You could, however what happens if an author does not post a hash? If I found someone else's paper without a hash, I could generate a hash of my own and claim a

You could, however what happens if an author does not post a hash? If I found someone else's paper without a hash, I could generate a hash of my own and claim authorship. This idea would only work if everybody started securing some form of proof of authorship before sharing papers with anyone, which I don't quite see happening.