[TechniSol]

I don't know how the page number is stored internally with each firmware or app, but there must be a relationship between it and the file, so there should be no great obstacle to translating it to a universal value that can be interpreted on another device. One would assume(look out) that the same algorithms might have been migrated across platforms. If not, translation should be minimal, but requiring a different conversion on each platform.

As for identifying the book I'd suggest that whatever mechanism is employed in the internal database now would be sufficient, but, if not, the filename should be sufficient assuming the customer would have to use the same file on all their sideloaded devices. I'm not asking for content syncing, only page number syncing, and only for exactly the same files, not between kepub and epub formats or anything else...

If the data must be masked prior to transferring it to Kobo's servers, a common conversion or hashing algorithm could be used as long as Kobo never attempts to dehash or decrypt it anywhere but on the user's devices. It should slide in past any privacy requirements. Or if we need to make it complicated the user could enter a code or string used to perform the hashing and be required to enter it on their other devices so Kobo would never have the ability to decrypt the transmitted data as long as it never transmits the code or string used -assuming Kobo doesn't feel the need to employ cryptographic analysis techniques to figure out the hash or encryption key used. Let's be honest, the requirement for the filename of the book to be obscured doesn't have to defy cryptographic analysis as long satisfying privacy is only a minimal concern.

I'm just trying to open the same exact epub to the same "page" or thereabouts on differing devices. Personally, considering the difference in display size between a cell phone and a tablet plus or minus a page or two might be the best that could be done, but all this must have already been worked out to a great degree if it can be done for kepubs across platforms and devices...