Syskey Tool Reuses Keystream (248183)
The information in this article applies to:
- Microsoft Windows NT Server 4.0 Terminal Server Edition
- Microsoft Windows NT Server 4.0
- Microsoft Windows NT Workstation 4.0
- Microsoft Windows NT Server, Enterprise Edition 4.0
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.
RESOLUTIONWindows 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:
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
STATUSWindows NT Server or Workstation 4.0Microsoft 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 EditionMicrosoft has confirmed that this problem may cause a degree of security vulnerability in Windows NT Server 4.0, Terminal Server Edition.
| Modification Type: | Minor | Last Reviewed: | 9/26/2005 |
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| Keywords: | kbHotfixServer kbQFE kbbug kbfix kbgraphxlinkcritical kbQFE kbSecurity KB248183 |
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