All you need is a valid license, permit, CPL, (whatever your state calls it) issued by your state. Indiana law is silent on OC/CC. There is nothing in the code that specifically says how you must carry. However, there are times when someone that is OC'ing will attract attention. Police interaction varies from city to city. Some police don't care if you OC, others have been known to show their lack of knowledge concerning OC in Indiana. While you may be stopped by law enforcement and be asked to see your "permit", once you have proven you are legal, the stop (and any subsequent questioning) SHOULD end. The keyword is "should".
By the way, IANAL.