Write a C# program from generating a decrypted binary

I have a program written in C# with its source code.the program takes a binary file as an input and encrypt it then send it through usb serial communication to a canbus device.
I have lost the binary that I used but I still have the source code of the C# program so I want someone to read the source code and the canbus encrypted binary data and figure out all the steps taken to encrypt the binary in order to make some function to generate the unencrypted binary
You have to be familiar with c# and encryption.also canbus is an added skill that can help but not that much.since you can figure out what the program is doing only by reading the source code and seeing what it does to the input binary
The payment will be only if the job is successful.that is by inputing the resulting file that you generated into the program again and see if the encrypted canbus data is the same as my log