On macOS at least, if you want to keep data encrypted, you can use encrypted disk images. If you want a more user friendly alternative, you can use https://www.

On macOS at least, if you want to keep data encrypted, you can use encrypted disk images. If you want a more user friendly alternative, you can use https://www.espionageapp.com https://www.espionageapp.com, which lets you encrypt folders (note: I wrote Espionage).