Microsoft KB Archive/248183

= Syskey Tool Reuses Keystream =

Article ID: 248183

Article Last Modified on 3/22/2007

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition

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This article was previously published under Q248183



SYMPTOMS
A cryptographic error in the Syskey tool makes offline password attacks easier than previously believed. Syskey reuses keystream when encrypting certain elements in the Security Accounts Manager (SAM) database, making the tool vulnerable to an attack using a known cryptanalytic method. This vulnerability could allow offline password attacks to be mounted against a Syskey-protected SAM database.



CAUSE
Passwords in the SAM database are stored in hashed form to prevent a user who gains access to the database from reading the passwords. However, offline password attacks are still possible if an attacker obtains a copy of the database and is willing to devote the time needed to perform an exhaustive search of all possible passwords. The Syskey tool is designed to prevent such attacks by strongly encrypting the SAM database using 128-bit cryptography. However, a flaw in the implementation results in multiple database entries being encrypted with the same keystream. This renders the encryption susceptible to a known attack.



Windows NT Server or Workstation 4.0
To resolve this problem, obtain the individual package referenced below or obtain the Windows NT 4.0 Security Rollup Package. For additional information on the SRP, click the article number below to view the article in the Microsoft Knowledge Base:

299444 Post-Windows NT 4.0 Service Pack 6a Security Rollup Package (SRP)

The following files are available for download from the Microsoft Download Center:

Download Q248183.Exe for x86-based computers now

Download Q248183.Exe for Alpha-based computers now

The English version of this fix should have the following file attributes or later:

  Date      Time        Size      File name    Platform -  12/06/1999   06:52p   155,408   Lsasrv.dll   x86 12/06/1999  06:53p   174,352   Samsrv.dll   x86

12/06/1999  06:51p   253,712   Lsasrv.dll   Alpha 12/06/1999  06:51p   290,064   Samsrv.dll   Alpha

Windows NT Server 4.0, Terminal Server Edition
To resolve this problem, obtain the Windows NT Server 4.0, Terminal Server Edition, Security Rollup Package (SRP). For additional information about the SRP, click the article number below to view the article in the Microsoft Knowledge Base:

317636 Windows NT Server 4.0, TerminalServer Edition, Security Rollup Package



Windows NT Server or Workstation 4.0
Microsoft has confirmed that this problem may cause a degree of security vulnerability in Windows NT 4.0 Server and Workstation.

Windows NT Server 4.0, Terminal Server Edition
Microsoft has confirmed that this problem may cause a degree of security vulnerability in Windows NT Server 4.0, Terminal Server Edition.



MORE INFORMATION
For additional information about the Syskey tool, click the article number below to view the article in the Microsoft Knowledge Base:

143475 Windows NT System Key Permits Strong Encryption of the SAM

Additional query words: security_patch cracking kbtsesrp

Keywords: kbhotfixserver kbqfe kbbug kbfix kbgraphxlinkcritical kbqfe kbsecurity KB248183

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