I was trying to use Circus Ponies' Notebook for iPad with boxcryptor and Dropbox. (This is a note-taking app that also has a Mac counterpart.)
Problem is that when I create a new CP Notebook on iPad and sync it to the (boxcrypted) Dropbox, it seems to be "saved" to that directory rather than "uploaded". From a different post in this Forum (on saving text notes on the iPad with, e.g., Textastic) I concluded that when an iPad "saves" a file to the boxcrypted directory in a Dropbox, things go wrong; they need to be "uploaded".
Sadly, CP Notebook for iPad has Dropbox support included, so there is no way to "upload" something to Dropbox, rather the app thinks it knows how to sync to Dropbox (by "saving", I assume). The effect is that when I try to open the notebook document on the Mac (via boxcrypted Dropbox), I see some garbled, i.e., encrypted) stuff. Therefore, I cannot get it to work.