Securing form data from modification on phone

Hi,

ODK Collect app stores the submitted form data in the phone or SD card memory in the form of XML files. This data is editable if opened with any file editor on the phone in ODK folder, which opens up the possibility of changing the data unauthorized. I am looking for a feature which could safeguard this data from editing outside the app.

This feature is different from the ENCRYPTED FORM technique mentioned on the ODK website. In that technique, the data is encrypted fine, but its decryption is done with ODK briefcase only. This means that the data is not viewable either at the aggregate level or some customized dashboard connected to Aggregate. It also makes ODK briefcase a compulsory tool, which normally is not used in online server situations.

Inviting fruitful discussion and more use cases of this and up-voting please...

Thanks!
Saad Omer