Certificate based software licensing?

Question

C++ / C#

In general, the question is this. What is the software licensing system based on?
I remember earlier I came across a scheme: A private certificate is generated, and on its basis short keys are generated that fit it but are not identical in set between each other. Does anyone know what it's called?
I even remember writing a shell script for generating and verifying, but unfortunately it was a long time ago and formatted :D

Answer 1

You can see here

Answer 2

In general, I decided by encrypting the secret key.