I would like to automate file encryption on my Android device before sending them to a cloud storage.
I don't want to have a container encryption (like Truecrypt or VeraCrypt) since it will require a lot of data to be transmitted on each update, lots of resources to check changed blocks, and I don't see this is a good way approach to automation for such a task. So it will be better to have encrypted version of each file.
Moreover, I would prefer public-key encryption (asymmetric), not based on password strength. And most important - I would like to be able to work with files on different platforms (not only on Android).
I found that Encdroid is quite close to my needs (except that it is not asymmetric encryption): it is based on Encfs that works on different platforms and it is per-file encryption file system. The biggest drawback is that it requires FUSE module (filesystem in user space), which is not usually available on most Android distributions.
Another option will be to adapt GPG for that task, but it will require some scripting and probably other tasks that Android is not usually suits to. And I don't know if GPG works good on Android.
Do you know what are options to solve this task?