Well, actually, for a missile delivered Plutonium derived bomb that relies on staged shape charges to implode the core, causing the chain reaction, the electronics are quite complicated due to the extremely precise timeing required. Those electronic plans most likely also contain the fusing arrangement. That Iran has them doesn't worry me too much, as they lack sufficient plutonium to build lightweight nuclear weapons at the moment. Though if they get a breeder reactor up, that will change quickly.
North Korea on the other hand has plenty. Though they likely already have similar level plans aquired from China.