OS X, keychain. store data that can be only changed by my app, not by user, or other app

Question

On iOS we use keychain to store information about in app purchases. (so user cannot change them ).
We now port our app to Mac (publish it in Mac App Store).
Can we use Mac keychain to store in app purchases?
Can we protect keychain data in some way?
We want that only our app can change values in keychain, not other apps or user.

Answer 1

other apps cant access the keychain without asking the user

the user can always change the data - on ios and osx both

except that on osx it is REALLY easy and on ios it isnt ;)