This article was previously published under Q235284
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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) Remote Authentication Dial-In User Service (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.
Windows NT Server or Workstation 4.0
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:
152734how 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:
To resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
NOTE: Another solution is available by applying the RADIUS Roll-up hotfix described in the following article in Microsoft Knowledge Base:
239864 Availability of Internet Authentication Service SP6 Rollup Hotfix
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition.
This problem was first corrected in Windows NT Server 4.0 Service Pack 6 and Windows NT Server 4.0, Terminal Server Edition Service Pack 6.