So I have been working on some ideas for securing cell phones from baseband level exploits and I was wondering if there are any potential complications with these solutions such as practicality or functionality.
First idea I had in mind was simply removing the Baseband OS from the processor itself or at least putting hardware level restrictions on what it is allowed to access. (Such as only allowing it to access the modems and phone antenna and such. Everything else would only be controlled by the application processor.)
The other idea was to place a Secure Cryptographic Module on the IO paths that transport data to and from application processor to the baseband. Or into the baseband processor itself. So that any and all data, voice, SMS, regardless of what cellular protocol is used be it 2G, 3G, 4G etc is enforced to be encrypted before it even leaves the device and is sent over the airwaves. This way there would be no way for an interceptor to be able to read anything that is captured regardless of how they exploit the device. There would of course be no way to turn this encryption off. It is always on.
The encryption would be done with a stream cipher that uses 256 bit keystreams and IVs.
So the question is, would there be any possible complications with implmenting these solutions that would interfere with the functionality or practicality of the phone?