-- The head of the FBI today dismissed concerns that forcing Apple to hack into an iPhone left behind by one of the San Bernardino shooters could ultimately allow access to others' phones around the world.
"The code the judge has directed Apple to write works only on this one phone, and so the idea of it getting out in the wild and it working on my phone or your phone ... is not a real thing," FBI Director James Comey told the House Intelligence Committee. "The second thing is that the code will be at Apple, which I think has done a pretty darn good job of protecting its code."
Comey noted that before 2014, Apple was able to unlock any phone manufactured by the company, "and I don’t remember any code getting out that let that ability loose upon the land."
Nevertheless, Comey called the issue at the heart of a growing dispute between the FBI and Apple "the hardest question I’ve seen in government."
Syed Farook and his wife, Tashfeen Malik, launched a deadly assault on Dec. 2, 2015, killing 14 of Farook's coworkers at a holiday party in San Bernardino, California. With attacks like that, the public needs to understand "the costs associated with moving to a world of universal, strong encryption," Comey said.
"I love encryption," Comey insisted, but law enforcement "really does save people’s lives, rescue kids [and] rescue neighborhoods from terrorists ... and we do it a whole lot through search warrants of mobile devices."
He said there are "increasing situations where we cannot with lawful court orders read the communications of terrorists, gang-bangers, pedophiles, all different kinds of bad people." So, he said, "if we’re going to move to a world where that is not possible anymore, the world will not end, but it’ll be a different world than where we are today."
Testifying beside Comey today, NSA Deputy Director Rick Ledgett emphasized the importance of gaining access to the contents of communications, not just so-called "metadata" showing a phone user's location or who that user has called.
"It’s one thing to know that a person is in a particular place at a particular time," Ledgett said. "It’s something else entirely -- and necessary to understanding and defeating terrorist plots -- to know what the target is, what the timing is, how the attack is going to develop."
At the hearing today, Comey also dismissed suggestions that the FBI has the technical means to access Farook's phone but isn't doing it. Comey called such suggestions "the product of people watching too many TV shows."
Last week, at the Justice Department's request, U.S. Magistrate Judge Sheri Pym in California ordered Apple to help the FBI crack open Farook's iPhone.
Federal prosecutors say the phone, given to Farook by his employer, could be hiding "crucial evidence" about the terror attacks.
"The government requires Apple's assistance to access the ... device to determine, among other things, who Farook and Malik may have communicated with to plan and carry out the IRC shootings, where Farook and Malik may have traveled to and from before and after the incident, and other pertinent information that would provide more information about their and others' involvement in the deadly shooting," prosecutors said in their initial filing on Tuesday, Feb. 16.
Prosecutors said Farook's device could be encrypted to the point that its content would be "permanently inaccessible," and that "Apple has the exclusive technical means which would assist the government in completing its search."
"Apple’s current refusal to comply with the Court’s Order, despite the technical feasibility of doing so, instead appears to be based on its concern for its business model and public brand marketing strategy," the government filing said.
After Pym issued her order on Feb. 16 demanding that Apple assist federal agents, Apple quickly vowed to challenge the decision.
"The FBI wants us to make a new version of the iPhone operating system, circumventing several important security features, and install it on [the shooter's] iPhone," Cook added. "In the wrong hands, this software -- which does not exist today -- would have the potential to unlock any iPhone in someone’s physical possession."
In addition, all of the personal and sensitive information on customers' phones "needs to be protected from hackers and criminals who want to access it, steal it, and use it without our knowledge or permission," Cook wrote.
If the battle between the FBI and Apple continues, it's a matter that could work its way up to the U.S. Supreme Court.
ABC News' Kelly Stevenson and Julia Jacobo contributed to this report.