A Washington-based privacy group held a meeting yesterday with Microsoft on the subject of the future of the software maker's authentication service, Passport.

Technical details of Passport, the single sign-on service that allows subscribers to log on to a collection of websites without re-entering personal information, was one of the topics discussed by the consumer advocacy group, the Center for Democracy and Technology (CDT).

Passport, a key component of Microsoft's upcoming .Net and HailStorm web services initiatives, is required for using some of Windows XP's newest features.

Ari Schwartz, a spokesman for the CDT, said the discussions took place on issues such as consumer privacy, government privacy, security and standards.

Schwartz said the CDT has set up these meetings with Microsoft to establish an open dialogue with the company as it moves forward with future product releases.

"We've been interested in authentication issues for some time," he said.

He also said the group meets regularly with major technology vendors about new technologies and their effect on consumer privacy.

Adam Sohn, Microsoft's manager for US .Net platform strategy, said the company was in Washington to directly inform the CDT of its plans.

"We want to provide the future of where we're going with Passport and with .Net and Hailstorm."

Sohn also pointed out that Microsoft is very concerned about privacy.

Last week, the Electronic Privacy Information Center (EPIC) and 12 other consumer and privacy groups, widened their complaint and once again asked the US Federal Trade Commission to investigate Microsoft's Passport.

The amended complaint included additional concerns over issues such as the tracking of internet users and children's privacy. It is also intended to clarify the original complaint by providing supplementary information.

Separately, Microsoft rival Sun Microsystems CEO Scott McNealy blasted Passport's centralised structure as a security, privacy and competitive nightmare.

McNealy said Sun's own technology would give internet users more options. "We're working on it. We know how to do it," he said.