All Apple devices are AES encrypted with a combination of a key on flash in the CPU, and a unique static key in the CPU core. "Erasing" the phone just removes t

All Apple devices are AES encrypted with a combination of a key on flash in the CPU, and a unique static key in the CPU core. "Erasing" the phone just removes the key, rendering the bulk flash storage completely useless. There's never any data stored which is not encrypted.