Saying electronic encryption increasingly threatens to blind law enforcement to criminal activity, the Justice Department insisted yesterday that its agents need the ability to secretly enter private property and disable security on personal computers despite concerns about privacy.

"We really are not crying wolf here," said Assistant Attorney General James Robinson, head of the department's criminal division, describing the proposal as merely an effort to update the laws governing search warrants to keep pace with technology. "No one, at the end of the day, will want a world in which, as a result of powerful encrypted communication and electronic data storage, there will be the inability to gather evidence of criminal activity."

After a story about the Justice Department's plans appeared in yesterday's Washington Post, civil liberties activists and some lawmakers attacked the idea as an unjustified expansion of police powers.

In a letter to Attorney General Janet Reno yesterday, Rep. Robert L. Barr Jr. (R-Ga.) described the Justice Department proposal as "patently absurd" and warned Reno that it "will seriously damage your credibility" in ongoing discussions about how to address the encryption issue.

"This proposal demonstrates how addicted federal law enforcement has become to electronic surveillance," Barr's letter said. "I urge you to retract this proposal and not send it to Congress."

The proposal would call on Congress to make it easier for federal agents to get sealed warrants signed by a judge permitting them to enter private property, search through computers for passwords and install devices that would override software programs that encrypt, or scramble, information. A document describing the proposal, a draft of legislation and an unsigned letter from the Justice Department to House Speaker J. Dennis Hastert (R-Ill.) have circulated to the Office of Management and Budget and other agencies in recent weeks.

Barr and Rep. Robert W. Goodlatte (R-Va.) said the draft legislation has little chance of gaining support in Congress. They noted that more than 250 lawmakers already have co-sponsored another measure that would encourage the use of encryption and prohibit a Clinton Administration proposal to mandate a "back door" in computer systems that would enable investigators to sidestep encryption.

Michael Froomkin, a law professor and encryption specialist at the University of Miami, said people should not be surprised by the proposal, given the inability of the Clinton administration to forge a consensus on encryption policy. But he said the proposed legislation would diminish privacy and greatly expand the ability of police to enter private property to search or modify computers.

"This is a logical outgrowth of the failure to control encryption," Froomkin said. "But it's very bad social policy."

Robinson and other law enforcement officials disagree. They say that few people understand the threat posed to law enforcement by the growth of encryption, which renders electronic files or communication unreadable for anyone who does not possess the proper code or "key."

But they added that the use of such secret warrants would be limited and closely controlled by the courts. "We realize that there needs to be a necessary balance," said Robinson, who declined to say how--or how often--such warrants would be used.

Two administration officials, who declined to be named, said the Justice Department likely will have to address at least some of the issues raised by critics before sending its draft legislation to Congress.