How to understand the cryptography task "The key is created by a non-linear mixture of ... generators"?

Question

Cryptography

I was given a job in cryptography.
I understood how to make generators (linear and quadratic), but I don’t understand how to take them and “mix non-linearly”.
Google is silent (or I don't know how to google).
Tell me, please, how can this be done?

Answer 1

I think you can take any non-linear function with, say, two variables and use the values ​​of the generators as the values ​​of the variables. The value of the function will be non-linearly mixed from the values ​​of the generators. I can be mistaken, what the teacher meant only he himself knows.