The encryption used by the iPhone to protect its storage*is a multi-tiered system. At its core are two keys, one embedded in the hardware and the second derived from the PIN. The hardware key is used to generate a file system key that is in turn used to encrypt the file system metadata. That metadata includes an encryption key for each individual file. That per-file key is encrypted using (indirectly) an encryption key that is derived from a combination of the hardware key and the PIN key. As such, without the PIN key, it's impossible to decrypt those per-file keys and hence impossible to decrypt files stored on the iPhone.
http://arstechnica.com/apple/2016/02...e-desired-key/
http://arstechnica.com/apple/2016/02...e-desired-key/
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