Re: The Power of the SCOTUS VIII - I am certiorari we'll be arguing until Thanksgivin
I don't know 100% of the technical details, but this is an iPhone 5C, so it is lacking some specialized security hardware (called the Secure Enclave by Apple) so hacking it is more feasible than an iPhone 5S, 6, etc. I believe the 5C uses 256-bit AES encryption, which is considered unbreakable by the NSA and is approved by the NSA for top secret data. The data stored on the device is encrypted by a 256-bit key that is randomly generated by the phone when the device is setup. Apple doesn't know the key, and a 256-bit key is impossible to brute force. Of course you don't type a 256-bit key to unlock your phone. That key is stored on the iPhone and is encrypted by another key. That key, on an iPhone 5C, is likely generated from the user's passcode and a hardware specific unique ID. When the phone is locked, it 'forgets' this key used to unlock the 256-bit encryption key. It needs to be regenerated to unlock the phone. The passcode is unknown to Apple, and the UID can only be obtained from the phone hardware (this last bit means that the unlock attempt needs to run on the phone itself, unless you have some way to extract the UID from the device, which might be more possible on a 5C).
Anyway, brute force cracking a 6-8 character user generated passcode isn't computationally difficult. The problem is the passcode must be entered on the touchscreen (so not via bluetooth), there is a 80ms delay between attempts to unlock, and the phone can be set to erase itself after 10 incorrect attempts (it could just delete the 256-bit encryption key, which is as good as erasing the data). The FBI wants a way around these limitations so they can go after the weak-link in encryption - the passcode.
It is possible to load signed software via USB and run it on the iPhone. This is what the FBI wants from Apple - a special iOS that does not have the above limitations and will let them brute force crack the user passcode. The software would be loaded into the phone's RAM and executed via a special USB mode, so the data on the phone is not altered.
Apple doesn't want to be in the business of hacking devices that they marketed as secure. Also, what if next time it is a iPhone 6, or some newer iPhone with more advanced security features? Will they need to add a back door to assist with future FBI requests on future 'unbreakable' iPhones? That inherently makes the device less secure, and any back door will eventually be exploited.