The security coprocessor was introduced alongside the iPhone 5s and Touch ID. It performs secure services for the rest of the SOC and prevents the main processor from getting direct access to sensitive data. It runs its own operating system (SEPOS) which includes a kernel, drivers, services, and applications.
The Secure Enclave is responsible for processing fingerprint data from the Touch ID sensor, determining if there is a match against registered fingerprints, and then enabling access or purchases on behalf of the user. Communication between the processor and the Touch ID sensor takes place over a serial peripheral interface bus. The processor forwards the data to the Secure Enclave but can’t read it. It’s encrypted and authenticated with a session key that is negotiated using the device’s shared key that is provisioned for the Touch ID sensor and the Secure Enclave. The session key exchange uses AES key wrapping with both sides providing a random key that establishes the session key and uses AES-CCM transport encryption
Today, xerub announced the decryption key 'is fully grown'. You can use img4lib to decrypt the firmware and xerub's SEP firmware split tool to process.
Decryption of the SEP Firmware will make it easier for hackers and security researchers to comb through the SEP for vulnerabilities.
You can find the decryption key at the link below. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.
Read More [via @xerub]