Event ID 28 — AD CS Registry Settings

Applies To: Windows Server 2008

Active Directory Certificate Services (AD CS) records critical configuration settings in the registry and may not start or function properly if this information becomes corrupted or is deleted.

Event Details

Product: Windows Operating System
ID: 28
Source: Microsoft-Windows-CertificationAuthority
Version: 6.0
Message: Active Directory Certificate Services did not start: The Certificate Revocation List Period string is invalid in the registry value HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CertSvc\Configuration\%1\CRLPeriod. Valid strings are "Seconds", "Minutes", "Hours", "Days", "Weeks", "Months" and "Years".


Fix the CRLPeriod registry key

By default, certification authority (CA) registry configuration information is located under **HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CertSvc\Configuration\**CA name.

If the event log message states that the CRLPeriod registry key is not valid, then you can update the registry entry with correct information.

The location of this registry key is HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CertSvc\Configuration\CA name\CRLPeriod.

Valid strings for this value are "Seconds," "Minutes," "Hours," "Days," "Weeks," "Months," and "Years."

To perform this procedure, you must have membership in local Administrators, or you must have been delegated the appropriate authority.

Caution: Incorrectly editing the registry might severely damage your system. Before making changes to the registry, you should back up any valued data.

To resolve registry-related problems:

  1. On the computer hosting the CA, click Start, type regedit, and press ENTER.
  2. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CertSvc\Configuration\CA name\CRLPeriod and correct the invalid registry configuration settings that you find. 
  3. Click Start, point to Administrative Tools, and click Certification Authority.
  4. Right-click the CA name, and click Restart.


To perform this procedure, you must have Manage CA permission, or you must have been delegated the appropriate authority.

To confirm the certification authority (CA) registry settings:

  1. After you have finished making any changes to registry settings for the CA, click Start, point to Administrative Tools, and click Certification Authority.
  2. Select the CA name, and click Restart
  3. Click Start, type cmd and press ENTER.
  4. Type certutil -getreg ca\security and press ENTER.
  5. If there are no more corrupt settings, the text -getreg command completed successfully will appear. 

AD CS Registry Settings

Active Directory Certificate Services