I read somewhere about the US trying to leak fake intelligence that they worked on some kind of military propulsion device. And leave just enough clues that if

I read somewhere about the US trying to leak fake intelligence that they worked on some kind of military propulsion device. And leave just enough clues that if someone tried this "at home", i.e. the Soviet Union, they would blow themselves up. And this was nicknamed or alluded to be "Red Mercury". Also see: https://en.wikipedia.org/wiki/Die_Glocke_(hoax) https://en.wikipedia.org/wiki/Die_Glocke_(hoax) which maybe was where the inspiration for the story (true or false) came from.