Quote from: systemv on July 10, 2017, 02:30:06 PM

It can be very unsafe in Windows. If you are very concerned about security - use Linux, no network connected, same size USB drive and do low level disk copy such as:

dd if=/dev/sdX of=/dev/sdY bs=2M

where sdX source, sdY target. Be careful, that will destroy everything on sdY

What if /dev/sdX is a bigger drive than /dev/sdY and the key file happens to have been fragmented/moved to the end of /dev/sdX? And why not make bs equal to the underlying physical sector size? If running on a secure offline system you should just be able to use cp and skip the raw disk copy nonsense.