Convert existing iOS paid app to freemium model with in-app purchase

Question

I currently have a paid app in the store. Apple have not allowed a \'lite\' version to be submitted as well, so I have no choice but to update the current paid version to a

Answer 1

I've been thinking about this problem for some time now. I have a substantial amount of customers that paid for my (in App Store terms) high-price niche-App and I'd hate having to tell them to re-purchase as I plan to migrate to an In-App Purchase model.

The idea I came up with (and I'll ask Apple support whether it's legal) is to phase out the current paid App but ship a last update for it that allows "unlocking" the In-App purchases of the new App based on the In-App model. I was thinking about a challenge response scheme:

• User has installed paid App on his device
• User installs new In-App App and opens it. The new App detects the paid version and offers to unlock the In-App purchases (on this device only of course and as long as the App isn't deleted)
• The new App generates a nonce, signs it and calls the old App with it via an URL Scheme
• The old App decrypts the nonce, adds +1 one to it and signs it again. Calls back to the new App via URL scheme
• The new App validates the nonce and unlocks the features

The scheme can be easily implemented using a pre-shared key. It's of course a weakness on jail-broken devices, but then every App storing In-App receipts has those problems.