You are partially right. Not about the banking system (which is as much a joke and tool of the NK government as the currency), but insofar as you are better off if most of your assets are in the form of rice or some other physcial commodity. On the other hand, it's pretty likely that having more than a certain quantity of any commodity outside a government-operated warehouse is classified as 'illegal hoarding' and would be grounds for confiscation and imprisonment. North Korea practices such an extreme form of socialism that private property is a meaningless concept there. For all practical purposes it is a feudal society which claims all people, land and commodities as state property.