Privately sharing data between iOS apps that have different team IDs

Question

How can I privately share data between two apps on the same device that have different team IDs? We used to do this via the pasteboard, but with iOS7 to use app-specific pasteboards they now have to have the same team id.

The problem we are trying to solve is the unlocking of features in one app if the user has purchased another app. We'd like this to happen quietly in the background (hence originally using app-specific pasteboards) but having some security to prevent users from spoofing the process and unlocking features.

One approach we are investigating is to use a system pasteboard but to encrypt the data with a device specific key. As long as both apps use the same algorithm to generate the key this should work, but he problem then becomes how to generate an app specific key.

Any advice/guidance on the best way of enabling this sort of feature unlocking scheme would be very helpful.

Answer 1

I use the pasteboard for sending data between applications as well. It's a really useful tool for sending medium size amounts of data between applications. I actually wrote up a blog post on the topic a while back.

Unfortunately, as you've pointed out, private pasteboards are only available to apps that share the same prefix in their app id. This is typically the Team ID, but may be different if you have an app that dates back to when you could use a different bundle seed identifier.

If you have medium sized amounts of private data being shared between apps with different prefixes then a different solution is in order. In this case I would suggest using some form of encryption and using the general pasteboard to shuttle the data around. Depending on the sensitivity of the data, it probably would be a good idea to encrypt the data even when using a private pasteboard. Rob Napier has a nice library for making the encryption and decryption very simple.

Alternatively, if your data is fairly small you might consider encoding the data into a URL and using a URL scheme to move the data into the other app.