Develop a Private package in Flutter

Developing a flutter plugin which I want to share with my customer but I don’t want to share my code logic. What should I do to achieve that?

The simple scenario is that my client will call the plugin and pass his parameters in it and then my plugin will return a value based on the values given.

i.e

input a = 2
input b = 4
output = 6

Here I am adding a + b but don’t want to show my client a + b logic.

Any help will be appreciated.