Timeline for Does too long a salt reduce the security of a stored password hash?
Current License: CC BY-SA 3.0
8 events
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| Dec 21, 2014 at 18:49 | comment | added | Andrew Philips | @kasperd Fair enough - I shortened your answer a little bit. ;) | |
| Dec 21, 2014 at 18:03 | comment | added | kasperd | @AndrewPhilips That is the conclusion which my answer leads to. | |
| Dec 21, 2014 at 17:30 | comment | added | Andrew Philips | Just use a Salt the length of the hash code, it matches the max entropy of the hash and the password. Longer Salts do no good. Why worry about the storage size of the salt column in your (no)SQL storage? Total salt bytes grows linear with the size of your user base, which, in any realistic working system should be small compared to the amount of data stored for each (all) users. Sizeof(Authentication Data) << Sizeof(All other System Data). | |
| Dec 21, 2014 at 13:09 | history | edited | kasperd | CC BY-SA 3.0 |
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| Nov 26, 2014 at 9:58 | comment | added | kasperd | @Jens If that was the case it would be considered a major weakness in the hash function. It is recommended to use a hash function without known weaknesses. The password hashing can be structured such that the risk of the scenario you describe is minimized, even if the hash turned out to be weak. For example one could simply put the salt before the password and compute: h(salt || password) | |
| Nov 26, 2014 at 9:24 | comment | added | Jules | @Jens Yes. We usually pick hashing functions that exhibit the avalanche effect, which means that (ideally) changing any single bit in the input (or adding a single extra bit) will cause approximately half of the bits in the output to change. Therefore the password, even if it is just 1 bit long, causes as much change to the output of the hash as changing the entire salt for a new one would, regardless of its length. | |
| Nov 26, 2014 at 7:27 | comment | added | Jens | So, adding a really really long salt to the password will never "drown out" the password to some degree, making it easier to find a password with the same hash? Is this a property of the hash functions we use? | |
| Nov 25, 2014 at 20:52 | history | answered | kasperd | CC BY-SA 3.0 |