What i wanted to do is prevent my unity exe files from being copied/duplicate. Is it possible to have a lock or some sort of authentication. It can be a simple to read usb serial code to unable unity program. yes i know (2019) anything can be cracked. Thanks.
Any code that must be kept so secure that you cannot even trust your users with a compiled version should be executed on a server and accessed via RPC. Anything that runs on the client, you should assume a sufficiently motivated user can, will, and already has cracked, read, analyzed, and attacked. For a single player game, this is very rarely a concern. Any sort of physical (or for that matter, digital) DRM is going to do nothing but frustrate your honest users, and encourage the spread of cracked versions.