Explained: The US Justice Department’s new quarrel with Apple

The deadly shooting of three US sailors at a Navy installation in December could reignite a long-simmering fight between the federal government and tech companies over data privacy and encryption.

As part of its probe into the violent incident, deemed a terrorist act by the government, the Justice Department insists that investigators need access to data from two locked and encrypted iPhones that belonged to the alleged gunman, a Saudi aviation student. The problem: Apple designed those iPhones with encryption technology so secure that the company itself can’t read private messages.