How to generate a crypto key or something to identify the client?

Question

Cryptography

Task - I have a dll library that is installed on the client and does something useful there, it goes to my server for updated content. How to make it uniquely identify this library at the moment when it comes for updates, in other words, so that each client has its own unique copy of this dll. Updates cost money, so it needs to be difficult (impossible) for a client to modify a library to, for example, pretend to be another client's library and receive updates for another. How to solve the problem, in the direction of which technologies to look?

Answer 1

Wouldn't it be easier to store information that a client with such a unique ID has already received an update, and not reissue an update to him. Then the user who "shared" his distribution, dug a hole for himself.

Answer 2

If the dll is given to the user, then it is no longer possible to trust the information coming from this dll. Dig to the other side.