Is it possible to calculate a document hash from office.js

My team and I would like to get a hash (MD5/SHA whatever) of a document using Office.js in an Office add-in context.

The idea is that if the user has a document on their local computer that matches a hash of a document on a server, the add-in is able to detect this and notify the user.

We found Office.context.document.getFileAsync which has a CompresedFile option which seems to be supported by most platforms - if I hashed the bytes returned by this function would it be the same as hashing a file on disk, or is there some other transformation that occurs?