I don't use rsync. Because it's for synchronization and I don't really trust any of my storage drives to hold a perfect copy of data to sync from and act as an ultimate source of truth for connected, downloading clients. I especially don't really trust flash memory storage devices.

The only source of truth that is really reliable is a password memorized in your brain. Because keyfiles that can decrypt data can be corrupted, that is to say, they rely on a secondary data integrity check. Like the information memorized in your brain.