Mr. Barr also said companies that sell encryption with the goal of "ensuring that law enforcement will not be able to gain legal access" are "illegitimate."
Mr. Barr's attitude repeated the attitude of former officials of the Justice Department, including James B. Comey, F.B.I. Director, and Rod J. Rosenstein, the Attorney General, who took the lead on the law enforcement side of what has been a long-standing excitement with technology companies and advocate of privacy.
Privacy advocates have long argued that law enforcement can get most of the information it seeks by suing technology companies for user records and other data, and that these companies do not need to create ways to break into their own encryption away from the government.
But last year, F.B.I. acknowledged that it had improperly inflated the number of smartphones and other mobile devices it has not been able to open due to encryption, and the blame for a programming error.
Privacy defenders immediately attacked Mr. Barr's speech.
"Encryption protects consumers' reliably sensitive data," said Brett Max Kaufman, senior staff attorney at the Center for Democracy at the American Civil Liberties Union. "There is no way to give the FBI access to encrypted communications without giving the same access to any government. Technology Providers should continue to make their products as secure as possible and resist pressure from all governments to undermine the security of the tools they offer. "
Mr Barr assumes that the negative effects of encryption on law enforcement investigations" far outweigh the benefits of encryption to Protect Individuals, Business and the Nation, "said Riana Pfefferkorn, Assistant Director of Monitoring and Cyber Security at Stanford Center for the Internet and Society.