FBI Director Says iPhone Unlocking Method Can't Crack New Models

"It's a bit of a technological corner case, because the world has moved on to 6's," FBI Director James Comey says. Kevin Lamarque/Reuters

Is the fight between Apple and the FBI back on? Following a détente after the FBI found a method to unlock the iPhone 5c of one of the San Bernardino, California, shooters, FBI Director James Comey admitted the method will not work for iPhone models that came after the 5c.

At a talk in Kenyon College in Gambier, Ohio, Comey said the undisclosed unlocking method works only for a "narrow slice of phones," not including the new iPhone 6 or 6s. "It's a bit of a technological corner case, because the world has moved on to 6's," Comey says. "This doesn't work on 6's, doesn't work on a 5s."

(The quote starts around the 52:30 mark.)

The most likely reason why the FBI can't crack open newer iPhones is a central processing unit chip called the Secure Enclave. First installed inside an iPhone 5s, Secure Enclave handles the most sensitive data of the iPhone, such as Apple Pay and Touch ID, and encrypts data on the phone, including Messages, according to Vice Motherboard.

"The Secure Enclave adds an additional line of defense against attacks by implementing core security and cryptography features in a separate CPU within Apple's hardware," wrote cybersecurity expert Mike Ash. "The iPhone 5c that the FBI is asking Apple to break into predates the Secure Enclave, and so can be subverted by installing a new OS signed by Apple that removes the artificial passcode delays."

Comey added that the FBI hadn't told Apple yet about its new method out of fear that the company might patch up the vulnerability and bring the FBI "back where we started from." But he added that the FBI might share the information in the near future. He also said he had "a high degree of confidence" in the unnamed company that sold the FBI the method to keep it under lock.

In the keynote speech before the Q&A talk, Comey reiterated his support for strong encryption but warned about the cost of having one so absolute and impenetrable—in line with what President Barack Obama said at the SXSW Conference in March.

"I love strong encryption. It protects us in so many ways from bad people," Comey. "But it takes us to a place—absolute privacy—that we have not been to before where the balance we have long struck is fundamentally challenged and changed. That is why we need to have an adult conversation about the balance that means so much to all of us."