DOCUMENT:Q248183 08-MAY-2002 [winnt] TITLE :Syskey Tool Reuses Keystream PRODUCT :Microsoft Windows NT PROD/VER::4.0 OPER/SYS: KEYWORDS:kbtool kbSecurity kbWinNT400PreSP7Fix kbgraphxlinkcritical ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server version 4.0, Terminal Server Edition - Microsoft Windows NT Server version 4.0 - Microsoft Windows NT Workstation version 4.0 - Microsoft Windows NT Server, Enterprise Edition version 4.0 ------------------------------------------------------------------------------- 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. RESOLUTION ========== 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: Q299444 Post-Windows NT 4.0 Service Pack 6a Security Rollup Package (SRP) The following files are available for download from the Microsoft Download Center: DownloadDownload Q248183.Exe for x86-based computers now (http://www.microsoft.com/downloads/release.asp?ReleaseID=16798) DownloadDownload Q248183.Exe for Alpha-based computers now (http://www.microsoft.com/downloads/release.asp?ReleaseID=16799) 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: Q317636 Windows NT Server 4.0, Terminal Server Edition, Security Rollup Package STATUS ====== Windows NT Server or Workstation 4.0 ------------------------------------ Microsoft has confirmed that this problem could result in some 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 could result in some 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: Q143475 Windows NT System Key Permits Strong Encryption of the SAM Additional query words: security_patch cracking kbtsesrp ====================================================================== Keywords : kbtool kbSecurity kbWinNT400PreSP7Fix kbgraphxlinkcritical Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch Version : :4.0 Hardware : ALPHA x86 Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.