Kevin Johnson

USA TODAY

FBI Director James Comey said that the new tool used to successfully hack into the iPhone of San Bernardino terrorist Syed Farook will not work on newer model Apple Inc., devices, suggesting that the application of the undisclosed method to resolve hundreds of pending cases involving locked devices now held by federal and state authorities will likely be limited.

In a speech at Kenyon College, Comey said the method, provided by an undisclosed outside party, only unlocked an iPhone 5c, which was used by Farook as an employee of San Bernardino County.

"The world has moved on to 6's,'' Comey said of the newer model phones. "This doesn't work in 6s; this doesn't work in a 5s... We have a tool that works on a narrow slice of phones.''

Comey continued to decline to identify the entity that provided the tool, but believed the method would be "closely protected'' and would be used "lawfully and appropriately.''

Hundreds of requests to unlock phones flood FBI

"The FBI is very good at keeping secrets,'' he said, adding that the government has yet to decide whether to share the tool with Apple.

"We may end up there,'' he said. "We just haven't decided yet.''

Last week, the FBI abruptly withdrew from its legal battle to force Apple's assistance in unlocking the Farook phone after getting the help of the outside party. At the time, Apple was resisting a federal magistrate's order directing the tech giant to help.

FBI hacks into terrorist’s iPhone without Apple

Comey defended the legal action, saying that it "really, really was about getting access to a terrorist's phone.''

"It was not about setting precedent,'' he said, though he believed the courts were not the best venue to resolve the broad issues related to encryption. "It is a good thing the litigation is over,'' Comey said. "But it would be a bad thing if the conversation was over.

"At some point (encryption) is going to figure in a major tragedy,'' the FBI director added.

The high-profile legal fight between the FBI and Apple turned a spotlight on the similar plight of state and local law enforcement agencies who are holding hundreds of devices seized as part of criminal investigations but whose contents are not accessible to investigators.

Last week, a survey of more than a dozen local law enforcement agencies, based on data gathered by the Manhattan District Attorney's Office and USA TODAY, found that investigators have been blocked from the contents of more than 1,000 smartphones and other devices in recent months.

The FBI also has recently disclosed that at the same time that it was struggling to unlock the Farook phone, the agency was being inundated with requests from local agencies seeking help accessing the contents of hundreds of encrypted or damaged devices linked to unrelated criminal investigations across the country.