4 ms·
I'm not sure how modern hashes fare in this regard, but one issue is that hashing a hash reduces your input space from all possible passwords to all possible ha
by jon_richards 9y ago
I'm not sure how modern hashes fare in this regard, but one issue is that hashing a hash reduces your input space from all possible passwords to all possible hashes of the first hasher.
- BenjiWiebe 9y agoIn my experience, it wouldn't be a reduction. I.e. most passwords are shorter than most hashes.
- whoami_nr 9y agoTechnically, it does actually. Suppose we use SHA-256 as first hashing algorithm, the input space for the second is effectively reduced to the 256 bits of output from the first which is much smaller compared to the input space of the first algorithm.
- concede_pluto 9y ago38 characters of ASCII gibberish (all 95 printable characters) gives you less than 2^256 possible passwords, and pretty much nobody uses a password with more entropy than that.
- jon_richards 9y agoThe problem is that you aren't just dealing with "any output from the first hashing algo", since passwords are going into that algo in the first place. A hashing algo can't add entropy, but collisions can reduce it.
- concede_pluto 9y agoAn undetected I/O error is vastly more likely than even one accidental SHA-256 collision among billions of passwords. It's not quite literally impossible but I'd bet my car I never see it happen.