After my brief read, one of the main reasons they’re using PCC to produce the signed JPEGs, instead of doing everything on device, is that it maintains your privacy.
If you were signing with the iPhone, an attacker could then correlate photos taken with the same device.
Apple certainly has the data that “this sensor, in this device, took this exact photo” in PCC at the time of signing, but they discard that data.
After my brief read, one of the main reasons they’re using PCC to produce the signed JPEGs, instead of doing everything on device, is that it maintains your privacy.
If you were signing with the iPhone, an attacker could then correlate photos taken with the same device.
Apple certainly has the data that “this sensor, in this device, took this exact photo” in PCC at the time of signing, but they discard that data.