. Quite good unless you need to memorize this thing. I use such nonsense things for password stored in my password safe. A password with four very common words (among the 1000 most common words in the user's native language, which I assume the attacker know) have 1e9 possibilities -- very bad. Relevant XKCD for explaining how bizarre is an English text with such restricted vocabulary: https://xkcd.com/1133/ https://xkcd.com/1133/ A password with five words selected among the most 4000 words of the user's native language have 1.024e+18 possibilities. Put some uncommon/random/made-up word in the mix is enough to make a direct attack on the password non-viable and force the attacker to search for more elaborated methods. Plus side: is easy to memorize.
- codex 14y ago
  I should point out that multi-word passwords have at least one disadvantage: if you can figure out which letters were used and/or the password's length, and you know the password is multi-word, then it becomes easier to derive what the password was. So, for example, if you used a multi-word password on your ATM machine, and someone aimed an infrared camera at the machine after you left and retrieved the set of buttons that you pressed, the game would be over if your password were short--or at least much closer to being over if it were long. Alternatively, an attacker could eavesdrop on your keyboard sounds and capture the timing of the clicks, thereby inferring candidate sets of letters. Or they could examine how much oil is on each key of your keyboard, or how much each key is worn, and adjust for the stats on the English language, etc. Or, as in the ATM case, an agent could interrupt you right after you've entered your password on a false pretext ("Excuse me, I need help.") and surreptitiously take an in infrared photo of your keyboard. This is plausible in many semi-public scenarios (bank teller, etc.) I think the saving grace here is that a sufficiently long password uses most letters in the English alphabet--but it is still prone to attack if you can at least get the relative ordering of some of the letters, or you know the password's length (by listening to the number of keyboard clicks, for example).