How long does it actually take in practice to break something like this? I would love it if someone could prove it to me.
I just googled it and found https://hashtoolkit.com/decrypt-sha1-hash/b85ffa7dae2cbed04e... along with other results.
Can I try again? Sha1 e7b7cdf949007abe7e8a190ba8eae56c60018c1f
Took me 6 minutes to try all 1.4 trillion passwords. So either you have a strong password or I messed something up. What is it?
In theory if your password was weak enough to be on this list it would take on average 3 minutes to break it on a GTX 1080.
Anything under 9 characters I can brute force in minutes. 9 character passwords would take me 9 hours.
Obviously if someone has a nest of the latest GPUs then they could go a lot faster.
But yes if your password is uwv&6qu_brusb618_$@618jg then it doesn’t really matter how you hash it.
No, it doesn't. You could reuse uwv&6qu_brusb618_$@618jg everywhere and it wouldn't get cracked. If the plaintext password leaked, then you'd be in more trouble.
What matters is whether your password is easy to guess, not whether you've reused it. If you have all unique passwords, they can still all be trivial to crack.
Sha1 is not a very secure/expensive hashing algorithm and thus does make it significantly cheaper to break even with a unique salt.
Your idea of what a rainbow table is appears to be unrelated to what a rainbow table actually is. A rainbow table is prepared in advance, not generated in the process of cracking an individual password.
Ok, so how long does it take to break the hash I've provided if it's not very secure?
So the answer is "It's too expensive to figure out in practice, unless you're being explicitly targetted by someone with nation state level credentials?", i.e. it's pretty much fine?
> Using a more appropriate hashing algorithm with a sufficient cost factor can massively increase the amount of compute needed.
But by the sounds of it, SHA1 is more than enough (given that nobody here is willing to brute force the hash I shared above?)
> Preventing the re-use of that computational effort on additional users is why unique salts are important.
The person who "cracked" my first hash found it in a list of passwords which was actually gotten from a plain text dump 15 years ago. That wasn't found by reversing a hash, so the compute wasn't reused. You are right that once it's cracked, it's cracked and that's that, but if your password _isn't_ cracked it's moot whether it's hashed with SHA1 or something more secure, as per above?
SHA1 is "more than enough" for this specific interaction in which you chose a complex password and/or your only opponents are unmotivated/non-incentivized HN commenters that don't have a password cracker at their immediate disposal. That doesn't mean anything outside of this context.
If your opponent was a motivated hacker with dedicated password cracking machines (which do not require anything even close to a nation-state budget, btw), your SHA1 hash would be much more likely to be cracked. If you were a specific target of a hacker group, such as an employee of a company that is being targeted by an attack or someone known to have a BTC wallet with $10 million in it, your SHA1 hash would be much more likely to be cracked. If your password was a relatively simple phrase like "dog$aregreat2019", like the vast majority of user passwords are, it would almost certainly be cracked.
SHA1 is not even anywhere close to "enough" for general password hashing use. Don't think otherwise just because a couple of random HNers failed your little game.
edit: The premise of your "challenge" is also not equivalent to the goals of most hackers. Unless you are a specifically known and prioritized target (because you're a celeb, VIP, wealthy person or something like that), the goal of a hacker is not to take one specific hash and crack it, because the success of that will depend a lot on the complexity of your password. The goal of most hackers in a breach like this Twitch one is more like "just throw it all at the wall and see what sticks". They take a massive database of thousands of hashes and spend a few hours to see what can be cracked, taking advantage of the fact that while some people may have complex passwords, most do not. After a few hours, maybe they crack 90% of the SHA1 hashes in a leak. Maybe your password was complex enough that it was in the 10% that wasn't cracked; good for you, but just because your password remained uncracked doesn't mean SHA1 is "enough". The hackers still got the other 90%.
Absolutely not and that is a ridicoulous conclusion to draw. State-level resources are absolutely not required to break sha1.
> but if your password _isn't_ cracked it's moot whether it's hashed with SHA1 or something more secure, as per above?
Again, absolutely not. The algorithm and cost setting have a huge impact on the practical likihood that an attacker will crack your password.
Even bcrypt is not that hard to find a solution to a hash if it didn't use enough rounds.
I learned a bunch of this when a company I worked for was breached and wanted to see just how easy it was to solve out weaker passwords in our db.
The LinkedIn password leak contained hashed (but not salted) passwords, and some of those where cracked and exploited in the wild.
My old gaming PC with a 1060 can apparently do ≈ 6300 * 10^6 hashes per second. Assuming your password above is az-AZ, 0-9 = 62 possibilities (with no salt) it would take me 10 seconds to test all combinations for 6 characters and 30 days for 9 characters. And it's a trivially parallel problem, making it easy to throw money on to make it wall-clock quicker.
It's just a simple brute force problem, I don't see what there is to question (beside the choice of SHA1 for password hashing...).
The hashes of previously unused passwords were brute forced, or passwords were reused across sites from a previous plain text dump and exploited? Because there's a big difference between those two things. If your password is reused and originally compromised , you're screwed regardless, and having the leaked hashed passwords doesn't leave you in any worse a situation than before.
> My old gaming PC with a 1060 can apparently do ≈ 6300 * 10^6 hashes per second. Assuming your password above is az-AZ, 0-9 = 62 possibilities (with no salt) it would take me 10 seconds to test all combinations for 6 characters and 30 days for 9 characters. And it's a trivially parallel problem, making it easy to throw money on to make it wall-clock quicker.
So practically infeasible to exploit? The claims that are being made (even in this thread) are that having a mining rig would let you brute force a SHA1 hash, but based on the numbers
> It's just a simple brute force problem, I don't see what there is to question
If it's "just a simple brute force problem", and SHA1 is the only issue, then my question is what's the password in the hash above? You (and others here, on reddit, online) are telling us that this is a trivial problem.
I believe there are documented instances where previously not leaked passwords were cracked. Of course not 128 bit random strings, but still passwords more "complex" than what you previously posted. If you have 100 million hashes to try, you will crack some. People are generally have bad passwords, especially in 2012, even if the plaintext weren't available anywhere...
> So practically infeasible to exploit? It depends on how strong the password is and how much money you have to spend. For 32 USD I get an hour with p4d.24xlarge that has 8 graphics card, that in total can do about 175 * 10^9 hashes per second. 20 hours (and 640 USD) machine time (not wall clock time) on that machine can do what 30 days on my old PC does.
> If it's "just a simple brute force problem" […] If you can give me a bound on the number of combinations, and an AWS account to bill, I and many others would gladly attempt to crack your hash :-). But if your second hash is >9 alphanumerical characters we will probably just burn electricity to no avail.
I don't even know what you are arguing?
EDIT: Now that you have some numbers of hashing rates and cost, you can figure out how expensive different passwords are to crack with different approaches. Two common dictionary words with two numbers appended? 6 random alphanumeric characters? Then think about how expensive the cheapest non-leaked password is in a database of 100 million users are...
Is it bad to store plaintext passwords? Yes, obviously. Is some hashing better than none. Yes, obviously. Is salting your hashes much better than not. Yes, because with a salt, your first password wouldn't have turned up on Google / in rainbow tables. Is it even better to use a proper PBKDF. Yes, with a pretty aggressive PBKDF, brute forcing even low-complexity passwords become expensive very quickly, and we get the benefits of salting "built in".
Can SHA1 / MD5 hashes be cracked even if not the _exact_ password-hash pair have been leaked previously? Yes, very much so.
I managed to lock myself out of a dogecoin wallet. I have the hash of the passphrase, so I figured I'd give it a go cracking it. After a few weeks (and a larger than usual power bill) I sent it to some friends with good mining rigs to try and take a stab at it, willing to split the amount 50/50. Its only the passphrase, not the full wallet, so I'm not worried about someone stealing the doge.
The passphrase is probably 15-25 characters, mostly not dictionary words or simple letter/number/symbol substitution, only symbols easy to type on a US keyboard. I'm now about 6 months trying to crack that password with probably a few hundred dollars of electricity used overall between myself and friends (I don't know their power bill), excluding hardware cost as it was already owned, and I'm not even halfway through the search space.
Can it be done? Sure. Will I be able to crack that password with a cost that's less than the value of the DOGE in the wallet? Probably not. Right now its really more of a gamble that I'll get lucky with the rigs running. I had to tone down some of my rigs as it was getting quite hot over the summer, but over the winter I'll be chugging away as the waste heat is just additional home heat. I'll probably need to rent a considerable amount of GPU power on a cloud provider to crack it, at which point maybe it'll take me days to crack it but ultimately cost me many, many thousands of dollars in GPU-time.