FBI director says iPhone unlock demands are limited, won't 'set a master key loose'

"The particular legal issue is actually quite narrow," Comey wrote in Lawfare. "The relief we seek is limited and its value increasingly obsolete because the technology continues to evolve."

The FBI has been asking that Apple modify iOS 9 on a single iPhone to remove a limit on passcode attempts. When on, the feature prevents hackers from trying a brute-force unlock, since iOS will automatically delete a device's data after the limit is reached.

"We simply want the chance, with a search warrant, to try to guess the terrorist's passcode without the phone essentially self-destructing and without it taking a decade to guess correctly. That's it. We don't want to break anyone's encryption or set a master key loose on the land," Comey added.

The comment is a direct reference to Apple CEO Tim Cook's argument that creating a workaround for the FBI would also create a "master key" that could be used to break into any iPhone, not just Farook's, and undermine the security of all iOS devices.

Comey suggested that there is now a "serious tension" between privacy and security created by new technology, which should be resolved not by corporations or the FBI but by the American public, which also needs to find the "right balance" given the long-term impact. He also invoked the memory of the San Bernardino victims however, saying that the FBI "simply must do all we can under the law" to investigate.

On Monday Cook issued a memo to Apple workers, calling on the FBI to withdraw its demands. He also supported the idea of a government commission or panel to address the issue of encryption.

Recently it was revealed that the FBI worked with San Bernardino County to reset the Apple ID password associated with Farook's iPhone, ironically preventing Apple from retrieving data via an iCloud backup.