Microsoft has joined the MIT Kerberos Consortium, an organization that develops the widely-used network authentication standard. It joins Apple, Google and Sun on the consortium's executive board.

Kerberos, which ships with most operating systems, is a suite of authentication protocols that can enable features such as single sign-on, where a single login and password can be used to access multiple Web sites or applications. It was developed as part of Massachusetts Institute of Technology's Project Athena in the 1980s.

While Microsoft has implemented Kerberos protocols in its Windows 2000, XP, Server 2003 and 2008 and Vista operating systems, the vendor was accused eight years ago of subverting the standard by adding proprietary extensions.

During Microsoft's U.S. antitrust trial, an MIT professor testified the vendor had extended the Kerberos specification used by its Windows 2000 OS such that a non-Microsoft server could not use the security features of the PC's OS.

That evidence contributed to the view that Microsoft gave lip service to the importance of interoperability, but implemented technical blocks that locked out competitors. Microsoft eventually released details on its modifications to Kerberos.

After both U.S. and European antitrust trials, Microsoft forcibly and voluntarily took steps to improve its documentation of protocols as well as open up more of its internal technical details.

Microsoft's participation in the Kerberos Consortium "shows Microsoft's continued and growing desire as of late to work with the open-source community and industry consortiums around interoperability," wrote Tom Kemp, CEO of Centrify, on his blog.

Centrify, a Microsoft partner, makes software called DirectControl that lets servers, workstations and devices from other vendors use Active Directory, which is Microsoft's authentication and provisioning technology. Authentication is accomplished using Kerberos, Kemp wrote.

Despite embroiling itself in controversy, Microsoft's involvement with Kerberos has also made use of the protocol more widespread, Kemp wrote.

"As we all know there are many out there that like to beat up Microsoft regarding security, but it is ironic that Microsoft by default delivers the added security of Kerberos as part and parcel of the Windows platform," Kemp wrote.