That's true, but it would be equally true of a backdoor inserted at the foundry by the technique described in TFA. Also, it is possible to insert back doors in

That's true, but it would be equally true of a backdoor inserted at the foundry by the technique described in TFA. Also, it is possible to insert back doors into hardware in ways that would be very hard to spot even by people familiar with the design. I've seen automated design tools emit some pretty weird shit, and for all I know it might have been a back door. But it passed LEC and DRC so it shipped.