The “what” of North Korea’s nuclear weapons is a known thing. It’s a copy of a 1960’s Polaris missile. An old US design. This design was copied by Israel, France, Russia and China; probably even India. It is also the Israeli Jericho 2 design, copied from the Polaris A1 design. The UK also had it in their older nuclear submarines.
The good news is that the warhead does not separate from the missiles’ main body, so it’s easy to intercept. The re-entry platform is quite crude. The bad news is that with 150kt yield, it’s still dangerous.
What puzzles most analysts is how fast North Korea got from rudimentary designs to this latest improved version. In other words, who has been helping them.
The notion that it’s Iran is pretty bizarre. Iran doesn’t have a nuclear bomb. It seem to make more sense to look at who does have them and see who would have an interest in North Korea having one too.
This site below makes a strong argument that it’s China. This is the part of the post that drops down from knowledge to mere information. It’s a good argument, but for now I don’t know. You would think our zillion dollar intelligence agencies would have an answer.
If you are a conspiracy minded person, you might be inclined to believe that they do know. Read more here.