Inside the FBI's encryption battle with Apple

For months, the FBI searched for a compelling case that would force Apple to weaken iPhone security - and then the San Bernardino shooting happened

Two weeks ago, the Federal Bureau of Investigation called Apple's headquarters in Cupertino, California, with a jarring message: the agency wanted Apple to help them hack an iPhone. Apple refused.

The request stepped up a level on 16 February when a federal magistrate ordered Apple to help the FBI unlock a single iPhone - the phone belonging to one of the killers in the December mass shooting in San Bernardino, California. Apple again refused.