Here is the text of the NIST sp800-63b Digital Identity Guidelines.
I don’t know about a min length; setting a lenient lower bound means that any passwords in that space are going to be absolutely brute force-able (and because humans are lazy, there are almost certainly be passwords clustered around the minimum).
I very much agree with the rest though, it’s unnerving when sites have a low max length. It almost feels like advertising that passwords aren’t being hashed, and if that’s the case there’s a snowball’s chance in hell that they’re also salted. Really restrictive character sets also tell me that said site / company either has super old infra or doesn’t know how to sanitize strings (or entirely likely both)…
The only justifiable reason I can see to have a length limit is because longer passwords would take more time to process and they don’t want to deal with that.
Although it would only be on the order of a couple of extra microseconds and I’m not sure how much difference it would really make. But even on cyber security forums the max password length is 64 characters.
But it really doesn’t, unless you’re sending megabytes of text or something. Industry standard password algorithms run the hash a lot of times, and your entry will only impact the first iteration.
I usually set mine to 256 characters to prevent DOS attacks, and also so I don’t need to update it ever. Most of my passwords are actually around 20-30 characters in length (I pick a random length in the slider on my password manager), because I don’t want to be there all day if I ever need to manually enter it (looking at you stupid smart TV…).
unless you’re sending megabytes of text or something
That’s exactly what someone malicious would do though, either in a single password submission or DOS via the password maximum repeatedly. IMO there is no functional security difference between a 64 and a 256 character password, so the NIST 64 character max is reasonable.
