I have developed an app for Android/iOS which calculates a value based on the users input. If an event occurs, this calculated value will be sent to my Backend as normal HTTPS payload. My question is now, how can I make sure, that this value is really only calculated by the source code of my app? Is there a way to handle such a problem?
To make it clear: I want to avoid, that somebody is rooting his phone, extract the Auth-Token from the private storage of my app and sends a valid HTTPS-Payload to my Backend with fictitious payload, manually or by manipulating the source code.
From the view of the backend, it's difficult to evaluate the payload based on its values if it is valid or not.
Any suggestions appreciated!
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For the sake of completeness: apart from the answers here, the following are also very interesting:
Where to keep static information securely in Android app?
How to secure an API REST for mobile app? (if sniffing requests gives you the "key")