Securing a FZ-G1 Toughpad - Unlocking Encrypted Root

[dartleader]

Hey everyone, I'm trying to figure out how I can secure a Panasonic Toughpad FZ-G1 with a LUKS encrypted root partition.

As it has no keyboard, but six hardware buttons and a touchscreen/stylus, I'm not sure how I could input a password at boot to decrypt root.

Do I have any options aside from putting a LUKS key on a USB and inserting that at boot? There are limited combinations of keys I can assign to the hardware buttons in BIOS (F2, F12, etc).