You could hash the file contents plus a salt that is contained within the application binary. Most people wouldn’t know how to extract the salt from the binary

You could hash the file contents plus a salt that is contained within the application binary. Most people wouldn’t know how to extract the salt from the binary so they could get the hash right. Though I guess if people are determined enough to hack your game, one hacker might just publish the salt or a small program to rehash files for you. If a user has enough time on their hands, there’s nothing you can do to stop them from running your software in a VM with a debugger and finding out its secrets; the best you can do is making that hard enough that people won’t bother.