The North Koreans are not that advanced to make technology like this, I will be surprised if most of their weapons are freely given to them by the Russians.
Even if the Russians gave the Koreans nuclear weapons (I think so) this is not enough. The maintenance of these weapons very difficult task and perhaps it is no longer able to bear the damage which is expected of him by the Koreans. Russian are experiencing problems with the maintenance of their missiles. Korea is a big bubble that will burst after the first shot.