Apple tells US judge iPhones are 'impossible' to unlock

Apple says it's only possible to decrypt iPhone data if you know the encryption key

Apple has said that encrypted data on newer iPhones can't be accessed, even by Apple, though the firm could in theory help police unlock older phones.

The comments came in a briefing filed on Monday to a US judge who asked for Apple's input in a case.

A US Department of Justice request has tried to force the company to help prosecutors access a seized iPhone.

According to Apple, 90% of its devices running iOS 8 or higher can't be unlocked.

The phone that is the subject of the justice department's request is an older device, but Apple has so far resisted unlocking it for authorities.

"Forcing Apple to extract data in this case, absent clear legal authority to do so, could threaten the trust between Apple and its customers and substantially tarnish the Apple brand," the company said in its briefing.

US magistrate Judge James Orenstein, of Brooklyn in New York, has scheduled a hearing for Thursday though it is not clear whether an Apple representative will be present.

In order to decrypt the data on newer devices, the encryption key - known only to the user - would have to be entered.

'No back doors'

Meanwhile, Apple chief executive Tim Cook has told an audience in California that the company does not allow intelligence agencies to access data via "back doors" in its software.

"We think encryption is a must in today's world," said Mr Cook, speaking at the Wall Street Journal's WSJDLive conference.

"No-one should have to decide privacy or security. We should be smart enough to do both."

Apple boss Tim Cook has said there are "no back doors" in Apple software

The data encrypting services that come with the latest smartphone and computer operating systems can only be unlocked when a specific key is used, according to Dr Joss Wright of the Oxford Internet Institute.

"Apple may supply the device and system but if they don't have that key they're not able to unlock it any more than the US state department," he told the BBC.

He added that law enforcement agencies often found themselves attempting to circumvent this problem.

'Unbreakable'

This can be done by getting the user to voluntarily give up the key or by installing malware on the user's phone that snoops on the key as it is typed in.

"The core encryption is as near to unbreakable as you can get," he said.

"The point is you don't try to break the encryption, you break the software - you try to get the password from the user's computer so you can unlock it."

In another privacy-conscious step, Apple also recently removed more than 250 apps from the app store which used Chinese advertising software to extract personally identifiable information about users.

According to the company, this information included email addresses and data that could identify individual devices.

Apple said it would work with developers to get updated versions of their apps back on the app store "quickly".