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How crackers ransack passwords like “qeadzcwrsfxv1331”

arstechnica.com

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Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#71

Post by chongli »

nknighthb wrote: post #63
chongli wrote: post #35

Earlier quoted context omitted.

I didn't say anything about reliability or single points of failure. I merely pointed out that it was possible to separate the salt from the hashes and gain security that way. Whether this is practical or not depends on how important security is to you. And yes, it would not be possible to dump the contents of the devices.

The proposal is fundamentally impractical, and thus not a "security gain" in any meaningful sense. It's the equivalent of preventing cipher algorithm breaks by using nothing but one-time pads. It's also theoretically impure in any case, as you've done nothing but add an additional peripheral to the computer. You're seeking obfuscation, not real cryptographic integrity.

>It's also theoretically impure in any case, as you've done nothing but add an additional peripheral to the computer. You're seeking obfuscation, not real cryptographic integrity.

It's not obfuscation. The peripheral has a far smaller attack surface than a server. This is real security, even if it comes at a cost of reliability (though one can envision ways of fixing this, too).

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#72

Post by nknighthb »

chongli wrote: post #71
nknighthb wrote: post #63

Earlier quoted context omitted.

The proposal is fundamentally impractical, and thus not a "security gain" in any meaningful sense. It's the equivalent of preventing cipher algorithm breaks by using nothing but one-time pads. It's also theoretically impure in any case, as you've done nothing but add an additional peripheral to the computer. You're seeking obfuscation, not real cryptographic integrity.

>It's also theoretically impure in any case, as you've done nothing but add an additional peripheral to the computer. You're seeking obfuscation, not real cryptographic integrity. It's not obfuscation. The peripheral has a far smaller attack surface than a server. This is real security, even if it comes at a cost of reliability (though one can envision ways of fixing this, too).

It's operational/system security. That's not the same thing as cryptographic security.

Stop trying to patch a hole that isn't there. Salt is not secret data. If you want to protect the hash with secret data, take A1kmm's advice and use the smart card to encrypt it. But don't call that a salt, because it fundamentally is not one.

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#73

Post by maxerickson »

davedx wrote: post #41
vinhboy wrote: post #9

I think my favorite part of this is learning that after I finish with my bitcoin mining rig, I can use it to crack passwords. Awesome...

If it's a specialised rig then it'll only be good for MD5 I think. Most sensible websites don't use MD5 anymore.

The work function in bitcoin is based on SHA-256.

But vinhboy is almost certainly talking about some computers with some GPUs in them.

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#74

Post by gradstudent »

Corrado wrote: post #53

My big takeaway from this article is that passwords, in almost any form, are a bad way to secure your information. The only acceptable way to use a password nowadays is to use a password manager to build huge passwords that a human could never remember or type in reliably. Even then, as machines get faster and crackers get smarter, these behemoth passwords will fall. I've been using 2-factor authentication (Google Au…

The "exponential wall" means the longer your password is the less likely it is to fall. A 10 letter password is in a 26^10 keyspace. Add one more letter and it takes 10 times longer to crack -- assuming of course your password is not part of some of some combination of short common dictionary words.

What I find really interesting is that the same kind of attack vector (combinations of common words) is being used as the basis for some really sophisticated search techniques in Artificial Intelligence. I remember reading an abstract a few years ago from a student of Rich Korf @ UCLA. In it the authors use this kind of approach to attack the 24-Sliding-Tile Puzzle.

Here's a link; it's pretty cool! http://www.aaai.org/ocs/index.php/AAAI/AAAI11/paper/view/349...

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#75

Post by rdl »

nknighthb wrote: post #63
chongli wrote: post #35

Earlier quoted context omitted.

I didn't say anything about reliability or single points of failure. I merely pointed out that it was possible to separate the salt from the hashes and gain security that way. Whether this is practical or not depends on how important security is to you. And yes, it would not be possible to dump the contents of the devices.

The proposal is fundamentally impractical, and thus not a "security gain" in any meaningful sense. It's the equivalent of preventing cipher algorithm breaks by using nothing but one-time pads. It's also theoretically impure in any case, as you've done nothing but add an additional peripheral to the computer. You're seeking obfuscation, not real cryptographic integrity.

No, using an HSM to store a secret is done widely (in banking, for PINs), and it's entirely possible to implement them in a way where individual device failures can be mitigated.

The only issue is cost of HSMs; they're about $20k/ea right now, since there are only two significant vendors, and they're not widely used.

If someone wanted to do "HSM for general purpose web login, to eliminate the DoS potential of scrypt, and the brute force hash db problem of anything else, and the idiocy of plaintext", the price could probably drop down to $500 or less.

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#76

Post by rdl »

gradstudent wrote: post #74
Corrado wrote: post #53

My big takeaway from this article is that passwords, in almost any form, are a bad way to secure your information. The only acceptable way to use a password nowadays is to use a password manager to build huge passwords that a human could never remember or type in reliably. Even then, as machines get faster and crackers get smarter, these behemoth passwords will fall. I've been using 2-factor authentication (Google Au…

The "exponential wall" means the longer your password is the less likely it is to fall. A 10 letter password is in a 26^10 keyspace. Add one more letter and it takes 10 times longer to crack -- assuming of course your password is not part of some of some combination of short common dictionary words. What I find really interesting is that the same kind of attack vector (combinations of common words) is being used as t…

not 10x longer, 26x longer (and that's assuming lowercase a-z only)

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#77

Post by chiph »

_b8r0 wrote: post #55
tomku wrote: post #3

Enjoyable read, but I question the bit near the end claiming that salts wouldn't help much against this kind of attack. From my understanding, per-user salting does substantially slow down this kind of attack because it forces you to calculate a different hash for each user/plaintext combination rather than hashing a suspected plaintext once and comparing the hash against the whole list. What it doesn't slow down is…

I'm in the middle of researching re-evaluating rainbow table attacks in light of Moore's law, GPUs and Crack (lookup) tables, I've also looked into countermeasures. What you're describing is partially correct. When you crack passwords (either with rainbow tables or by brute force) you generate an iterator or use a dictionary and work through this generating hashes (with rainbow tables this works via a series (or chai…

If you're targeting a single hash

I was going to mention this. If your user record has a column called "IsSuperuser", then an attacker is going to concentrate on those users, since the reward for cracking them is so much higher. Individual salts or not, with multi-GPU based brute-forcing, they won't stand long.

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#78

Post by mrgoldenbrown »

I don't understand the statement that salts get less effective after you've broken other passwords:

"But the thing about salting is this: it slows down cracking only by a multiple of the number of unique salts in a given list. That means the benefit of salting diminishes with each cracked hash."

A proper salt for user Joe's password does not have any relation to any other user's salt. Cracking Bob's password should not help you crack Joe's. Am I missing a technique that exploits one salt to attack another? Or are they assuming crappy salting methods? As in, if you have 2 bits of salt, then after the attacker has hashed your entire passwd file with those 4 salts, you might as well not have salted anything.

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#79

Post by makira »

mrgoldenbrown wrote: post #78

I don't understand the statement that salts get less effective after you've broken other passwords: "But the thing about salting is this: it slows down cracking only by a multiple of the number of unique salts in a given list. That means the benefit of salting diminishes with each cracked hash." A proper salt for user Joe's password does not have any relation to any other user's salt. Cracking Bob's password should n…

If the original list had x salts, and you crack half of the entries, then you only have x/2 salts left to check, hence cracking goes twice faster.

Re: How crackers ransack passwords like “qeadzcwrsfxv1331”

#80

Post by shawabawa3 »

mrgoldenbrown wrote: post #78

I don't understand the statement that salts get less effective after you've broken other passwords: "But the thing about salting is this: it slows down cracking only by a multiple of the number of unique salts in a given list. That means the benefit of salting diminishes with each cracked hash." A proper salt for user Joe's password does not have any relation to any other user's salt. Cracking Bob's password should n…

I think what he means is that every password you crack is one less salt you have to hash with. Once you've cracked half the passwords, there are only half as many salts you need to hash with.

However I think he's underestimating how much strength this adds, it would have delayed that 1 hour to get 62% of the passwords to probably a few thousand hours.

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