Explaining Apple’s Fight With the FBI

Tuesday evening, a federal court ordered Apple to help the FBI unlock an iPhone used by one of the attackers who killed 14 people in San Bernardino, Calif., in December.

Wednesday morning, Apple said in a strongly worded letter that it would challenge the court’s request. While technology companies recently have resisted government demands, Apple’s letter is one of the industry’s most forceful pushbacks against a court ruling.

In the hours after Apple’s letter was published, technologists and legal experts have been dissecting what, exactly, the Cupertino, Calif., company can’t — or won’t — do to help the government.

What is the government asking for?

The Federal Bureau of Investigation wants to examine the iPhone used by Syed Farook to determine whether he and his wife, Tashfeen Malik, had planned the shooting directly with the Islamic State. The iPhone, a 5c version of the smartphone that was released in 2013, is locked by a passcode, which the F.B.I. wants Apple to circumvent.Apple would have to build a new version of its iOS smartphone software that allows the F.B.I. to bypass certain restrictions. Apple claims this software can give someone “the potential to unlock any iPhone in someone’s physical possession.”

So what does the court order require Apple to do?

The court is ordering the company to “bypass or disable” a feature that automatically wipes an iPhone clean of all its data after 10 incorrect password attempts have been entered. This is a standard feature on iPhones.

Technically, that would not require Apple to decrypt the passcode that blocks access by outsiders to the iPhone. It would allow the government to try an unlimited number of passwords without fear of the phone erasing all of its stored information.

In electronic security parlance, that is what is called a “brute force” attack, and all it takes is time and patience to submit a large number of passcodes. Brute force attacks are usually carried out with the assistance of a powerful computer, which can automatically input millions of different password combinations until it guesses the correct one.