Microsoft KB Archive/254177

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Dial-Up or PPTP Client That Uses MSCHAPv1 Authentication Cannot Establish 40-Bit or 56-Bit Encryption Connection

Article ID: 254177

Article Last Modified on 2/28/2007


  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Professional Edition

This article was previously published under Q254177


On a dial-up or Point to Point Tunneling Protocol (PPTP) client that is specifically configured for MS-Challenge Handshake Authentication Protocol Version 1 (MSCHAPv1), you cannot establish a 40-bit or 56-bit encryption connection.


This behavior occurs when a password is longer than 14 characters. MSCHAPv1 does not support longer passwords. Note that this does not affect connections made using MSCHAPv2, which is the default in most cases. Also, this restriction does not affect 128-bit connections.


To resolve this issue, use a password no longer than 14 characters to allow dial-up or PPTP clients that are specifically configured to use MSCHAPv1 authentication to establish a 40-bit or 56-bit encryption connection.

Additional query words: win2krelnotes

Keywords: kbprb KB254177