The authoritarian governments may follow the approach that is being used against media piracy. They may arrest some random big fish and hand out extremely hard punishments, and then hope that it will deter others from dealing in cryptocurrency.
But, is it that easy to catch someone who is making use of crypto currency? I believe that people who are in China will be able to maintain their privacy and make use of cryptocurrency without being caught. We are all very aware that crypto currency is decentralized, and as long as you are able to maintain that peer to peer transaction then you are hardly going to have any issue with anyone.
The only time I think the government will be able to find you is when you are making use of it centralized exchange, where you are required to do KYC, then the government will have access to information about you and be able to know your whereabouts. But for people who maintain their privacy, they won’t be caught.