SAN FRANCISCO — An elite group of security technologists has concluded that the American and British governments cannot demand special access to encrypted communications without putting the world’s most confidential data and critical infrastructure in danger.

A new paper from the group, made up of 14 of the world’s pre-eminent cryptographers and computer scientists, is a formidable salvo in a skirmish between intelligence and law enforcement leaders, and technologists and privacy advocates. After Edward J. Snowden’s revelations — with security breaches and awareness of nation-state surveillance at a record high and data moving online at breakneck speeds — encryption has emerged as a major issue in the debate over privacy rights.

That has put Silicon Valley at the center of a tug of war. Technology companies including Apple, Microsoft and Google have been moving to encrypt more of their corporate and customer data after learning that the National Security Agency and its counterparts were siphoning off digital communications and hacking into corporate data centers.

Yet law enforcement and intelligence agency leaders argue that such efforts thwart their ability to monitor kidnappers, terrorists and other adversaries. In Britain, Prime Minister David Cameron threatened to ban encrypted messages altogether. In the United States, Michael S. Rogers, the director of the N.S.A., proposed that technology companies be required to create a digital key to unlock encrypted data, but to divide the key into pieces and secure it so that no one person or government agency could use it alone.