3 ms·

If your first two statements are correct I can't see how the third can't be. If we choose our password from only ~24 chars then you can get the same effect of

If your first two statements are correct I can't see how the third can't be. If we choose our password from only ~24 chars then you can get the same effect of 100K iterations form just 4 more characters, or ~1 more dictionary word. That doesn't seem excessive

TylerE 4y ago
10ms (or whatever) of computer time is a lot cheaper than 2 seconds of mine
- Aicy 4y ago
  Not for the company paying for the compute
  - Tostino 4y ago
    2 second login times can drive away enough customers to make it be the case.
kadoban 4y ago
Increasing the iterations is basically free (up to the point where it requires human-noticable amounts of time to calculate), so there's no need to require 4 more characters. Also, teaching users enough of this to do it well is basically impossible. You have to have a threat model that includes your users being fairly shit at passwords. Especially when your product is solving the problem of users being shit at passwords.
KMnO4 4y ago
Imagine you're an adversary, and you've just stolen a list of hashed passwords. The values you see are: ae1fb1a0b0ee --> ??? f10abddc10a0 --> ??? What you're going to do is start bruteforcing letters until you find the matching passwords. You know that the passwords are hashed with 100k iterations, but you don't know how long the password is. First you start with a, b, c, d, ... z. That's 26 combinations. Then you do aa, ab, ac, ad, ... zz. That's another 26^2 (676) combinations. The next length of aaa, aab, aac, ... zzz is >17k combinations and it keeps increasing exponentially. Increasing the number of iterations applies a linear multiplier to the time. If it take 26ms to bruteforce all the one character hashes with 1000 iterations, it will take 2600ms with 100,000 iterations. But increasing the password length adds a multiplier of 26 with each new character (and that's only assuming single case letters). Adding 4 extra letters is actually an improvement of over 450,000x (26^4). (Assuming you are using the printable ASCII character set, that's actually 95^4 = 81,450,635x)

TylerE 4y ago

10ms (or whatever) of computer time is a lot cheaper than 2 seconds of mine

Aicy 4y ago
Not for the company paying for the compute
- Tostino 4y ago
  2 second login times can drive away enough customers to make it be the case.

kadoban 4y ago

Increasing the iterations is basically free (up to the point where it requires human-noticable amounts of time to calculate), so there's no need to require 4 more characters. Also, teaching users enough of this to do it well is basically impossible. You have to have a threat model that includes your users being fairly shit at passwords. Especially when your product is solving the problem of users being shit at passwords.

KMnO4 4y ago

Imagine you're an adversary, and you've just stolen a list of hashed passwords. The values you see are: ae1fb1a0b0ee --> ??? f10abddc10a0 --> ??? What you're going to do is start bruteforcing letters until you find the matching passwords. You know that the passwords are hashed with 100k iterations, but you don't know how long the password is. First you start with a, b, c, d, ... z. That's 26 combinations. Then you do aa, ab, ac, ad, ... zz. That's another 26^2 (676) combinations. The next length of aaa, aab, aac, ... zzz is >17k combinations and it keeps increasing exponentially. Increasing the number of iterations applies a linear multiplier to the time. If it take 26ms to bruteforce all the one character hashes with 1000 iterations, it will take 2600ms with 100,000 iterations. But increasing the password length adds a multiplier of 26 with each new character (and that's only assuming single case letters). Adding 4 extra letters is actually an improvement of over 450,000x (26^4). (Assuming you are using the printable ASCII character set, that's actually 95^4 = 81,450,635x)