7 ms·

A few things here. If you're the sort of person who runs a crypto mine, which I assume many of the people interested in breaking hashes are you have enough fire

A few things here. If you're the sort of person who runs a crypto mine, which I assume many of the people interested in breaking hashes are you have enough firepower at your disposal to at least perform a targeted attack on a few hashes with relative ease. Ideally that would be useless because things are properly salted and you don't know the salt, however with access to all of the source code as we have here I think it isn't as clear cut, as it may be possible to reverse out the salts as well. I'm not a cybersec guy so please take my speculation with a grain of salt.

maccard 5y ago
I've heard this before, and queried how feasible an attack would be, as people always talk about just how bad this is but yet I've _never_ heard of someone having an account compromised through this vector, and I'd like to know how feasible it really is. Here's the sha1 of an unsalted password b85ffa7dae2cbed04e7d3335f6ebc43c8a5764dd How long does it actually take in practice to break something like this? I would love it if someone could prove it to me.
- jaredsohn 5y ago
  Is the password ncc1701e? I just googled it and found https://hashtoolkit.com/decrypt-sha1-hash/b85ffa7dae2cbed04e7d3335f6ebc43c8a5764dd https://hashtoolkit.com/decrypt-sha1-hash/b85ffa7dae2cbed04e... along with other results.
  - maccard 5y ago
    It is! I guess using a password from Google isn't the best idea, and kind of defeated the point of what I wanted to ask (if your password isn't already hashed online how long does it actually take to break a sha1 hash), but definitely proves the point. Can I try again? Sha1 e7b7cdf949007abe7e8a190ba8eae56c60018c1f
    - Behemoth66 5y ago
      Couldn’t find it in 1.4 Trillion combinations. Used rockyou.txt with dive.rule. 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.
      - maccard 5y ago
        Thanks for trying! This somewhat supports what I'm suggesting - because that password hasn't been leaked by being posted in plaintext as a verified password, it's not available as a lookup, therefore it doesn't matter whether they used bcrypt, sha1 or md5, or even just pgp encrypted it, the password is likely "secure".
        Behemoth66 5y ago
        It depends. It doesn’t have to strictly be a leaked password. If it’s similar to a leaked password then the permutation rule-set will catch it. 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_$@618jg then it doesn’t really matter how you hash it.
        maccard 5y ago
        The reason I didn't give any more information on the password above is because you don't have any extra information on a dump of hashes from a twitch database either. If a password is only feasibly brute forceable for a specific algorithm by reducing the search space by many orders of magnitude, it kind of shows that there's not really any risk even if the passwords are unsalted for a person who hasn't reused a password.
        thaumasiotes 5y ago
        > it kind of shows that there's not really any risk even if the passwords are unsalted for a person who hasn't reused a password. No, it doesn't. You could reuse uwv&6qu_brusb618_$@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.
- isoskeles 5y ago
  Many hashes are trivial to target, until you start getting to password hashers that force you to use lots of RAM or CPU (or ideally both) to check a single password. As long as you know what hashing algorithm was used (often inferred by the hash length or other details), you can shove it into hashcat or some alternatives and wait, either using a good dictionary or bruteforce. If you've configured hashcat to work well with a decent GPU, you're good to go. 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.
  - maccard 5y ago
    As I said, I've heard the claim, but still question it. Here's a sha1 e7b7cdf949007abe7e8a190ba8eae56c60018c1f, how long does it take hashcat to break it?
    - filleokus 5y ago
      I don't really follow your argument. You've never heard of a hash being brute forced? I've done it myself multiple times, both for pen testing purposes and for password recovery on systems I control myself. 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...).
      - maccard 5y ago
        > The LinkedIn password leak contained hashed (but not salted) passwords, and some of those where cracked and exploited in the wild. 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.
exitheone 5y ago
The salt is usually stored next to the password. The point of a salt is just to make the hash unique to prevent the use of rainbow tables, it's not a separate secret.
shkkmo 5y ago
I think it is pretty common to store the salts alongside the password hashes. They are used by the same pieces of code so it is generally unrealistic to think that your salts will be secure if your hashes are obtained. Salting isn't really supposed to make a hashing algorithm secure by being secret but by being unique. Unique salts make hashing more secure because an attacker can't re-use a single rainbow table for multiple hashed passwords. That, combined with a sufficiently computationally difficult hashing algorithm, it makes it prohibitively expensive to reverse the hashes of all your users. This may not be enough to protect high value users or those who use fairly common or easily guessable passwords. This is part of why it is so important that you don't reuse passwords. It's also why your application should reject all known passwords using something like https://haveibeenpwned.com/Passwords https://haveibeenpwned.com/Passwords or any of the "common password" list you can find online. Edit: If you do include a secret that is stored seperatly that is added to the password and salt when hashing, this is called "peppering" and these peppers are generally not unique per user.
Deathmax 5y ago
Salts being exposed is not a massive risk in of itself, as the purpose of the salt is to prevent the use of pre-computed tables to reverse a hash into plaintext, forcing an attacker to bruteforce each individual hash+salt instead of being able to reuse work. With regards to crypto mines being used for breaking hashes, if you have one based on GPUs, yes, you could reuse GPU mining hardware for cracking hashes, albeit with relatively low hashrates for current best practice hashing algorithms. If you're looking at something like Bitcoin's hashrate and thinking that it could be used to break SHA2 hashes, as far as I understand ASIC miners, this is not possible, as ASIC miners are designed only for mining, and they don't really accept non-mining related inputs (ie, no arbitrary inputs to be hashed, unless it matches Bitcoin's specific steps for iterating over nonces).
thaumasiotes 5y ago
> Ideally that would be useless because things are properly salted and you don't know the salt I'm really curious where people get their ideas about salting. It's not just a word. It doesn't make one password any more difficult to crack. It makes cracking every password in a given database more difficult to do. A password's salt is public information.

maccard 5y ago

I've heard this before, and queried how feasible an attack would be, as people always talk about just how bad this is but yet I've _never_ heard of someone having an account compromised through this vector, and I'd like to know how feasible it really is. Here's the sha1 of an unsalted password b85ffa7dae2cbed04e7d3335f6ebc43c8a5764dd How long does it actually take in practice to break something like this? I would love it if someone could prove it to me.

jaredsohn 5y ago
Is the password ncc1701e? I just googled it and found https://hashtoolkit.com/decrypt-sha1-hash/b85ffa7dae2cbed04e7d3335f6ebc43c8a5764dd https://hashtoolkit.com/decrypt-sha1-hash/b85ffa7dae2cbed04e... along with other results.
- maccard 5y ago
  It is! I guess using a password from Google isn't the best idea, and kind of defeated the point of what I wanted to ask (if your password isn't already hashed online how long does it actually take to break a sha1 hash), but definitely proves the point. Can I try again? Sha1 e7b7cdf949007abe7e8a190ba8eae56c60018c1f
  - Behemoth66 5y ago
    Couldn’t find it in 1.4 Trillion combinations. Used rockyou.txt with dive.rule. 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.
    - maccard 5y ago
      Thanks for trying! This somewhat supports what I'm suggesting - because that password hasn't been leaked by being posted in plaintext as a verified password, it's not available as a lookup, therefore it doesn't matter whether they used bcrypt, sha1 or md5, or even just pgp encrypted it, the password is likely "secure".
      - Behemoth66 5y ago
        It depends. It doesn’t have to strictly be a leaked password. If it’s similar to a leaked password then the permutation rule-set will catch it. 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_$@618jg then it doesn’t really matter how you hash it.
        maccard 5y ago
        The reason I didn't give any more information on the password above is because you don't have any extra information on a dump of hashes from a twitch database either. If a password is only feasibly brute forceable for a specific algorithm by reducing the search space by many orders of magnitude, it kind of shows that there's not really any risk even if the passwords are unsalted for a person who hasn't reused a password.
        thaumasiotes 5y ago
        > it kind of shows that there's not really any risk even if the passwords are unsalted for a person who hasn't reused a password. No, it doesn't. You could reuse uwv&6qu_brusb618_$@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.
isoskeles 5y ago
Many hashes are trivial to target, until you start getting to password hashers that force you to use lots of RAM or CPU (or ideally both) to check a single password. As long as you know what hashing algorithm was used (often inferred by the hash length or other details), you can shove it into hashcat or some alternatives and wait, either using a good dictionary or bruteforce. If you've configured hashcat to work well with a decent GPU, you're good to go. 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.
- maccard 5y ago
  As I said, I've heard the claim, but still question it. Here's a sha1 e7b7cdf949007abe7e8a190ba8eae56c60018c1f, how long does it take hashcat to break it?
  - filleokus 5y ago
    I don't really follow your argument. You've never heard of a hash being brute forced? I've done it myself multiple times, both for pen testing purposes and for password recovery on systems I control myself. 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...).
    - maccard 5y ago
      > The LinkedIn password leak contained hashed (but not salted) passwords, and some of those where cracked and exploited in the wild. 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.

exitheone 5y ago

The salt is usually stored next to the password. The point of a salt is just to make the hash unique to prevent the use of rainbow tables, it's not a separate secret.

shkkmo 5y ago

I think it is pretty common to store the salts alongside the password hashes. They are used by the same pieces of code so it is generally unrealistic to think that your salts will be secure if your hashes are obtained. Salting isn't really supposed to make a hashing algorithm secure by being secret but by being unique. Unique salts make hashing more secure because an attacker can't re-use a single rainbow table for multiple hashed passwords. That, combined with a sufficiently computationally difficult hashing algorithm, it makes it prohibitively expensive to reverse the hashes of all your users. This may not be enough to protect high value users or those who use fairly common or easily guessable passwords. This is part of why it is so important that you don't reuse passwords. It's also why your application should reject all known passwords using something like https://haveibeenpwned.com/Passwords https://haveibeenpwned.com/Passwords or any of the "common password" list you can find online. Edit: If you do include a secret that is stored seperatly that is added to the password and salt when hashing, this is called "peppering" and these peppers are generally not unique per user.

Deathmax 5y ago

Salts being exposed is not a massive risk in of itself, as the purpose of the salt is to prevent the use of pre-computed tables to reverse a hash into plaintext, forcing an attacker to bruteforce each individual hash+salt instead of being able to reuse work. With regards to crypto mines being used for breaking hashes, if you have one based on GPUs, yes, you could reuse GPU mining hardware for cracking hashes, albeit with relatively low hashrates for current best practice hashing algorithms. If you're looking at something like Bitcoin's hashrate and thinking that it could be used to break SHA2 hashes, as far as I understand ASIC miners, this is not possible, as ASIC miners are designed only for mining, and they don't really accept non-mining related inputs (ie, no arbitrary inputs to be hashed, unless it matches Bitcoin's specific steps for iterating over nonces).

thaumasiotes 5y ago

> Ideally that would be useless because things are properly salted and you don't know the salt I'm really curious where people get their ideas about salting. It's not just a word. It doesn't make one password any more difficult to crack. It makes cracking every password in a given database more difficult to do. A password's salt is public information.