Microsoft has confirmed and elaborated on the role the National Security Agency played in helping secure the firm's Vista operating system, according to a report in Tuesday's Washington Post.

The eavesdropping and code-breaking agency has some of the best cryptographers in the world, and the NSA detailed a team to work with Microsoft on the new operating system, which is expected to be used eventually by hundreds of millions of computer users.

The relationship isn't exactly top secret: The newspaper noted that Microsoft's Web pages take note of the NSA's involvement in the "Windows Vista Security Guide."

The issue of possible NSA involvement with Microsoft operating systems has a long history. In 1999, Microsoft denied reports of NSA involvement in the code key used with the Microsoft Cryptographic API, although different sources claimed to have knowledge of NSA-Microsoft cooperation on the measure. This time, however, Microsoft and the NSA are acknowledging the agency's work on Vista. "Our intention is to help everyone with security," the NSA's Tony W. Sager told the Post. "It's partly a recognition that this is a commercial world. Our customers have spoken."

Sager, who is the NSA's chief of vulnerability analysis and operations group, said the agency established two units to examine Vista security issues. One group worked as the violator while the other sought to defend the operating system from incursions.

And, although Microsoft denied NSA assistance in 1999, the software company said it has used the NSA in the last four years to examine its operating systems including Windows XP consumer version and Windows Server 2003 for business customers, according to the newspaper report.