Why Currency Revaluation in North Korea ?

This article states it was aimed at wiping out an emerging middle-class (or bourgeoisie).

This social strata is developing because of policies that permit private markets as a way to boost production. Those with moderate amounts of private capital are now wiped out. State connected 'elites' have their money in foreign banks or foreign denominations, and are unaffected. Likewise, workers and pesants basically have no money or saved capital, and are likewise unaffected.