Security against a stolen device?

TLDR: Can I encrypt the SD card to protect my personal content if someone else gets a hold of the card?

I have a headless Pi 1 that I leave at my mother’s house and use as offsite backup. I store important photos, copies of passports, just in case my own house were to burn down (for example).

I got a bit of a scare recently: my mother did not remember the Pi was mine and turned it in to the internet provider when she was upgrading internet service (they asked for the old modem back and she thought the Pi was part of it). Luckily the technician recognized the Pi did not belong to the ISP and gave it right back.

This is obviously a pretty rare event. In retrospect, I should have clearly labelled the Pi as my own so that my mother wouldn’t mistake it (I have done so now). But this got me thinking, is the SD card protected in any way against viewing files that are stored on it?

I have a password on my OSMC account, but I am not sure if a user could just pop the card into a computer and read my files that way? It looks like gibberish (to me) on my Windows 7 PC, but maybe not on Linux etc? I understand that once a user has physical access, security prospects go way down - but I figure there is no reason to make it easy to a casual observer.

You can use filesystem encryption, possibly just for /home.

If you use it for the entire filesystem, the initramfs would need adjusting to support this.

Thanks, Sam. Is this the method you had in mind: