Facebook has shot down a request from US Attorney General William Barr to open up the company's end-to-end encryption effort to law enforcement.
In October, Barr, and his counterparts in the UK and Australia, called on Facebook to halt a plan to expand encryption across the company's messaging products. In response, Facebook has formally rejected the request with a letter the company is now making public.
"The 'backdoor' access you are demanding for law enforcement would be a gift to criminals, hackers, and repressive regimes," WhatsApp and Facebook Messenger executives wrote in the Monday letter.
Encryption can prevent a provider, like Facebook, from reading your private messages in plain text. However, federal investigators argue the same privacy-enhancing technologies can help criminals and terrorists mask their activities, and stop law enforcement from accessing their devices.
In their October request, Barr and his counterparts emphasized how sex offenders can use encryption to help them prey on underage users. "It is critical to get this right for the future of the internet," they wrote at the time. "Children's safety and law enforcement's ability to bring criminals to justice must not be the ultimate cost of Facebook taking forward these (encryption) proposals."
Ideally, only government agents with a warrant would be able to access any backdoor and decrypt private messages. But in Monday's letter, Facebook rejected the idea as dangerous.
"It is simply impossible to create such a backdoor for one purpose and not expect others to try and open it," the company's executives wrote. "People's private messages would be less secure and the real winners would be anyone seeking to take advantage of that weakened security. That is not something we are prepared to do."
It's the same argument Apple made when the FBI sought a backdoor into iOS in order to access an iPhone belonging to one of the San Bernardino shooters. Ultimately, the agency hired an outside firm to crack the smartphone.
So far, the Justice Department hasn't responded to Facebook's letter. But the encryption debate isn't going away anytime soon. On Tuesday, the Senate Judiciary Committee held a hearing on the same topic, where the District Attorney of New York County, Cyrus Vance, called on Congress to intervene and create legislation to enable the backdoor access.
"Allowing private companies in Silicon Valley to continue to assert themselves as the unregulated gatekeepers of critical evidence is dangerous, and warrants legislative intervention," he said.
In the meantime, Facebook says it's still eager to work with law enforcement on stopping criminals on the company's products. This includes the company responding to valid legal requests, like a warrant, for information on a user.