The Ubuntu Live CD is not really fit for the task described. I suggest the use of Tails - it supports encrypted volumes, may be burned to a CD/DVD, installed onto a USB disk, and so on. It is designed to ensure that the network fails closed, so if the system was accidentally online, it would only connect through Tor. This also gives you native Tor support without any configuration.
The Ubuntu Live CD is not really fit for the task described. I suggest the use of Tails - it supports encrypted volumes, may be burned to a CD/DVD, installed onto a USB disk, and so on. It is designed to ensure that the network fails closed, so if the system was accidentally online, it would only connect through Tor. This also gives you native Tor support without any configuration.