Demonetization. Not the kind seen in India though. Spread it over 3-5 years like we did with old banknotes. Eliminate physical cash above a 100 rupees. Get a phone manufacturer involved to put 7000-8000 rupee smartphones in the hands of people (everybody can afford this even my garbage collector) and shift to digital payments that is linked to your ID card. Lower internet prices so that people are always "on". You eliminate at least 90% dirty money with this approach, end money laundering and the careers of many journalists in one go. Easier said than done though, Mariam nani would explode at the nearest chowk just to stop this from happening.
