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You can't unhash, so you could never retrieve the original file again.

What do you mean? You obviously store the encrypted file together with the encrypted hash.

Then I guess me and the downvoters thought you meant hashing the files for encryption :)

two people have downvoted me without explanation

Sadly, that is the new normal for HN (and, I'll be downvoted for saying something like this)

You could also hash, encrypt, then hash again if you wanted extra integrity without decrypting. This is technically done with HTTPS through the TCP hash.