Re^2: SaltedDigest Salt?

[zwon]

Of course, if the bad guys get at your DB, then they get the hashes and the asscoiated salts, so its value deteriorates.

Value of salt is that it prevents attacker from creating rainbow tables, if disclosure of salt compromises security of your system it is poorly designed, that's exactly the reason why cleartext passwords are bad. Additional problem with common secret salt is that you can't change it once it leaked.

the more layers there are, the harder it is for them to crack through them all

The harder for you to analyse and verify your security model, the more lines of code, the more bugs.

[BrowserUk]

Value of salt is that it prevents attacker from creating rainbow tables,

It may prevent them from compromising all the accounts quickly, but it certainly does not prevent them from targeting selected accounts.

If the have both the hash and the salt, it becomes a matter of cpu cycles, and with AWS and other selling those so cheaply, it is just a matter of how much they are prepared to spend.

Value of salt is that it prevents attacker from creating rainbow tables,

I fail to see why? If you've been compromised, you surely need to change all the pass-phrases. At which point you have to rehash anyway.

I'm not saying a constant secret salt is a perfect solution, just convenient and relatively safe if done properly.

But then, there is no "perfect solution".

[zwon]

prevent them from compromising all the accounts quickly

No, it prevents them from quickly finding accounts with weak passwords

certainly does not prevent them from targeting selected accounts. If the have both the hash and the salt, it becomes a matter of cpu cycles, and with AWS and other selling those so cheaply, it is just a matter of how much they are prepared to spend.

Oh, really? Could you estimate how much it will cost to crack 16 characters random alphanumeric password (let's assume we're using SHA512)? And how many CPUs do I need if I want it this life? Maybe CPU cycles not exactly the right thing in this case.

[BrowserUk]

Start here and read to the end of the subthread.

Then read about bit-slicing, and vectorisation & parallelisation.

And when you think you're safe because those references all talk about Windows password schemes and piddly little 64-bit md5 hashes, go read about how a couple of hundred dollars spent on Field Programmable Gate Arrays make tackling your SHA512 hashes a realistic prospect.