"I'd be surprised if more than a handful of members would support the idea of backdooring Americans' personal property," Sen. Ron Wyden, an Oregon Democrat and vocal privacy advocate, said.
An aide to Senate Judiciary Committee Chairman Patrick Leahy said the senator is open to reviewing the FBI's proposal, but that right now, he's focused on passing his own bill that would rein in government spying.
And a House Democratic aide said that staffers have been in touch with the FBI on the issue but that Congress is unlikely to force technology companies to build backdoors into their networks and devices anytime soon.
"I think the combination of business and civil-liberty concerns would have made this proposal difficult to adopt even before the Snowden disclosures," the aide said. "In the middle of a surveillance-reform fight, it's just that much more complicated."
The FBI director warned Thursday that encryption technologies are allowing criminals to become "beyond the law." Even with a court order, police are unable to access information that is critical to solving crimes, he said.
"The FBI has a sworn duty to keep every American safe from crime and terrorism, and technology has become the tool of choice for some very dangerous people," Comey said in a speech at Brookings. "Unfortunately, the law hasn't kept pace with technology, and this disconnect has created a significant public-safety problem."
The Communications Assistance for Law Enforcement Act, a 1994 law known as CALEA, forces telephone companies to build surveillance technologies into their networks to allow law enforcement to install wiretaps. But the law hasn't been updated and doesn't cover new devices and online forms of communication.
Apple and Google recently announced that their new phones will feature default encryption that will make it impossible to unlock the devices for police. "Are we so mistrustful of government—and of law enforcement—that we are willing to let bad guys walk away ... willing to leave victims in search of justice?" Comey asked.
He urged Congress to update CALEA to "create a level playing field" so that companies like Google and Apple have to provide police the same access to information that telephone providers like AT&T do.
But the plan will face fierce resistance from tech companies and privacy advocates. They warn that any backdoor for law enforcement could also be exploited by hackers. Greg Nojeim, a senior counsel with the Center for Democracy and Technology, said he doubts Congress will enact legislation to make U.S. products less secure.
"Who in Europe is going to buy these newly compromised cell phones if Congress insists that they be made with backdoors for U.S. law enforcement?" Nojeim asked. "It's probably one of the worst job killers a member of Congress could propose."