A United States judge ordered Apple on Tuesday to cooperate with the Federal Bureau of Investigation to unlock the iPhone of one of the San Bernardino shooters and access data 

A cryptography expert, however, has estimated that it could take 10 years to break the password on the gunman's phone.

NBC News reports that a federal judge mandated Apple to help investigators gain access to the encrypted data on the iPhone 5c used by Syed Farook, one of the shooters behind the deadly attacks in San Bernardino, California in December 2015. Farook and his wife Tashfeen Malik are responsible for killing 14 people on Dec. 2.

This order comes hot on the heels of FBI Director James B. Comey's admission a few days ago that the bureau has not been able to open one of the phones of the murderers.

“It has been two months now, and we are still working on it,” Comey told Congress a week ago.

Relevant, Critical Data

In its 40-page filing, the United States Attorney's Office in Los Angeles says it needs Apple's help to crack the password of Farook's iPhone to obtain "relevant, critical ... data" that will help authorities understand the truth behind the attack. 

The data may help in finding out who the assassins were communicating with to help them plan and execute the attack. It may also provide information as to where the attackers traveled before the shooting. 

"Despite … a warrant authorizing the search, the government has been unable to complete the search because it cannot access the iPhone's encrypted content," prosecutors say.

They believe Apple has the exclusive technical means to help the government carry out its investigation, "but has declined to provide that assistance voluntarily." 

United States Attorney Eileen M. Decker says in a statement that this move is a "potentially important step" in learning everything about the San Bernardino attack.

The Ruling

The judge ordered Apple to provide "reasonable technical assistance" to the FBI to salvage the data from Farook's iPhone. This includes disabling the device's auto-erase function and allowing investigators to submit an unlimited number of passwords to unlock the device. 

Apple has five days to respond to the court if it thinks that conforming to the order would be "unreasonably burdensome." 

The Complication

There's an obstacle, though. The process of cracking an iPhone's password can take a long time. Apple says it would take 5 1/2 years to guess a six-digit password using lowercase letters and numbers. 

Using a supercomputer can significantly hasten the process, but the FBI still needs to obtain the hardware key built into the iPhone. Apple doesn't keep a copy of the key, and the FBI can only access it by resorting to a multitude of techniques that do not guarantee they will be able to recover the passcode. 

Matthew Green, a cryptography expert at Johns Hopkins University, says the FBI could crack a six-digit numeric code in around 22 hours.

"But once there's numbers and letters, that's when things get interesting." Green tells The Washington Post.

He says it may take 10 years for the investigators to crack a strong password on the phone. That means it could take until 2026 before the case is closed.