In general you can't, and you should probably focus your effort in making a compelling game rather than preventing cheating. People can cheat in many types of games, and mostly they don't (particularly if it's single-player).
I respectfully disagree. I agree that some hackers will see the challenge as appealing, but obfuscation as a security technique has been proven a successful deterrent It will remove an entire class of hackers from wanting to hack your game. It's the same reason encryption algorithms use a cypher. Sure, a talented hacker with a lot of time on their hands could discover the cypher and crack the algorithm, but it will deter lower level hackers who dont have the skills to crack the cypher, and the hackers who dont feel like putting in the time to crack it. You cannot prevent 100% of all hacking, it's about staying 1 step ahead, and putting hurdles in their way.