Comment 3 for bug 1215504

This would be a very useful feature. I avoid using persistence due to security concerns if the usb is lost and things line my Ubuntu One login were on it. (which has happened to me.) The fix looks trivial to me and I'm sure it would get a lot of usage if available and known.

This article covers the change needed.
https://archimedesden.wordpress.com/2013/09/12/encrypted-persistent-storage-on-ubuntu-livecd/