Writing an API for an iPad app for other apps to use - is this possible?

I am hoping to create an iPad app to do the following:

Download data from a user's machine/local server Encrypt this data and store it securely on the iPad Provide an API so that others can write specially signed apps that query this API to access the secure data.

Its is the last requirement I am starting to think is "impossible". Does anybody know w开发者_高级运维hether it is possible or not and if not of any solutions?

Thanks

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If you want to share data between applications, a good solution is to create a custom clipoard type, and have both applications access it.

You can also write your data in a file, and ask iOS to open that file in another application. This other application will then open and decrypt the contents of this file.