Wow! A private file. Well sadly, no matter how you cut it, we're working on a literal platform of 666 from the days the arpanet was created.
If it is in cloud storage, they can tamper. If they have a way in, they Can tamper.
Just like Bezos actually owns the servers steemit is hosting on, unless that has changed.
Bezos doesn't like truth tellers, so I always figure it's just a matter of time.