[U-Boot] Secure update of uboot devices?

[Andreas Bäck]

With the new threats like Stuxnet and Duqu one need to improve on how new
updates to software is distrubuted to devcies so one can
be sure that it's not a hacked or modified software that runs in the
device. We use uboot + usb stick to update the software in our devices.
Have anyone been trying out to add e.g cryptated,certificates or rsa keys
to uboot?