The plug-in will be written at Microsoft's Open Source Software Lab and released eventually to the open-source community, said Hank Janssen, the lab's program manager, at the TechEd IT Forum in Barcelona yesterday.
"We're actually writing the CardSpace extension, and they (The Mozilla Foundation) were very, very excited about it," according to Janssen.
CardSpace, which was formerly called InfoCard, aims to make it easier for users to manage and control the personal information they give to websites. Microsoft is promoting it as a way to replace usernames and passwords and provide a better defence against phishing and other types of online fraud.
The technology, which will be included in Windows Vista, stores the personal information on a user's computer. Microsoft's first attempt at identity management, called Passport, didn't catch on, partly because Microsoft planned to store users' information on its own servers, which raised privacy concerns.
The work with Firefox continues Microsoft's cooperative efforts with the Mozilla Foundation, the distributor of Firefox, that would have been unheard of until recently, Janssen said.
A group of Firefox developers came to Microsoft last month to ask questions about how to improve the browser's performance in Windows, Janssen said. Jokes circulated on discussion boards that black helicopters were flying overhead and that Microsoft might try to abduct the team, Janssen said.
Microsoft provided "unfettered" access to all the people they needed to talk to make Firefox work better with Vista, according to Janssen. "They even talked to the IE people."
The Mozilla team left intact after three days. As for as the black helicopters, "We're not that organised," Janssen said. "We would like to be, maybe."
No timetable has been set for when the plug-in will be completed or how it will be distributed, Microsoft said.