Clearing a TPM is not an ordinary “restart”; it returns the Trusted Platform Module to its default state. Microsoft’s Clear-Tpm documentation is explicit: the operation removes the owner authorization value and keys stored in the TPM. Features that depend on those keys may need recovery or reenrollment, or may lose access permanently.
Irreversible boundary: A clear can invalidate TPM key protectors for BitLocker/device encryption, Windows Hello/Hello for Business credentials, virtual smart cards, and other TPM-bound private keys created by applications or certificate providers. A non-exportable private key inside the TPM cannot be “rolled back” after clearing. Continue only after owner authorization, a complete inventory, off-device recovery information, and verified backups are all in place.
Table of Contents
Confirm the Device, Documentation, and Management Boundary
There is no single TPM menu shared by every ThinkPad generation and model. A machine may use a discrete TPM, Intel PTT, AMD fTPM, or Microsoft Pluton; menu names, physical-confirmation keys, chip-switch behavior, and UEFI versions differ. On some Lenovo models, merely switching the security-chip type clears its contents.
On Lenovo Support, select the product by its exact machine type/model (MTM) and find the User Guide, BIOS Simulator, or Lenovo notice that matches that model, current UEFI release, and operating system. Never treat another ThinkPad’s keys or Security Chip path as instructions for yours.
Stop and hand the device to IT/its administrator in any of these cases:
- company, school, leased, managed, or Autopilot/Intune/domain-managed device;
- unknown owner of the data, recovery keys, certificates, or TPM-clear authority;
- UEFI supervisor password, organizational policy, or remote-attestation requirement;
- the clear is part of repair, mainboard replacement, redeployment, or compliance work without an approved change record and recovery plan.
What a Clear Can Affect
| TPM consumer | Possible consequence | Recovery evidence required before clearing |
|---|---|---|
| BitLocker/device encryption | TPM protector no longer unseals; startup enters BitLocker recovery | Every encrypted volume has a non-TPM recovery route; retrieve it from another device and match the recovery-key ID |
| Windows Hello/Hello for Business | PIN, biometrics, or device key no longer works | Tested password, security key, Temporary Access Pass, or organization-approved alternative sign-in; explicit reenrollment plan |
| TPM virtual smart card | Virtual-card private key in the TPM is lost; certificate can no longer authenticate | PKI administrator confirms revocation, reissue, and alternative authentication; never assume the private key is exportable |
| TPM certificate/application private key | VPN, Wi-Fi, code signing, device authentication, or application decryption can fail | Identify each TPM-bound key and its backup, reissue, or recovery owner |
| Device attestation and deployment | Health attestation, Autopilot, or MDM identity can require rebuilding | IT-approved reenrollment/reimage procedure and network-access route |
| Legacy Lenovo Client Security Solution | Key, ownership, and sign-in integration can fail | Migration to a supported platform; legacy recovery material verified offline |
This table is not a complete asset inventory. If you do not know whether something uses the TPM, treat it as TPM-dependent until the application owner or organizational PKI/identity team confirms otherwise.
Read-Only Evidence Before Clearing
Use an elevated PowerShell session to read status. These commands do not clear the TPM or display a 48-digit BitLocker recovery password:
Get-CimInstance Win32_ComputerSystemProduct | Select-Object Vendor,Name,Version,IdentifyingNumber
Get-CimInstance Win32_BIOS | Select-Object SMBIOSBIOSVersion,ReleaseDate
Get-Tpm
Get-TpmEndorsementKeyInfo
Get-BitLockerVolume | Select-Object MountPoint,VolumeStatus,ProtectionStatus,EncryptionMethod,KeyProtectorRecord the exact model/MTM, UEFI release, TPM manufacturer/version, TpmPresent/TpmReady, every encrypted volume and protector type, fault text, time, and approval reference. IdentifyingNumber, endorsement-key information, recovery-key IDs, and device identifiers should not be public; redact them before sharing.
Do not retain the old article’s assumption that obtaining the EK public key requires a clear. Current Windows offers the read-only Get-TpmEndorsementKeyInfo. If only public endorsement information is needed for authorized research, use read-only access first and do not publish output that can identify the device.
Go/No-Go Gate Before Clearing
Every item must be answered “yes”:
- Specific reason: Windows Security reports a concrete TPM error that calls for clearing, an exact-model Lenovo/Microsoft notice requires it, or an approved repair/redeployment workflow explicitly requires it.
- Owner authorization: The data owner and device administrator approve; the maintenance window and accountable operator are recorded.
- Recoverable backup: User data and critical application configuration are backed up and readable from another device.
- BitLocker is recoverable: For every encrypted volume, retrieve matching recovery information from a Microsoft account, Microsoft Entra ID, AD DS, or the approved secure store. “It should be backed up” is not evidence.
- Alternative sign-in works: A Windows password, security key, or organization-approved alternative is tested and does not depend on the TPM being cleared.
- Other keys are handled: Hello, virtual smart cards, certificates, VPN, Wi-Fi, application keys, device attestation, and deployment identity each have a reissue/reenrollment plan.
- Model documentation matches: The Lenovo document’s model, MTM, UEFI version, and screen wording match the physical machine.
- Rollback boundary is understood: Firmware configuration, accounts, and external backups can be restored; keys already cleared from the TPM cannot.
Stop if any answer is “no” or “unknown.” Clearing the TPM is not a way to recover a Windows password, bypass organizational management, fix general performance, or erase storage-drive data.
Choose One Supported Clear Entry Point
Different entry points can ultimately issue the same destructive TPM Clear request. Use only the one named by the approved workflow; do not try several in succession.
| Entry point | When it applies | Boundary |
|---|---|---|
| Windows Security | Current Windows reports a security-processor fault and offers Clear TPM | Follow the displayed normal restart and physical confirmation; prompts vary by model |
tpm.msc | A Microsoft/Lenovo support workflow explicitly names TPM Management | All go/no-go gates still apply; it is not a universal substitute for a legacy owner password |
| PowerShell | An administrator’s written change procedure specifies Clear-Tpm | The command immediately schedules a destructive operation; restart may require physical confirmation |
| Lenovo UEFI | The exact model’s User Guide or notice specifies its menu and confirmation | Do not guess menus, switch chip type to reveal an option, or copy the X200 hidden-state sequence |
Windows Security or tpm.msc
The current Windows Security path is Device security → Security processor details → Security processor troubleshooting → Clear TPM. If the approved procedure specifies tpm.msc, open TPM Management and select Clear TPM. For either route:
- Recheck recovery information and device identity.
- Connect reliable power, save work, and close applications.
- Read the entire warning and confirm only when it clearly describes clearing the current TPM.
- Use the normal restart provided by Windows; never force power off.
- Complete physical-presence confirmation only when the actual screen matches the exact-model documentation. If the key, chip name, or operation differs, cancel and stop.
Windows may automatically handle some BitLocker suspension steps, but that does not replace a verified recovery key. If the exact Microsoft/Lenovo/organizational procedure requires BitLocker suspension, limit it to the documented reboot window and record the checkpoint for resuming protection. Do not make permanent decryption or disabling security a default prerequisite.
Controlled PowerShell Route
The following is a destructive operation, not a diagnostic command. Run it in elevated PowerShell only after every gate passes and the written procedure explicitly selects the PPI route:
Clear-Tpm -UsePPIMicrosoft documents that the clear takes effect after restart and can require user confirmation. If the platform does not support this route, returns a policy/permission error, or shows a prompt that differs from the documentation, do not switch to an owner-authorization file, remote execution, or repeated clears. Preserve the error and escalate to IT, Lenovo, or Microsoft Support.
Lenovo UEFI Route
Use UEFI only when the exact-model documentation explicitly describes Clear Security Chip, Clear TPM, or an equivalent operation. Record all relevant UEFI values before entry, and follow that document’s normal save, exit, and restart sequence.
Do not use these legacy tricks to reveal a clear option: cycling Active/Inactive/Disable, changing PTT/fTPM/Pluton/Discrete TPM type, disabling Secure Boot, restoring all BIOS defaults, forcing power off, or looking for hidden menus. On some modern Lenovo models, switching the security chip itself clears BitLocker keys, so “trying another option” can already cross the irreversible boundary.
Recovery and Verification After the Clear
Windows normally reprovisions the TPM after a successful clear, but business recovery is not automatic. Verify in this order:
- Boot normally. If BitLocker recovery appears, enter only an escrowed key whose ID matches the screen; do not clear the TPM again.
- Rerun the read-only inventory and confirm
TpmPresentandTpmReadyare expected and that manufacturer/version still match the exact model. - Confirm every BitLocker/device-encryption volume is unlocked and its protection status and non-TPM recovery protector meet organizational policy. If the procedure suspended protection, resume it through the approved step and verify one normal restart.
- Sign in with the tested alternative credential, then reset Windows Hello PIN/biometrics or have the organization reprovision Hello for Business.
- Have PKI/application owners revoke and reissue virtual smart cards, TPM certificates, and other lost TPM-bound credentials; test VPN, Wi-Fi, signing, and business applications.
- On managed devices, IT verifies Entra/AD, MDM, Autopilot, and device health attestation.
- Record results, time, approval, model, and the location of recovery information; never place actual recovery keys or private keys in tickets, blogs, or public logs.
Perform at least two controlled boot tests, including one cold boot after shutdown. Close the maintenance window only after there is no repeated BitLocker recovery, Hello fallback, TPM error, or management-compliance failure.
Stop Conditions and Recovery Boundary
| State | Immediate action | Can it be “rolled back”? |
|---|---|---|
| Clear is not yet confirmed and recovery key is missing | Cancel and exit | Yes; no clear occurred |
| Firmware screen differs from model documentation | Do not save or guess keys; photograph only nonsensitive evidence | Unsaved configuration can be abandoned |
| Clear was confirmed or TPM is at default state | Do not repeat; enter recovery/reenrollment workflow | Old TPM keys cannot be restored; only off-device recovery material can help |
| Startup requests BitLocker recovery | Locate the correct escrowed key by recovery-key ID; contact IT | Data access can recover; cleared TPM keys cannot be recreated |
| Windows Hello fails | Use password/security key/approved alternative and reenroll | Reenrollment is possible; old TPM credential is not recoverable |
| TPM is absent, unready, or manufacturer/version is unexpected | If UEFI was changed, restore only the recorded original setting; stop and contact Lenovo/Microsoft | Configuration may recover; hardware/key issues need support |
| Management, attestation, or Autopilot fails | Stop user action; IT follows the tenant recovery process | Depends on organizational identity/deployment records |
If no recovery key exists, there is no safe bypass. Do not try another clear, disable TPM/Secure Boot, reset the whole computer, or alter the boot chain; these can expand data loss.
Explicit Boundary for the Historical X200 Observation
The source recorded a ThinkPad X200 with the old Client Security Solution: change Security Chip state, restart, then force power off to reveal a hidden Clear Security Chip. That is a historical observation, not a current universal Lenovo procedure, and it must not be reproduced on modern ThinkPads.
Even if the physical machine is an X200, it is a legacy platform. Start from the archived Lenovo manual for its exact version, an isolated environment, a full-disk image, and verified recovery material. Do not assume that the same BIOS, TPM firmware, or data state exists because the old procedure once worked. For EK or other public information, prefer read-only interfaces and never clear a real user device merely for observation.
Current Official References
- Microsoft: Device security and Clear TPM in Windows Security
- Microsoft: TPM firmware updates and pre-clear warnings
- Microsoft: How Windows uses the TPM
- Microsoft PowerShell: Clear-Tpm
- Microsoft PowerShell: TrustedPlatformModule cmdlets
- Microsoft PowerShell: Get-BitLockerVolume
- Microsoft: BitLocker recovery and key escrow overview
- Microsoft: TPM virtual smart cards
- Lenovo: Find the BIOS Simulator by product name
- Current Lenovo User Guide: Find Guides & Manuals by exact product
- Lenovo model-limited example: Switching the security chip clears keys on selected AMD ThinkPads
Historical Source Archive (2011, for Provenance Only)
Warning and archive note: The following is the complete visible
source_exportbody with trailing whitespace normalized and eleven unique dead HTTP image targets replaced by labeled placeholders. It contains high-risk steps to force power off, cycle hidden legacy BIOS states, and clear all TPM keys. The four-backtick plain-text fence prevents it from becoming the current operational guide. The historical attribution URL remains inside the fence; nothing else was omitted or rewritten, and the original image URLs remain insource_export/Git provenance.
Thinkpad笔记本清除TPM信息的方法
我用的是Thinkpad X200笔记本，最近在Windows平台下对TPM做研究时发现要得到EK的公钥部分，必须ClearTPM，同学的Infineon TPM机子上可以通过BIOS清除掉TPM的一些信息，但X200的BIOS中没有提供这一项，其实是有的，只是被隐藏了起来，以下是清除方法：
开机时按F1进入BIOS：
图1
依次进入TPM的设置页面：
图2
图3
这就是TPM的设置页面，目前是Active状态：
图4
首先改为Active以外的状态（共包括Active、Inactive、Disable），如Disable
图5
然后按F10保存信息，确认后将自动重启：
图6
重启后以同样方法进入到BIOS的TPM设置页面，这时改回Active状态：
图7
确认后，这时，不要按F10，而是按电源键强制关机：
图8
关机后开机，再次以同样的方法进入TPM设置界面，这时隐藏的“Clear Security Chip”选项就出来了：
图9
确认后将清除掉TPM的所有密钥信息（除EK以外），当然，Ownership也将不存在。注意旁边的说明，如果有重要数据一定要注意了，备份工作要做好，否则密钥没有了，数据也解不开了。
图10
按F10保存并重启：
图11
Clear掉之后，就可以以初始的状态研究TPM了，不过每次开机Client Security Solution都会提试输入密码来恢复密钥并Take Ownership，此时可以取消跳过。
原文地址：
http://www.cnblogs.com/cxun/archive/2009/10/19/1586209.html