Boxcryptor doesn't really work consistently enough across devices and services to use in this way. For example, you can encrypt local storage on android phones, but not on iOS devices, despite Apple exposing the file system.
Also, what cloud services exist have to have an https implementation consistent with whatever evolving standard Boxcryptor decides upon. It really isn't useful in this sense.
I have not identified a way to solve what you are trying to solve. It seems file storage in the clear is what everyone accepts as correct.