[CoLoCo] Ubuntu Encryption Question

[Ringo]

Hey Ubunteristas/os,

I teach a workshop on computer security and I got a question from
somebody that I didn't know how to answer. I often tell people that
Ubuntu's built-in full-disk encryption available on the alternate
install CD is awesome, which it is.

Somebody was asking me if you could set it up to use a keyfile on a USB
stick, a CD, or something like that. Has anybody had any experience with
this? I imagine that you can set this up via a live cd once you've set
it up, but will it recognize hardware that early on? Also, how strong is
the encryption and can the strength be changed any way except manually
re-encrypting everything through the LiveCD?

Thanks for any help you can offer,
Ringo