Question: Where can one find information on which areas of mathematics are represented at which of the more than 20 universities in the Democratic People's Republic of Korea (DPRK), and on which mathematicians are working there?
The DPRK is a country with a population of about 25 million people, and it is industrialised to a degree which has permitted it to successfully construct nuclear weapons and ICBM's. So one would expect that there are a decent number of mathematicians working at its universities.
However as the country operates an intranet of its own, not much from there is visible from the open internet. -- So in particular Google will not help much further here. Also, most results by researchers from the DPRK are published only in national journals, and mathematicians from the country cannot be found in the Mathematics Genealogy Database. On the other hand, people in the DPRK who need the internet for their work do have access, but with some sites blocked and email possibly monitored.
Edit: The possibly most interesting source available on the open internet I found so far is NKScholar. -- But firstly articles posted on that site are paywalled with prices in local currency, and secondly the site is Korean-language only -- so I can't tell how much one can really find there. Maybe someone else can tell more.
Added on Jan 22, 2019: As to the publications from the DPRK which have appeared in international journals: there are so far 118 articles with at least one author based in the DPRK which have reviews in MathSciNet. Of these, 101 are from the year 2012 or later. The articles touch 34 two-digit MSC numbers, and have been written by more than 100 distinct authors (where the exact number of the latter is not easy to determine due to slightly varying romanizations of names etc.) based at about 20 distinct institutions, mostly located in Pyongyang, the capital of the country. Among these articles, 41 have been co-authored with colleagues from China, 9 have been co-authored with colleagues from Germany and 4 have been co-authored with colleagues from other countries. The areas represented best are MSC 35: Partial differential equations and MSC 76: Fluid mechanics (together 47 papers) -- but also e.g. MSC 11: Number theory, MSC 16: Associative rings and algebras, MSC 26: Real functions, MSC 37: Dynamical systems and ergodic theory, MSC 53: Differential geometry, MSC 54: General Topology and MSC 55: Algebraic topology are represented with several papers, each. Given that there are almost as many distinct authors as there are papers, given the breadth of the areas covered and given that it doesn't seem likely that the country's mathematicians have started to work all of a sudden barely a decade ago, what is visible in MathSciNet seems merely like the tip of an iceberg to me -- which emphasizes the question about the "rest".