The Justice Department argued Thursday that compelling Apple to help unlock an iPhone in California is a modest demand which may turn up evidence of a terrorist attack.
The government's response was the latest in the legal battle which has stirred an intense debate on whether Apple must comply with a court order to help the FBI break into a phone used by one of the shooters in the December terror attacks in San Bernardino, California.
The brief filed in federal court came in response to a challenge by Apple, backed by a broad coalition of technology firms and activists, which said the FBI was seeking a "back door" into all iPhones as part of the probe.
The government brief, in sharp contrast, claimed it is a single case of technical assistance in an important national security investigation.
"The court's order is modest. It applies to a single iPhone, and it allows Apple to decide the least burdensome means of complying," the Justice Department lawyers wrote.
"As Apple well knows, the order does not compel it to unlock other iPhones or to give the government a universal 'master key' or 'back door.' It is a narrow, targeted order... The government and the community need to know what is on the terrorist's phone, and the government needs Apple's assistance to find out."
The government brief said there is ample legal precedent for the request, saying it is similar to requiring telephone companies to install wiretaps under court orders.
Government lawyers wrote that Apple is "fully capable of complying with the court's order" and has stated that it would need "as few as six of its 100,000 employees for perhaps as little as two weeks."
A 'marketing decision'
The brief repeated the argument -- hotly contested by Apple -- that the iPhone maker took a "deliberate marketing decision to engineer its products so that the government cannot search them, even with a warrant."
It said Apple and its backers "try to alarm this court with issues of network security, encryption, back doors, and privacy," and called this "a diversion."
"Apple desperately wants -- desperately needs -- this case not to be about one isolated iPhone,'" the Justice Department said.
"But there is probable cause to believe there is evidence of a terrorist attack on that phone, and our legal system gives this court the authority to see that it can be searched pursuant to a lawful warrant."
The brief said Apple is seeking to rally public support with "rhetoric (that) is not only false, but also corrosive of the very institutions that are best able to safeguard our liberty and our rights."
In a supporting statement, the government filed an affidavit from FBI engineer Stacey Perino, disputing Apple's claim that software the FBI wants it to create -- which would disable the iPhone mechanism to destroy data with repeated passwords attempts -- could be used on other devices.
"Because an iPhone requires Apple to have cryptographically 'signed' code before an iPhone will run it, and changing a unique device identifier within the (software) would invalidate Apple's signature, the (software) would not run on other iPhones," Perino stated.
The brief also raised the possibility the government would demand Apple's closely guarded software secrets -- its source code and private electronic signature -- if the company refuses to cooperate.
"The government did not seek to compel Apple to turn those over because it believed such a request would be less palatable to Apple," the brief said.
"If Apple would prefer that course, however, that may provide an alternative that requires less labor by Apple programmers."
A judge is scheduled to hear oral arguments on March 22 in the case, which has sparked a debate around the globe, even from the top UN human rights official, who argued that forcing Apple to help could weaken overall security for activists around the world.
Apple's chief Tim Cook claimed the order would force Apple to "hack" its own devices and compromise security for all Apple devices.
Others have argued that weakening the iPhone security would create software that would leak out to malicious actors, and that Apple and other technology firms would be "conscripted" to spy on its customers.