I am about finished with my game for android made using Mono for Android and MonoGame. My game's code has several hard coded strings such as billing service key, Facebook app key, ad service key and so on. I have personally never dealt with any facet of software security, but I understand that it might be very easy for even the hobbyist cracker/hacker to get these strings. After searching online, I understand that there is no perfect solution for securing those strings. But I know am not the first to face such a problem, and would like to know about the basic methods that most software out there use to at least obscure those strings and make them only available to those determined to get them. If you know of such method (maybe it is already provided by some class in a .net library?), please provide a code snippet since I am really no expert in security(Prefer a cross platform method). Thank you.
Here is an example of code that occurs in my app: (the key(fake) I want to hide is the last argument)
BillingService = new BillingService(this, this, "Sdsawfcdsvcgfh23sdlKfasdjw");