How to store in-game currency in iOS

Question

I am creating an iOS app with in-game currency. What is the best way to store the in-game currency? I am looking for something that jailbreakers can't access/change, something persistent, and something fast.

I have looked into Core Data, as well as perhaps NSUserDefaults. Can anybody suggest the best method?

Answer 1

My recommendation would be to follow iTukker's recommendation above and store them in the keychain.

But I wanted to add some additional info:

Anything that you store or calculate locally (meaning in the device) could theoretically be tampered with. No solution can offer you the level of security that calculating and storing those values server-side would. And even then, there's always the chance to fool the server into giving you more rewards through other means.

What I mean to say is that you have to look for something that's "good enough" rather than completely secure. What "good enough" is, depends on you.