diff --git a/windows/security/information-protection/tpm/backup-tpm-recovery-information-to-ad-ds.md b/windows/security/information-protection/tpm/backup-tpm-recovery-information-to-ad-ds.md index 1f2a9067e6..8f9951dfee 100644 --- a/windows/security/information-protection/tpm/backup-tpm-recovery-information-to-ad-ds.md +++ b/windows/security/information-protection/tpm/backup-tpm-recovery-information-to-ad-ds.md @@ -15,4 +15,6 @@ appliesto: # Backup the TPM recovery information to AD DS -With Windows 11, you can back up a computer's Trusted Platform Module (TPM) information to Active Directory Domain Services (AD DS). By doing this, you can use AD DS to administer the TPM from a remote computer. The procedure is the same as it was for Windows 8.1. For more information, see [Backup the TPM Recovery Information to AD DS](/previous-versions/windows/it-pro/windows-8.1-and-8/dn466534(v=ws.11)). +In Windows 11, you can backup a device's Trusted Platform Module (TPM) information to Active Directory Domain Services (AD DS), enabling remote management of the TPM. + +For more information, see [Backup the TPM Recovery Information to AD DS](/previous-versions/windows/it-pro/windows-8.1-and-8/dn466534(v=ws.11)). diff --git a/windows/security/information-protection/tpm/how-windows-uses-the-tpm.md b/windows/security/information-protection/tpm/how-windows-uses-the-tpm.md index f886cc3480..be0cadec4a 100644 --- a/windows/security/information-protection/tpm/how-windows-uses-the-tpm.md +++ b/windows/security/information-protection/tpm/how-windows-uses-the-tpm.md @@ -23,7 +23,7 @@ The TPM is a cryptographic module that enhances computer security and privacy. P Historically, TPMs have been discrete chips soldered to a computer's motherboard. Such implementations allow the computer's original equipment manufacturer (OEM) to evaluate and certify the TPM separate from the rest of the system. Although discrete TPM implementations are still common, they can be problematic for integrated devices that are small or have low power consumption. Some newer TPM implementations integrate TPM functionality into the same chipset as other platform components while still providing logical separation similar to discrete TPM chips. -TPMs are passive: they receive commands and return responses. To realize the full benefit of a TPM, the OEM must carefully integrate system hardware and firmware with the TPM to send it commands and react to its responses. TPMs were originally designed to provide security and privacy benefits to a platform's owner and users, but newer versions can provide security and privacy benefits to the system hardware itself. Before it can be used for advanced scenarios, a TPM must be provisioned. Windows automatically provisions a TPM, but if the operating system is reinstalled, the TPM may be required to be explicitly re-provisioned before it can use all the TPM's features. +TPMs are passive: they receive commands and return responses. To realize the full benefit of a TPM, the OEM must carefully integrate system hardware and firmware with the TPM to send it commands and react to its responses. TPMs were originally designed to provide security and privacy benefits to a platform's owner and users, but newer versions can provide security and privacy benefits to the system hardware itself. Before it can be used for advanced scenarios, a TPM must be provisioned. Windows automatically provisions a TPM, but if the operating system is reinstalled, the TPM may be required to be explicitly reprovisioned before it can use all the TPM's features. The Trusted Computing Group (TCG) is the nonprofit organization that publishes and maintains the TPM specification. The TCG exists to develop, define, and promote vendor-neutral, global industry standards that support a hardware-based root of trust for interoperable trusted computing platforms. The TCG also publishes the TPM specification as the international standard ISO/IEC 11889, using the Publicly Available Specification Submission Process that the Joint Technical Committee 1 defines between the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). @@ -47,9 +47,9 @@ The Platform Crypto Provider, introduced in the Windows 8 operating system, expo - **Key protection**. The Platform Crypto Provider can create keys in the TPM with restrictions on their use. The operating system can load and use the keys in the TPM without copying the keys to system memory, where they're vulnerable to malware. The Platform Crypto Provider can also configure keys that a TPM protects so that they aren't removable. If a TPM creates a key, the key is unique and resides only in that TPM. If the TPM imports a key, the Platform Crypto Provider can use the key in that TPM, but that TPM isn't a source for making more copies of the key or enabling the use of copies elsewhere. In sharp contrast, software solutions that protect keys from copying are subject to reverse-engineering attacks, in which someone figures out how the solution stores keys or makes copies of keys while they are in memory during use. -- **Dictionary attack protection**. Keys that a TPM protects can require an authorization value such as a PIN. With dictionary attack protection, the TPM can prevent attacks that attempt a large number of guesses to determine the PIN. After too many guesses, the TPM simply returns an error saying no more guesses are allowed for a period of time. Software solutions might provide similar features, but they cannot provide the same level of protection, especially if the system restarts, the system clock changes, or files on the hard disk that count failed guesses are rolled back. In addition, with dictionary attack protection, authorization values such as PINs can be shorter and easier to remember while still providing the same level of protection as more complex values when using software solutions. +- **Dictionary attack protection**. Keys that a TPM protects can require an authorization value such as a PIN. With dictionary attack protection, the TPM can prevent attacks that attempt a large number of guesses to determine the PIN. After too many guesses, the TPM simply returns an error saying no more guesses are allowed for a period of time. Software solutions might provide similar features, but they can't provide the same level of protection, especially if the system restarts, the system clock changes, or files on the hard disk that count failed guesses are rolled back. In addition, with dictionary attack protection, authorization values such as PINs can be shorter and easier to remember while still providing the same level of protection as more complex values when using software solutions. -These TPM features give Platform Crypto Provider distinct advantages over software-based solutions. A practical way to see these benefits in action is when using certificates on a Windows device. On platforms that include a TPM, Windows can use the Platform Crypto Provider to provide certificate storage. Certificate templates can specify that a TPM use the Platform Crypto Provider to protect the key associated with a certificate. In mixed environments, where some computers might not have a TPM, the certificate template could prefer the Platform Crypto Provider over the standard Windows software provider. If a certificate is configured as not able to be exported, the private key for the certificate is restricted and cannot be exported from the TPM. If the certificate requires a PIN, the PIN gains the TPM's dictionary attack protection automatically. +These TPM features give Platform Crypto Provider distinct advantages over software-based solutions. A practical way to see these benefits in action is when using certificates on a Windows device. On platforms that include a TPM, Windows can use the Platform Crypto Provider to provide certificate storage. Certificate templates can specify that a TPM use the Platform Crypto Provider to protect the key associated with a certificate. In mixed environments, where some computers might not have a TPM, the certificate template could prefer the Platform Crypto Provider over the standard Windows software provider. If a certificate is configured as not able to be exported, the private key for the certificate is restricted and can't be exported from the TPM. If the certificate requires a PIN, the PIN gains the TPM's dictionary attack protection automatically. ## Virtual Smart Card @@ -59,7 +59,7 @@ Smart cards are physical devices that typically store a single certificate and t In Windows, the *Virtual Smart Card* feature allows the TPM to mimic a permanently inserted smart card. The TPM becomes *something the user has* but still requires a PIN. While physical smart cards limit the number of PIN attempts before locking the card and requiring a reset, a virtual smart card relies on the TPM's dictionary attack protection to prevent too many PIN guesses. -For TPM-based virtual smart cards, the TPM protects the use and storage of the certificate private key, so that it cannot be copied when it is in use or stored and used elsewhere. Using a component that is part of the system rather than a separate physical smart card, can reduce total cost of ownership. The *lost card* or *card left at home* scenarios are not applicable, and the benefits of smart card-based multifactor authentication is preserved. For users, virtual smart cards are simple to use, requiring only a PIN to unlock. Virtual smart cards support the same scenarios that physical smart cards support, including signing in to Windows or authenticating for resource access. +For TPM-based virtual smart cards, the TPM protects the use and storage of the certificate private key, so that it can't be copied when it is in use or stored and used elsewhere. Using a component that is part of the system rather than a separate physical smart card, can reduce total cost of ownership. The *lost card* or *card left at home* scenarios are not applicable, and the benefits of smart card-based multifactor authentication is preserved. For users, virtual smart cards are simple to use, requiring only a PIN to unlock. Virtual smart cards support the same scenarios that physical smart cards support, including signing in to Windows or authenticating for resource access. ## Windows Hello for Business @@ -82,11 +82,11 @@ For Windows Hello for Business, Microsoft can fill the role of the identity CA. BitLocker provides full-volume encryption to protect data at rest. The most common device configuration splits the hard drive into several volumes. The operating system and user data reside on one volume that holds confidential information, and other volumes hold public information such as boot components, system information and recovery tools. (These other volumes are used infrequently enough that they do not need to be visible to users.) Without more protections in place, if the volume containing the operating system and user data is not encrypted, someone can boot another operating system and easily bypass the intended operating system's enforcement of file permissions to read any user data. -In the most common configuration, BitLocker encrypts the operating system volume so that if the computer or hard disk is lost or stolen when powered off, the data on the volume remains confidential. When the computer is turned on, starts normally, and proceeds to the Windows logon prompt, the only path forward is for the user to log on with his or her credentials, allowing the operating system to enforce its normal file permissions. If something about the boot process changes, however—for example, a different operating system is booted from a USB device—the operating system volume and user data cannot be read and are not accessible. The TPM and system firmware collaborate to record measurements of how the system started, including loaded software and configuration details such as whether boot occurred from the hard drive or a USB device. BitLocker relies on the TPM to allow the use of a key only when startup occurs in an expected way. The system firmware and TPM are carefully designed to work together to provide the following capabilities: +In the most common configuration, BitLocker encrypts the operating system volume so that if the computer or hard disk is lost or stolen when powered off, the data on the volume remains confidential. When the computer is turned on, starts normally, and proceeds to the Windows logon prompt, the only path forward is for the user to log on with his or her credentials, allowing the operating system to enforce its normal file permissions. If something about the boot process changes, however—for example, a different operating system is booted from a USB device—the operating system volume and user data can't be read and are not accessible. The TPM and system firmware collaborate to record measurements of how the system started, including loaded software and configuration details such as whether boot occurred from the hard drive or a USB device. BitLocker relies on the TPM to allow the use of a key only when startup occurs in an expected way. The system firmware and TPM are carefully designed to work together to provide the following capabilities: -- **Hardware root of trust for measurement**. A TPM allows software to send it commands that record measurements of software or configuration information. This information can be calculated using a hash algorithm that essentially transforms a lot of data into a small, statistically unique hash value. The system firmware has a component called the Core Root of Trust for Measurement (CRTM) that is implicitly trusted. The CRTM unconditionally hashes the next software component and records the measurement value by sending a command to the TPM. Successive components, whether system firmware or operating system loaders, continue the process by measuring any software components they load before running them. Because each component's measurement is sent to the TPM before it runs, a component cannot erase its measurement from the TPM. (However, measurements are erased when the system is restarted.) The result is that at each step of the system startup process, the TPM holds measurements of boot software and configuration information. Any changes in boot software or configuration yield different TPM measurements at that step and later steps. Because the system firmware unconditionally starts the measurement chain, it provides a hardware-based root of trust for the TPM measurements. At some point in the startup process, the value of recording all loaded software and configuration information diminishes and the chain of measurements stops. The TPM allows for the creation of keys that can be used only when the platform configuration registers that hold the measurements have specific values. +- **Hardware root of trust for measurement**. A TPM allows software to send it commands that record measurements of software or configuration information. This information can be calculated using a hash algorithm that essentially transforms a lot of data into a small, statistically unique hash value. The system firmware has a component called the Core Root of Trust for Measurement (CRTM) that is implicitly trusted. The CRTM unconditionally hashes the next software component and records the measurement value by sending a command to the TPM. Successive components, whether system firmware or operating system loaders, continue the process by measuring any software components they load before running them. Because each component's measurement is sent to the TPM before it runs, a component can't erase its measurement from the TPM. (However, measurements are erased when the system is restarted.) The result is that at each step of the system startup process, the TPM holds measurements of boot software and configuration information. Any changes in boot software or configuration yield different TPM measurements at that step and later steps. Because the system firmware unconditionally starts the measurement chain, it provides a hardware-based root of trust for the TPM measurements. At some point in the startup process, the value of recording all loaded software and configuration information diminishes and the chain of measurements stops. The TPM allows for the creation of keys that can be used only when the platform configuration registers that hold the measurements have specific values. -- **Key used only when boot measurements are accurate**. BitLocker creates a key in the TPM that can be used only when the boot measurements match an expected value. The expected value is calculated for the step in the startup process when Windows Boot Manager runs from the operating system volume on the system hard drive. Windows Boot Manager, which is stored unencrypted on the boot volume, needs to use the TPM key so that it can decrypt data read into memory from the operating system volume and startup can proceed using the encrypted operating system volume. If a different operating system is booted or the configuration is changed, the measurement values in the TPM will be different, the TPM will not let Windows Boot Manager use the key, and the startup process cannot proceed normally because the data on the operating system cannot be decrypted. If someone tries to boot the system with a different operating system or a different device, the software or configuration measurements in the TPM will be wrong and the TPM will not allow use of the key needed to decrypt the operating system volume. As a failsafe, if measurement values change unexpectedly, the user can always use the BitLocker recovery key to access volume data. Organizations can configure BitLocker to store the recovery key-in Active Directory Domain Services (AD DS). +- **Key used only when boot measurements are accurate**. BitLocker creates a key in the TPM that can be used only when the boot measurements match an expected value. The expected value is calculated for the step in the startup process when Windows Boot Manager runs from the operating system volume on the system hard drive. Windows Boot Manager, which is stored unencrypted on the boot volume, needs to use the TPM key so that it can decrypt data read into memory from the operating system volume and startup can proceed using the encrypted operating system volume. If a different operating system is booted or the configuration is changed, the measurement values in the TPM will be different, the TPM will not let Windows Boot Manager use the key, and the startup process can't proceed normally because the data on the operating system can't be decrypted. If someone tries to boot the system with a different operating system or a different device, the software or configuration measurements in the TPM will be wrong and the TPM will not allow use of the key needed to decrypt the operating system volume. As a failsafe, if measurement values change unexpectedly, the user can always use the BitLocker recovery key to access volume data. Organizations can configure BitLocker to store the recovery key-in Active Directory Domain Services (AD DS). Device hardware characteristics are important to BitLocker and its ability to protect data. One consideration is whether the device provides attack vectors when the system is at the logon screen. For example, if the Windows device has a port that allows direct memory access so that someone can plug in hardware and read memory, an attacker can read the operating system volume's decryption key from memory while at the Windows logon screen. To mitigate this risk, organizations can configure BitLocker so that the TPM key requires both the correct software measurements and an authorization value. The system startup process stops at Windows Boot Manager, and the user is prompted to enter the authorization value for the TPM key or insert a USB device with the value. This process stops BitLocker from automatically loading the key into memory where it might be vulnerable, but has a less desirable user experience. @@ -127,9 +127,9 @@ Mobile device management (MDM) solutions can receive simple security assertions Credential Guard is a new feature in Windows that helps protect Windows credentials in organizations that have deployed AD DS. Historically, a user's credentials (such as a logon password) were hashed to generate an authorization token. The user employed the token to access resources that he or she was permitted to use. One weakness of the token model is that malware that had access to the operating system kernel could look through the computer's memory and harvest all the access tokens currently in use. The attacker could then use harvested tokens to log on to other machines and collect more credentials. This kind of attack is called a "pass the hash" attack, a malware technique that infects one machine to infect many machines across an organization. -Similar to the way Microsoft Hyper-V keeps virtual machines (VMs) separate from one another, Credential Guard uses virtualization to isolate the process that hashes credentials in a memory area that the operating system kernel cannot access. This isolated memory area is initialized and protected during the boot process so that components in the larger operating system environment cannot tamper with it. Credential Guard uses the TPM to protect its keys with TPM measurements, so they are accessible only during the boot process step when the separate region is initialized; they are not available for the normal operating system kernel. The local security authority code in the Windows kernel interacts with the isolated memory area by passing in credentials and receiving single-use authorization tokens in return. +Similar to the way Microsoft Hyper-V keeps virtual machines (VMs) separate from one another, Credential Guard uses virtualization to isolate the process that hashes credentials in a memory area that the operating system kernel can't access. This isolated memory area is initialized and protected during the boot process so that components in the larger operating system environment can't tamper with it. Credential Guard uses the TPM to protect its keys with TPM measurements, so they are accessible only during the boot process step when the separate region is initialized; they are not available for the normal operating system kernel. The local security authority code in the Windows kernel interacts with the isolated memory area by passing in credentials and receiving single-use authorization tokens in return. -The resulting solution provides defense in depth, because even if malware runs in the operating system kernel, it cannot access the secrets inside the isolated memory area that actually generates authorization tokens. The solution does not solve the problem of key loggers because the passwords such loggers capture actually pass through the normal Windows kernel, but when combined with other solutions, such as smart cards for authentication, Credential Guard greatly enhances the protection of credentials in Windows. +The resulting solution provides defense in depth, because even if malware runs in the operating system kernel, it can't access the secrets inside the isolated memory area that actually generates authorization tokens. The solution does not solve the problem of key loggers because the passwords such loggers capture actually pass through the normal Windows kernel, but when combined with other solutions, such as smart cards for authentication, Credential Guard greatly enhances the protection of credentials in Windows. ## Conclusion @@ -139,9 +139,9 @@ The TPM adds hardware-based security benefits to Windows. When installed on hard |Feature | Benefits when used on a system with a TPM| |---|---| -| Platform Crypto Provider | | +| Platform Crypto Provider | | | Virtual Smart Card | | -| Windows Hello for Business | | +| Windows Hello for Business | | | BitLocker Drive Encryption | | |Device Encryption | | | Measured Boot | | diff --git a/windows/security/information-protection/tpm/initialize-and-configure-ownership-of-the-tpm.md b/windows/security/information-protection/tpm/initialize-and-configure-ownership-of-the-tpm.md index de9ce89cdd..89649c5eed 100644 --- a/windows/security/information-protection/tpm/initialize-and-configure-ownership-of-the-tpm.md +++ b/windows/security/information-protection/tpm/initialize-and-configure-ownership-of-the-tpm.md @@ -1,6 +1,6 @@ --- -title: Troubleshoot the TPM (Windows) -description: This article for the IT professional describes how to view status for, clear, or troubleshoot the Trusted Platform Module (TPM). +title: Troubleshoot the TPM +description: Learn how to view and troubleshoot the Trusted Platform Module (TPM). ms.prod: windows-client author: paolomatarazzo ms.author: paoloma @@ -18,45 +18,41 @@ ms.collection: # Troubleshoot the TPM -This article provides information for the IT professional to troubleshoot the Trusted Platform Module (TPM): +This article provides information how to troubleshoot the Trusted Platform Module (TPM): -- [Troubleshoot TPM initialization](#troubleshoot-tpm-initialization) -- [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm) +- [Troubleshoot TPM initialization](#troubleshoot-tpm-initialization) +- [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm) With TPM 1.2 and Windows 11, you can also take the following actions: -- [Turn on or turn off the TPM](#turn-on-or-turn-off) +- [Turn on or turn off the TPM](#turn-on-or-turn-off) For information about the TPM cmdlets, see [TPM Cmdlets in Windows PowerShell](/powershell/module/trustedplatformmodule/?view=win10-ps&preserve-view=true). ## About TPM initialization and ownership -Starting with Windows 10 and Windows 11, the operating system automatically initializes and takes ownership of the TPM. This is a change from previous operating systems, where you would initialize the TPM and create an owner password. +Windows automatically initializes and takes ownership of the TPM. This is a change from previous operating systems, where you had to initialize the TPM and create an owner password. -## Troubleshoot TPM initialization +### TPM initialization If you find that Windows isn't able to initialize the TPM automatically, review the following information: -- You can try clearing the TPM to the factory default values and allowing Windows to re-initialize it. For important precautions for this process, and instructions for completing it, see [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm), later in this article. +- You can try clearing the TPM to the factory default values, allowing Windows to reinitialize it. For important precautions for this process, and instructions for completing it, see [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm) +- If the TPM is a TPM 2.0 and isn't detected by Windows, verify that your computer hardware contains a Unified Extensible Firmware Interface (UEFI) that is Trusted Computing Group-compliant. Also, ensure that in the UEFI settings, the TPM hasn't been disabled or hidden from the operating system +- If you have TPM 1.2 with Windows 11, the TPM might be turned off, and need to be turned back on, as described in [Turn on the TPM](#turn-on-the-tpm). When it's turned back on, Windows will reinitialize it +- If you're attempting to set up BitLocker with the TPM, check which TPM driver is installed on the computer. We recommend always using one of the TPM drivers that is provided by Microsoft and is protected with BitLocker. If a non-Microsoft TPM driver is installed, it may prevent the default TPM driver from loading and cause BitLocker to report that a TPM isn't present on the computer. If you have a non-Microsoft driver installed, remove it, and then allow the operating system to initialize the TPM -- If the TPM is a TPM 2.0 and isn't detected by Windows, verify that your computer hardware contains a Unified Extensible Firmware Interface (UEFI) that is Trusted Computing Group-compliant. Also, ensure that in the UEFI settings, the TPM hasn't been disabled or hidden from the operating system. - -- If you have TPM 1.2 with Windows 11, the TPM might be turned off, and need to be turned back on, as described in [Turn on the TPM](#turn-on-the-tpm). When it's turned back on, Windows will re-initialize it. - -- If you're attempting to set up BitLocker with the TPM, check which TPM driver is installed on the computer. We recommend always using one of the TPM drivers that is provided by Microsoft and is protected with BitLocker. If a non-Microsoft TPM driver is installed, it may prevent the default TPM driver from loading and cause BitLocker to report that a TPM isn't present on the computer. If you have a non-Microsoft driver installed, remove it and then allow the operating system to initialize the TPM. - -### Troubleshoot network connection issues for Windows 11 +### Network connection issues for domain-joined Windows 11 devices If you have Windows 11, the initialization of the TPM can't complete when your computer has network connection issues and both of the following conditions exist: -- An administrator has configured your computer to require that TPM recovery information be saved in Active Directory Domain Services (AD DS). This requirement can be configured through Group Policy. +- An administrator has configured your computer to require that TPM recovery information be saved in Active Directory Domain Services (AD DS). This requirement can be configured through group policy +- A domain controller can't be reached. This scenario may occur on a device that is currently disconnected from the internal network, separated from the domain by a firewall, or experiencing a network component failure (such as an unplugged cable or a faulty network adapter) -- A domain controller can't be reached. This can occur on a computer that is currently disconnected from the network, separated from the domain by a firewall, or experiencing a network component failure (such as an unplugged cable or a faulty network adapter). +If these issues occur, an error message appears, and you can't complete the initialization process. To avoid the issue, allow Windows to initialize the TPM while you're connected to the corporate network, and you can contact a domain controller. -If these issues occur, an error message appears, and you can't complete the initialization process. To avoid this issue, allow Windows to initialize the TPM while you're connected to the corporate network and you can contact a domain controller. +### Systems with multiple TPMs -### Troubleshoot systems with multiple TPMs - -Some systems may have multiple TPMs and the active TPM may be toggled in UEFI. Windows does not support this behavior. If you switch TPMs, Windows might not properly detect or interact with the new TPM. If you plan to switch TPMs you should toggle to the new TPM, clear it, and reinstall Windows. For more information, see [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm), later in this article. +Some systems may have multiple TPMs and the active TPM may be toggled in UEFI. Windows doesn't support this configuration. If you switch TPMs, Windows might not properly detect or interact with the new TPM. If you plan to switch TPMs, you should toggle to the new TPM, clear it, and reinstall Windows. For more information, see [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm). For example, toggling TPMs will cause BitLocker to enter recovery mode. We strongly recommend that, on systems with two TPMs, one TPM is selected to be used and the selection isn't changed. @@ -64,7 +60,7 @@ For example, toggling TPMs will cause BitLocker to enter recovery mode. We stron You can use the Windows Defender Security Center app to clear the TPM as a troubleshooting step, or as a final preparation before a clean installation of a new operating system. Preparing for a clean installation in this way helps ensure that the new operating system can fully deploy any TPM-based functionality that it includes, such as attestation. However, even if the TPM isn't cleared before a new operating system is installed, most TPM functionality will probably work correctly. -Clearing the TPM resets it to an unowned state. After you clear the TPM, the Windows operating system will automatically re-initialize it and take ownership again. +Clearing the TPM resets it to an unowned state. After you clear the TPM, the Windows operating system will automatically reinitialize it and take ownership again. > [!WARNING] > Clearing the TPM can result in data loss. For more information, see the next section, "Precautions to take before clearing the TPM." @@ -73,74 +69,49 @@ Clearing the TPM resets it to an unowned state. After you clear the TPM, the Win Clearing the TPM can result in data loss. To protect against such loss, review the following precautions: -- Clearing the TPM causes you to lose all created keys associated with the TPM, and data protected by those keys, such as a virtual smart card or a sign-in PIN. Make sure that you have a backup and recovery method for any data that is protected or encrypted by the TPM. - -- Don't clear the TPM on a device you don't own, such as a work or school PC, without being instructed to do so by your IT administrator. - -- If you want to temporarily suspend TPM operations and you have TPM 1.2 with Windows 10, version 1507 or 1511, or Windows 11, you can turn off the TPM. For more information, see [Turn off the TPM](#turn-off-the-tpm), later in this article. - -- Always use functionality in the operating system (such as TPM.msc) to the clear the TPM. Don't clear the TPM directly from UEFI. - -- Because your TPM security hardware is a physical part of your computer, before clearing the TPM, you might want to read the manuals or instructions that came with your computer, or search the manufacturer's website. +- Clearing the TPM causes you to lose all created keys associated with the TPM, and data protected by those keys, such as a virtual smart card or a sign-in PIN. Make sure that you have a backup and recovery method for any data that is protected or encrypted by the TPM +- Don't clear the TPM on a device you don't own, such as a work or school PC, without being instructed to do so by your IT administrator +- If you want to temporarily suspend TPM operations on Windows 11, you can turn off the TPM. For more information, see [Turn off the TPM](#turn-off-the-tpm) +- Always use functionality in the operating system (such as TPM.msc) to the clear the TPM. Don't clear the TPM directly from UEFI +- Because your TPM security hardware is a physical part of your computer, before clearing the TPM, you might want to read the manuals or instructions that came with your computer, or search the manufacturer's website Membership in the local Administrators group, or equivalent, is the minimum required to complete this procedure. **To clear the TPM** -1. Open the Windows Defender Security Center app. +1. Open the Windows Defender Security Center app +1. Select **Device security** +1. Select **Security processor details** +1. Select **Security processor troubleshooting** +1. Select **Clear TPM**. + - You'll be prompted to restart the computer. During the restart, you might be prompted by the UEFI to press a button to confirm that you wish to clear the TPM. + - After the device restarts, your TPM will be automatically prepared for use by Windows. -2. Select **Device security**. - -3. Select **Security processor details**. - -4. Select **Security processor troubleshooting**. - -5. Select **Clear TPM**. - -6. You will be prompted to restart the computer. During the restart, you might be prompted by the UEFI to press a button to confirm that you wish to clear the TPM. - -7. After the PC restarts, your TPM will be automatically prepared for use by Windows. - -## Turn on or turn off the TPM (available only with TPM 1.2 with Windows 10, version 1507 and higher) +## Turn on or turn off the TPM Normally, the TPM is turned on as part of the TPM initialization process. You don't normally need to turn the TPM on or off. However, if necessary you can do so by using the TPM MMC. ### Turn on the TPM -If you want to use the TPM after you have turned it off, you can use the following procedure to turn on the TPM. +If you want to use the TPM after you've turned it off, you can use the following procedure to turn on the TPM. -**To turn on the TPM (TPM 1.2 with Windows 10, version 1507 and higher)** +1. Open the TPM MMC (tpm.msc) +1. In the **Action** pane, select **Turn TPM On** to display the **Turn on the TPM Security Hardware** page. Read the instructions on this page +1. Select **Shutdown** (or **Restart**), and then follow the UEFI screen prompts -1. Open the TPM MMC (tpm.msc). - -2. In the **Action** pane, select **Turn TPM On** to display the **Turn on the TPM Security Hardware** page. Read the instructions on this page. - -3. Select **Shutdown** (or **Restart**), and then follow the UEFI screen prompts. - - After the computer restarts, but before you sign in to Windows, you will be prompted to accept the reconfiguration of the TPM. This ensures that the user has physical access to the computer and that malicious software isn't attempting to make changes to the TPM. +After the device restarts, but before you sign in to Windows, you'll be prompted to accept the reconfiguration of the TPM. The acceptance ensures that the user has physical access to the computer and that malicious software isn't attempting to make changes to the TPM. ### Turn off the TPM If you want to stop using the services that are provided by the TPM, you can use the TPM MMC to turn off the TPM. -**To turn off the TPM (TPM 1.2 with Windows 10, version 1507 and higher)** - -1. Open the TPM MMC (tpm.msc). - -2. In the **Action** pane, select **Turn TPM Off** to display the **Turn off the TPM security hardware** page. - -3. In the **Turn off the TPM security hardware** dialog box, select a method to enter your owner password and turning off the TPM: - - - If you saved your TPM owner password on a removable storage device, insert it, and then select **I have the owner password file**. In the **Select backup file with the TPM owner password** dialog box, select **Browse** to locate the .tpm file that is saved on your removable storage device, select **Open**, and then select **Turn TPM Off**. - - - If you don't have the removable storage device with your saved TPM owner password, select **I want to enter the password**. In the **Type your TPM owner password** dialog box, type your password (including hyphens), and then select **Turn TPM Off**. - - - If you didn't save your TPM owner password or no longer know it, select **I do not have the TPM owner password**, and follow the instructions that are provided in the dialog box and subsequent UEFI screens to turn off the TPM without entering the password. +1. Open the TPM MMC (`tpm.msc`) +1. In the **Action** pane, select **Turn TPM Off** to display the **Turn off the TPM security hardware** page +1. In the **Turn off the TPM security hardware** dialog box, select a method to enter your owner password and turning off the TPM: + - If you saved your TPM owner password on a removable storage device, insert it, and then select **I have the owner password file**. In the **Select backup file with the TPM owner password** dialog box, select **Browse** to locate the *.tpm* file that is saved on your removable storage device, select **Open**, and then select **Turn TPM Off** + - If you don't have the removable storage device with your saved TPM owner password, select **I want to enter the password**. In the **Type your TPM owner password** dialog box, type your password (including hyphens), and then select **Turn TPM Off** + - If you didn't save your TPM owner password or no longer know it, select **I do not have the TPM owner password**, and follow the instructions that are provided in the dialog box and subsequent UEFI screens to turn off the TPM without entering the password ## Use the TPM cmdlets You can manage the TPM using Windows PowerShell. For details, see [TPM Cmdlets in Windows PowerShell](/powershell/module/trustedplatformmodule/?view=win10-ps&preserve-view=true). - -## Related articles - -- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of articles) diff --git a/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md b/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md index adcf3d0a31..de49d856c6 100644 --- a/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md +++ b/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md @@ -1,6 +1,6 @@ --- -title: Understanding PCR banks on TPM 2.0 devices (Windows) -description: This topic for the IT professional provides background about what happens when you switch PCR banks on TPM 2.0 devices. +title: UnderstandPCR banks on TPM 2.0 devices +description: Learn about what happens when you switch PCR banks on TPM 2.0 devices. ms.prod: windows-client author: paolomatarazzo ms.author: paoloma @@ -13,55 +13,51 @@ appliesto: - ✅ Windows Server 2016 and later --- -# Understanding PCR banks on TPM 2.0 devices +# PCR banks on TPM 2.0 devices -For steps on how to switch PCR banks on TPM 2.0 devices on your PC, you should contact your OEM or UEFI vendor. This topic provides background about what happens when you switch PCR banks on TPM 2.0 devices. +For steps on how to switch PCR banks on TPM 2.0 devices on your PC, you should contact your OEM or UEFI vendor. This article provides background about what happens when you switch PCR banks on TPM 2.0 devices. -A Platform Configuration Register (PCR) is a memory location in the TPM that has some unique properties. The size of the value that can be stored in a PCR is determined by the size of a digest generated by an associated hashing algorithm. A SHA-1 PCR can store 20 bytes – the size of a SHA-1 digest. Multiple PCRs associated with the same hashing algorithm are referred to as a PCR bank. +A *Platform Configuration Register (PCR)* is a memory location in the TPM that has some unique properties. The size of the value that can be stored in a PCR is determined by the size of a digest generated by an associated hashing algorithm. A SHA-1 PCR can store 20 bytes - the size of a SHA-1 digest. Multiple PCRs associated with the same hashing algorithm are referred to as a *PCR bank*. -To store a new value in a PCR, the existing value is extended with a new value as follows: -PCR\[N\] = HASHalg( PCR\[N\] || ArgumentOfExtend ) +To store a new value in a PCR, the existing value is extended with a new value as follows: `PCR[N] = HASHalg( PCR[N] || ArgumentOfExtend)` -The existing value is concatenated with the argument of the TPM Extend operation. The resulting concatenation is then used as input to the associated hashing algorithm, which computes a digest of the input. This computed digest becomes the new value of the PCR. +The existing value is concatenated with the argument of the TPM Extend operation. The resulting concatenation is then used as input to the associated hashing algorithm, which computes a digest of the input. The computed digest becomes the new value of the PCR. -The [TCG PC Client Platform TPM Profile Specification](http://www.trustedcomputinggroup.org/pc-client-platform-tpm-profile-ptp-specification/) defines the inclusion of at least one PCR bank with 24 registers. The only way to reset the first 16 PCRs is to reset the TPM itself. This restriction helps ensure that the value of those PCRs can only be modified via the TPM Extend operation. +The [TCG PC Client Platform TPM Profile Specification](http://www.trustedcomputinggroup.org/pc-client-platform-tpm-profile-ptp-specification/) defines the inclusion of at least one PCR bank with 24 registers. The only way to reset the first 16 PCRs is to reset the TPM itself. This restriction helps to ensure that the value of those PCRs can only be modified via the TPM Extend operation. -Some TPM PCRs are used as checksums of log events. The log events are extended in the TPM as the events occur. Later, an auditor can validate the logs by computing the expected PCR values from the log and comparing them to the PCR values of the TPM. Since the first 16 TPM PCRs cannot be modified arbitrarily, a match between an expected PCR value in that range and the actual TPM PCR value provides assurance of an unmodified log. +Some TPM PCRs are used as checksums of log events. The log events are extended in the TPM as the events occur. Later, an auditor can validate the logs by computing the expected PCR values from the log and comparing them to the PCR values of the TPM. Since the first 16 TPM PCRs can't be modified arbitrarily, a match between an expected PCR value in that range and the actual TPM PCR value provides assurance of an unmodified log. ## How does Windows use PCRs? -To bind the use of a TPM based key to a certain state of the PC, the key can be sealed to an expected set of PCR values. For instance, PCRs 0 through 7 have a well-defined value after the boot process – when the OS is loaded. When the hardware, firmware, or boot loader of the machine changes, the change can be detected in the PCR values. Windows uses this capability to make certain cryptographic keys only available at certain times during the boot process. For instance, the BitLocker key can be used at a certain point in the boot, but not before or after. +To bind the use of a TPM based key to a certain state of the device, the key can be sealed to an expected set of PCR values.\ +For instance, PCRs 0 through 7 have a well-defined value after the boot process, when the OS is loaded. When the hardware, firmware, or boot loader of the machine changes, the change can be detected in the PCR values. Windows uses this capability to make certain cryptographic keys only available at certain times during the boot process. For instance, the BitLocker key can be used at a certain point in the boot, but not before or after. -It is important to note that this binding to PCR values also includes the hashing algorithm used for the PCR. For instance, a key can be bound to a specific value of the SHA-1 PCR\[12\], if using the SHA-256 PCR bank, even with the same system configuration. Otherwise, the PCR values will not match. +It's important to note that this binding to PCR values also includes the hashing algorithm used for the PCR. For instance, a key can be bound to a specific value of the `SHA-1 PCR[12]`, if using the SHA-256 PCR bank, even with the same system configuration. Otherwise, the PCR values won't match. ## What happens when PCR banks are switched? When the PCR banks are switched, the algorithm used to compute the hashed values stored in the PCRs during extend operations is changed. Each hash algorithm will return a different cryptographic signature for the same inputs. -As a result, if the currently used PCR bank is switched all keys that have been bound to the previous PCR values will no longer work. For example, if you had a key bound to the SHA-1 value of PCR\[12\] and subsequently changed the PCR bank to SHA-256, the banks wouldn't match, and you would be unable to use that key. The BitLocker key is secured using the PCR banks and Windows will not be able to unseal it if the PCR banks are switched while BitLocker is enabled. +As a result, if the currently used PCR bank is switched all keys that have been bound to the previous PCR values will no longer work. For example, if you had a key bound to the SHA-1 value of PCR\[12\] and subsequently changed the PCR bank to SHA-256, the banks wouldn't match, and you would be unable to use that key. The BitLocker key is secured using the PCR banks and Windows won't be able to unseal it if the PCR banks are switched while BitLocker is enabled. ## What can I do to switch PCRs when BitLocker is already active? -Before switching PCR banks you should suspend or disable BitLocker – or have your recovery key ready. For steps on how to switch PCR banks on your PC, you should contact your OEM or UEFI vendor. +Before switching PCR banks, you should suspend or disable BitLocker or have the recovery key ready. For steps on how to switch PCR banks on your PC, contact your OEM or UEFI vendor. ## How can I identify which PCR bank is being used? -A TPM can be configured to have multiple PCR banks active. When BIOS is performing measurements it will do so into all active PCR banks, depending on its capability to make these measurements. BIOS may choose to deactivate PCR banks that it does not support or "cap" PCR banks that it does not support by extending a separator. The following registry value identifies which PCR banks are active. +You can configure a TPM to have multiple PCR banks active. When BIOS performs measurements, it does so into all active PCR banks, depending on its capability to make these measurements. BIOS may choose to deactivate PCR banks that it doesn't support or *cap* PCR banks that it doesn't support by extending a separator. The following registry value identifies which PCR banks are active: -- Registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\IntegrityServices
-- DWORD: TPMActivePCRBanks
-- Defines which PCR banks are currently active. (This value should be interpreted as a bitmap for which the bits are defined in the [TCG Algorithm Registry](https://trustedcomputinggroup.org/resource/tcg-algorithm-registry/) Table 21 of Revision 1.27.)
+- Registry key: `HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\IntegrityServices` +- DWORD: `TPMActivePCRBanks` +- Defines which PCR banks are currently active. (This value should be interpreted as a bitmap for which the bits are defined in the [TCG Algorithm Registry](https://trustedcomputinggroup.org/resource/tcg-algorithm-registry/) Table 21 of Revision 1.27.) -Windows checks which PCR banks are active and supported by the BIOS. Windows also checks if the measured boot log supports measurements for all active PCR banks. Windows will prefer the use of the SHA-256 bank for measurements and will fall back to SHA1 PCR bank if one of the pre-conditions is not met. +Windows checks which PCR banks are active and supported by the BIOS. Windows also checks if the measured boot log supports measurements for all active PCR banks. Windows will prefer the use of the SHA-256 bank for measurements and will fall back to SHA1 PCR bank if one of the pre-conditions isn't met. -You can identify which PCR bank is currently used by Windows by looking at the registry. +You can identify which PCR bank is currently used by Windows by looking at the registry: -- Registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\IntegrityServices
-- DWORD: TPMDigestAlgID
-- Algorithm ID of the PCR bank that Windows is currently using. (This value represents an algorithm identifier as defined in the [TCG Algorithm Registry](https://trustedcomputinggroup.org/resource/tcg-algorithm-registry/) Table 3 of Revision 1.27.)
+- Registry key: `HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\IntegrityServices` +- DWORD: `TPMDigestAlgID` +- Algorithm ID of the PCR bank that Windows is currently using. (This value represents an algorithm identifier as defined in the [TCG Algorithm Registry](https://trustedcomputinggroup.org/resource/tcg-algorithm-registry/) Table 3 of Revision 1.27.) -Windows only uses one PCR bank to continue boot measurements. All other active PCR banks will be extended with a separator to indicate that they are not used by Windows and measurements that appear to be from Windows should not be trusted. - -## Related topics - -- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics) +Windows only uses one PCR bank to continue boot measurements. All other active PCR banks will be extended with a separator to indicate that they aren't used by Windows and measurements that appear to be from Windows shouldn't be trusted.