I've been thinking about this idea on and off for as long as I've been umm-ing and ahh-ing about a Car PC: to have the in car's disks encrypted. This would mean that if the PC is stolen, any data is protected, and there is also the supreme geekiness of the venture.
So far my car PC sitting on the floor in the house. I have some of the hardware... I need a pocket PC for the front end, various power stuff, and a case for the whole system. Oh, and a car :( Mine failed it's MOT, and it's uneconomical to fix. So I'm keeping half an eye on ebay and autotrader, and using my Mother's Honda Jazz in the meantime. It's a nice new car, but it's aimed squarely at the older driver, and it shows with its awful acceleration.
I don't really have much of an idea how to do an encrypted filesystem with Linux.... I've googled a bit and it looks like you use libcrypt and loop-back devices, and it seems there could be rather a lot of CPU overhead.
Ideally I'd plug a USB stick into the dash of the car, by the ignition, and this'd power on the laptop. My current machine (Tosh Portege 7020CT) can't boot from USB, so I guess I'd have to have an unencrypted /boot partition on the HDD. The machine'd boot, read the encryption key from the USB stick, decrypt and mount /, and carry on booting.
Has anyone done anything like this? I should think it'd be quite easy to fashion up a button/switch inside a USB socket, so this could be hacked into the power button on the computer. A script could halt the PC upon device removal.
I also plan to have automated music sync onto my car PC, by getting it to power on at night using a BIOS feature, connect to the home WLAN, and rsync with a server. With an encrypted filesystem, and the USB stick on my car keys, booting up would be a problem. The initrd would have to contain enough to get the PC onto the WLAN, then the filesystem encryption key could be loaded off the network.
As I said, I don't have a car of my own at the moment, and my first car PC is very must in development too, so I should think I'd try a fully encrypted system would be at least version 2 of my rig. But food for thought in the meantime :)