The F.B.I. director and the Manhattan district attorney on Wednesday sought to reopen the argument that law enforcement and intelligence officials need to have access to encrypted information on smartphones with court approval.

The question seemed settled last month after President Obama decided not to push legislation requiring American technology companies — notably Apple, Google and Facebook— to roll back smartphone encryption schemes that make it almost impossible to read a target’s communications, even if investigators have a court order. But the terrorist attacks in Paris may have changed the politics on both encryption and a range of surveillance issues, with critics renewing their charge that the Obama administration is not using all tools available to stop terrorism.

In a speech at a cybersecurity conference in New York, James B. Comey, who since taking over the F.B.I. has been the most vociferous about the “going dark” problem facing investigators, warned that “we’re drifting to a place” where court orders to gain access to text messages or computer communications “are ineffective.” Both devices and data in transmission are often encrypted so well that the law enforcement and intelligence agencies cannot crack the coding — and their makers have designed the system so they do not hold the key.

“With lack of cooperation, we are left with 50-foot-high walls on either side,” Mr. Comey said. “We have to get to a place where we push information to each other at a pace that moves with the speed of the threat.”