[setr]

I was counting the number of hashes to store; im not sure why the size of each character would matter?

But now that Im writing it out, I was clearly wrong anyways

I thinking something along the lines of taking every substring of 4 characters, and then for all permutations of those 4-tuples, plug it back into the string hash and store. Assuming the goal is to not share any 4-substring with the new string

So I think (N-4) + 1 gives you the number of 4-character windows

4! for the number of permutations of that 4-char window

So 4!*(n-3) total hashes

Which I guess is actually the same work you'd have to do anyways if you stored the plaintext; just without storing each variant