Secret file vault for iPhone and Mac? Is there a simple encrypted file vault for iPhone and Mac that share the same content, w/o third party server?

This is the use-case: I have certain files (texts and images) that I want to be protected. On Mac, I can create encrypted disk and mount when I need the files. This works fine. However, what I want here is an app that works both on iPhone and Mac, since I want to use files on my iPhone as well. Preferably w/o third party, but if encrypted I allow using e.g. Dropbox etc.

Here is a scenario:


I open this vault on Mac. Put some file in there. Close the vault.
Things get synced
On my iPhone, I open the same vault and there I can browse files.


There are many apps that do this, but they are either for Mac OR iPhone. I want a solution that works across the devices.
Cryptomator allows you to encrypt data stored in the usual clouds and access it from both Mac and iPhone.