Well, they could trade identifying ones too or even stollen ID cards if you want to go this way.
replyThey could also trade porn-filled thumb drive or old-school glossy paper magazine. There no way to prevent kid's exposure to stuff at a 100% success rate.
There no way to avoid exposure completely
Indeed but you are the one who claimed it was not a hard problem.
replyI don't think any one of us pushing back here on those claims do so for the heck of NOT finding a "solution", rather genuinely asking because so far it seems nobody did find such a solution without compromises that is in the end not worth it due to the flaw in said solution.
The point isn't to be critical of your process, only of the claim that it's a trivial problem.