There's a silicon doping attack for CPUs which makes them impossible to verify with current verification techniques (as far as I understand). The idea is that i

There's a silicon doping attack for CPUs which makes them impossible to verify with current verification techniques (as far as I understand). The idea is that if you dope the silicon in the circuit you can change the circuit and it's not possible to figure out if it's been changed through forensics (x-rays, etc) or just using it (sufficiently clever backdoor). I'm unsure if FPGAs are vulnerable to this attack (though I've heard they might not be). This is the paper: http://sharps.org/wp-content/uploads/BECKER-CHES.pdf http://sharps.org/wp-content/uploads/BECKER-CHES.pdf