Despite early reports, experts agree that the leak of the iPhone Secure Enclave Processor firmware encryption key should not pose a security risk and
Despite early reports, experts agree that the leak of the iPhone Secure Enclave Processor firmware encryption key should not pose a security risk and may even ultimately improve user security.
When a hacker/researcher going by the handle “xerub” released the firmware encryption key, the initial reaction was one of panic because the iPhone Secure Enclave is responsible for storing and processing highly sensitive data, as described by Mike Ash, software engineer and fellow at Plausible Labs, in response to the debate around the FBI wanting backdoor access to Apple’s encryption:
“The Secure Enclave contains its own [unique ID] and hardware AES engine. The passcode verification process takes place here, separated from the rest of the system. The Secure Enclave also handles Touch ID fingerprint processing and matching, and authorizing payments for Apple Pay,” Ash wrote in a blog post about iPhone Secure Enclave last year. “The Secure Enclave performs all key management for encrypted files. File encryption applies to nearly all user data.”
While most iPhone system apps use Secure Enclave, and all third-party apps use it by default since iOS 7, Ash wrote, “The main CPU can’t read encrypted files on its own. It must request the file’s keys from the Secure Enclave, which in turn is unable to provide them without the user’s passcode.”
What Apple’s iPhone Secure Enclave leak means
While this sounds bad, David Schuetz, senior security consultant at NCC Group, said in his own analysis that the encryption key xerub released was specific to the GSM model of the iPhone 5S — the first Apple device with the Secure Enclave Processor — running iOS 10.3.3.
Apple reportedly told TechRepublic that decrypting the iPhone Secure Enclave firmware “in no way provides access” to user data and that Apple does not have plans to patch affected devices.
Xerub also told TechRepublic the encryption key would not impact user security but said the “public scrutiny” around the release could improve the security of the iPhone Secure Enclave.
Schuetz added that modifying the iPhone Secure Enclave firmware would not be possible because “the firmware is also signed by Apple, and the attacker would need to be able to forge the signature to get the phone to install the hacked firmware.”
“I think this is a good thing, in the long run. This should have very little practical effect on the security of individual iOS devices, unless a very significant flaw is uncovered. Even then, the potential scope of the finding may be limited to only older devices,” Schuetz wrote. “If the security of the Secure Enclave is in any way directly reduced by the disclosure of the firmware, then it wasn’t truly secure in the first place.”