Apparently using full-disk encryption is not enough to secure a computer, because the /boot partition is not encrypted, and could be modified to include a keylogger.
I have read about different counter-measures, but the only one that didn't sound too complicated and I actually understood was moving the /boot partition to a USB pendrive which I should carry with me all the time and use it to boot.
So how do I do that? I'm using Fedora 17, 18, and Ubuntu 12.04.
Any other suggestions?