MPPE Keys Not Handled Correctly for a 128-Bit MS-CHAP Request

ID: Q235284

The information in this article applies to:

Microsoft Windows NT Server version 4.0
Microsoft Windows NT Server, Enterprise Edition version 4.0

SYMPTOMS

Microsoft Point-to-Point Encryption (MPPE) keys may not be encrypted correctly for a 128-bit Microsoft Challenge-Handshake Authentication Protocol (MS-CHAP) request. The Microsoft Internet Authentication service (IAS) Radius server and Routing and Remote Access Services (RRAS) correctly decrypt the MPPE keys, but do not correctly encrypt them.

This problem occurs if a user either dials into a third-party network access server (such as Cisco, Ascend, and so on) and uses 128-bit MS-CHAP on the Windows NT 4.0 Radius server, or dials into a Windows NT 4.0 RRAS server that is configured to be authenticated on a Microsoft Windows 2000 server.

RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:

http://www.microsoft.com/windows/servicepacks/

Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

STATUS

Microsoft has confirmed this to be a problem in Windows NT 4.0. This problem was first corrected in Windows NT 4.0 Service Pack 6.

Additional query words:

Keywords : kbbug4.00 kbfix4.00 NT4SP6Fix
Version : winnt:4.0
Platform : winnt
Issue type : kbbug