trying to create encrypted ephemeral drive on Amazon

[Brian Tarbox <ta...@cabotresearch.com>]

I've heard that on Amazon EC2 I should be using ephemeral drives...but I
want/need to be using encrypted volumes.

On my local machine I use cryptsetup to encrypt a device and then mount it
and so on...but on Amazon I get the error:

"Cannot open device /dev/xvdb for read-only access".

Reading further I wonder if this is even possible based on this statement
in the Amazon doc set "*An instance store is dedicated to a particular
instance; however, the disk subsystem is shared among instances on a host
computer*"

How are other folks achieving performance and encryption on EC2?

Thanks.