A hacker going by the handle xerub has just released what he claims to be a full decryption key for Apple’s Secure Enclave Processor (SEP) firmware.
This could be a major blow for iOS security because of the importance of the SEP: It handles Touch ID transactions and is completely isolated from the rest of its host device. Your iPhone, iPad, or iPod has no idea what’s going on in the SEP, and that means no one else does either—at least until today.
Now that its firmware code is exposed it’s open season on SEP vulnerabilities.
What the Secure Enclave Processor is
Ever since Touch ID came out with the iPhone 5S, there has been a tiny coprocessor embedded in the main S-series, and now A-series, processor chip. That tiny coprocessor runs completely on its own—it has a separate OS, updates separately, and nothing it does is known to the rest of the device.
One of the key points of the SEP is its generation of the device’s Unique ID (UID). That UID is further secured by tangling it up with an ephemeral key that changes every time the device is rebooted.
Protecting the UID is why the SEP exists, and why all Touch ID actions, password verification, and other security processes happen inside it. .
Why the SEP’s decryption is a big deal
The SEP’s firmware code is now open to the world, thanks to xerub’s efforts. The key is published here, this GitHub repository contains what you need to decrypt it, and this one has the tools to process it.
“The fact that [the SEP] was hidden behind a key worries me,” said xerub. “Is Apple not confident enough to push SEP decrypted as they did with kernels past iOS 10?” He added that while SEP is amazing tech the fact that it’s a “black box” adds very little, if anything to security. “Obscurity helps security—I’m not denying that,” he said, but added that relying on it for security isn’t a good idea.
Expert hackers, he added, won’t be stopped by black boxes. Just slowed down.
“I think public scrutiny will add to the security of SEP in the long run,” xerub said, noting that was also his intention with releasing the key. It’s another act in the arms race between tech companies and hackers, who poke and prod software in a way that ultimately can make users safer.
“Apple’s job is to make [SEP] as secure as possible,” xerub said. “It’s a continuous process … there’s no actual point at which you can say ‘right now it’s 100% secure.'”
Decrypting the SEP’s firmware is huge for both security analysts and hackers. It could be possible, though xerub says it’s very hard, to watch the SEP do its work and reverse engineer its process, gain access to passwords and fingerprint data, and go even further toward rendering any security relying on the SEP completely ineffective.
“Decrypting the firmware itself does not equate to decrypting user data,” xerub said. There’s a lot of additional work that would need to go into exploiting decrypted firmware—in short it’s probably not going to have a massive impact.
An Apple spokesperson, who wished to remain unidentified, stated that the release of the SEP key doesn’t directly compromise customer data. “There are a lot of layers of security involved in the SEP, and access to firmware in no way provides access to data protection class information.”
The Apple source added that it’s “not an easy leap to say it would make getting at customer data possible.” Rather, it makes research into the structure of the SEP possible. It’s there that hackers could find flaws that allow them to continue digging deeper.
Apple does not plan to roll out a fix at this time.
There’s no telling when any potential effects of the SEP’s decryption could start being felt, or in what way. Ideally, Apple will release a fix as soon as possible, but failing that be on the lookout for Touch ID hacks, password harvesting scams, or other attacks that could take advantage of the decryption.