Clear method of the Win32_Tpm class
The Clear method of the Win32_Tpm class resets the TPM to its factory-default state. A TPM owner can use this method to cancel TPM ownership and invalidate cryptographic materials created by the previous owner. This method suspends BitLocker if calling could cause BitLocker recovery to be required. BitLocker would automatically resume once TPM has been provisioned.
Caution
By clearing the TPM, you will lose all TPM keys created and used by applications. If these keys were used to encrypt data, ensure that you have another way to access the data before clearing the TPM.
Syntax
uint32 Clear(
[in, optional] string OwnerAuth
);
Parameters
-
OwnerAuth [in, optional]
-
Type: string
A string that identifies the TPM owner. This string must be a base64-encoded string that contains exactly 20 bytes of binary data. Use the ConvertToOwnerAuth method to translate a passphrase to this expected format. The OwnerAuth parameter is read from the registry if none is provided.
Return value
Type: uint32
All TPM errors as well as errors specific to TPM Base Services can be returned.
The following table lists some of the common return codes.
| Return code/value | Description |
|---|---|
|
The method was successful. |
|
The provided owner authorization value cannot perform the request. |
|
The TPM is defending against dictionary attacks and is in a time-out period. For more information, see the ResetAuthLockOut method. |
Remarks
Running this method can help prepare a TPM-equipped computer for recycling.
To clear the TPM but no longer have the TPM owner authorization, you need physical access to the computer. The SetPhysicalPresenceRequest method includes functionality to help clear the TPM without TPM owner authorization.
Managed Object Format (MOF) files contain the definitions for Windows Management Instrumentation (WMI) classes. MOF files are not installed as part of the Windows SDK. They are installed on the server when you add the associated role by using the Server Manager. For more information about MOF files, see Managed Object Format (MOF).
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows Vista [desktop apps only] |
| Minimum supported server |
Windows Server 2008 [desktop apps only] |
| Namespace |
Root\CIMV2\Security\MicrosoftTpm |
| MOF |
|
| DLL |
|
See also