Remember when Microsoft would trash Linux because it was open source and "not secure." Well, this settles it. Using your own hardware and open source software helps but someone determined will still get in...
working with chipmakers to insert back doors
So you're going to need to make your own chips, too.
http://www.cl.cam.ac.uk/~sps32/sec_news.html#Backdoor
> Abstract. This paper is a short summary of the first real world detection of a backdoor in a military grade FPGA. [....] The backdoor was found to exist on the silicon itself, it was not present in any firmware loaded onto the chip. [....]