FBI says iPhone unlocking method won't work with newer models

The Federal Bureau of Investigation'ssecret method for unlocking the iPhone 5c used by one of the SanBernardino shooters will not work on newer models, FBI DirectorJames Comey said.

"We have a tool that works on a narrow slice of phones,"Comey said at a conference on encryption and surveillance at
Kenyon University in Ohio late on Wednesday.

Apple's shares were down 1.3 per cent at midday.

Comey added that the technique would not work on the iPhone5s and the later models iPhone 6 and 6s. The iPhone 5c model wasintroduced in 2013 and has since been discontinued by Apple asnewer models have become available.

The Justice Department said in March it had unlocked the SanBernardino shooter's iPhone with the help of an unidentifiedthird party and dropped its case against Apple Inc,ending a high-stakes legal clash but leaving the broader fightover encryption unresolved.

Apple's help may be needed in other cases

As the technique cannot be used to break into newer models,law enforcement authorities will likely have to lean on Apple tohelp them access the devices involved in other cases.

The Justice Department has asked a New York court to forceApple to unlock an iPhone 5s related to a drug investigation.

Prosecutors in that case said they would update the court byApril 11 on whether it would "modify" its request for Apple'sassistance.

If the government continues to pursue that case, thetechnology company could potentially use legal discovery to
force the FBI to reveal what technique it used, a sourcefamiliar with the situation told Reuters.

Apple and the FBI were not immediately available forcomment.

The FBI began briefing select U.S. senators this week aboutthe method used to unlock the San Bernardino iPhone.

Up to Wednesday's close of $110.96 US, Apple's shares had risenmore than 5 per cent this year.