FBI Director James Comey expressed alarm Wednesday about broadening use of encrypted communications, telling senators that investigators increasingly are unable to intercept or retrieve suspects’ messages.

Attempting to strike a humble tone, Comey praised what he says are benefits of encryption for privacy and cybersecurity and avoided making a direct request that Congress mandate “backdoor” access to communication devices and applications.

But Comey, a hero to some senators for opposing a Bush administration surveillance program, appeared to suggest there’s no valid need for strong encryption on smartphones.

“I don’t exactly know where the great demand for this is coming from,” he said, seeming to take a swipe at companies such as Apple, which recently unveiled default iPhone software making it impossible for the company to access phone content and much more difficult for police to do so.

“I haven’t met ordinary folks who say, ‘I really want a device that can’t be opened even if an American judge finds it ought to be opened,’” Comey said.

Sen. Mike Lee, R-Utah, suggested to Comey consumers are worried about someone without a warrant accessing their communications.

Comey and Deputy Attorney General Sally Yates told the Senate Judiciary Committee they’d like companies to retain user communications so they can be retrieved if a judge issues a warrant. End-to-end encrypted communication applications and smartphones that cannot be unlocked increasingly are hindering criminal and counterterrorism probes, they said.

Comey and Yates said the Islamic State group recruits would-be terrorists with public platforms like Twitter, then communicates over secure applications that cannot be monitored.

“We are stopping these things so far through tremendous hard work,” Comey said, “but I cannot see me stopping these indefinitely.” The FBI director said he didn't want to "scare people by saying I’m certain people will die” as a result, but it “sure does” increase that risk.

Earlier in the hearing, Comey assured senators there’s no possibility of unconstitutional mass surveillance should encryption safeguards be rolled back, an interesting assertion given whistleblower Edward Snowden's role popularizing encryption by exposing government mass surveillance programs.

“The Fourth Amendment prohibits, it’s against the law – folks will go to jail – if there are general warrants,” Comey said. “If law enforcement is reading everybody’s snapchats or everybody’s Instagram posts, you can’t do that.”

It’s unclear if Comey believes the reported large-scale collection of U.S. Internet communications and phone call records by intelligence agencies is blessed by de facto general warrants, as claimed in privacy lawsuits, or if the people who authorized and implement that collection belong in jail.

Manhattan District Attorney Cy Vance said he understands concern among experts and the public about reining in encryption, which critics say could open the door to hackers, too. But he said his office has experienced real-world difficulty unlocking phones.

“I understand there is a fear of mass security breaches, collection of bulk data and warrantless surveillance, and I believe those are valid and legitimate concerns,” Vance said, “but that is not the access local and state law enforcement seeks or expects. Our access to electronic data is grounded in and limited by the Fourth Amendment ... authorizing only reasonable searches based on probable cause, supported by a particularized search warrant and only after approval by a neutral judge.”

Technology experts later in the hearing said the government would need to launch a broad authoritarian crackdown on American Internet use and implement strict border controls to resolve concerns about encryption. Doing that would harm U.S. economic competitiveness, they said.

Georgia Institute of Technology law and ethics professor Peter Swire pushed back on claims authorities had fewer ways to track suspects than in the past.

“We are in a golden age of surveillance, not darkness,” Swire said, faulting the officials for failing to recognize a “cornucopia” of information that can be gleaned from metadata and location tracking, even if they can’t acquire message content.

“It takes nerve to say the glass is empty,” he said. “The bad guys could get encryption anyway … that would be true under any proposal.” Steps to roll back encryption standards would be “impractical, very very expensive and ineffective,” he concluded.

Hoover Institution research fellow Herbert Lin told senators blocking end-to-end communication apps would require a blanket ban on Americans downloading certain applications. “Then you'd have to start inspecting devices from overseas,” he said.

Experts and several senators noted that application developers need no corporate backing to create and distribute secure communication programs, which would remain true regardless of steps taken.