Oh, good point. I guess it depends on your usecase. I was thinking from the angle of not trusting premade network cards but trusting your USB chips.... which now that you point out, is also not a given. Maybe bare serial (just a wire per tx/rx), but it suddenly occurs to me that I don't know how that's actually connected to the CPU, and I think that approaching this from a security angle is a quick road to madness. OTOH... connecting a microcontroller to serial probably is the simplest option and as an engineering exercise is perfectly reasonable, if not exactly fast, but hey it's not like this was ever going to be performant.