Uh, what? You can obviously crack a hash digest, and this is standard nomenclature used in both industry and academia. It simply means you've broken preimage re

Uh, what? You can obviously crack a hash digest, and this is standard nomenclature used in both industry and academia. It simply means you've broken preimage resistance or collision resistance in practice. What exactly do you find controversial about this? And your second paragraph doesn't follow. What I said isn't a strawman attack, it's a basic observation. If you're not using a secure key derivation function, a private salt will not save you. If you are, the salt can be public and there is no meaningful degradation in security whatsoever - you could even prepend or append it to the digest if you'd like. As a broader point, what you're saying about fixed-length strings is incorrect. Hash functions need not output strings of fixed length. The formal definition of a hash function also admits functions of the form: H: {0, 1}^* -> {0, 1}^* not just functions of the form: H: {0, 1}^* -> {0, 1}^n. Or in other words, the codomain need not be finite, and the range can be variable. Keccak (SHA-3) is an example of a hash function which provides variable-length output instead of fixed-length output (i.e. via the sponge construction).