[acqq]

Apparently, devices with A6 processors, such as the iPhone 5C contain a hardware key that is somehow "unreachable" and "unique" but it is "tangled" with the phone passcode to create the encryption key with which the rest of the data is encrypted. It's less than the whole "enclave" but there is the hardware dependency.

I haven't seen anybody presenting enough details about this implementation to estimate what would be the easiest attack vector, but I guess once it's not limited to "which software I can run" but assuming "we can control the hardware environment of the CPU too" there's more that can be done in this case.