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---
title: Back up the TPM recovery information to AD DS (Windows 10)
description: This topic for the IT professional describes backup of Trusted Platform Module (TPM) information.
ms.assetid: 62bcec80-96a1-464e-8b3f-d177a7565ac5
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 04/19/2017
---
# Back up the TPM recovery information to AD DS
**Applies to**
- Windows 10, version 1511
- Windows 10, version 1507
**Does not apply to**
- Windows 10, version 1607 or later
With Windows 10, versions 1511 and 1507, 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](https://technet.microsoft.com/library/dn466534(v=ws.11).aspx).
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)
- [TPM Group Policy settings](trusted-platform-module-services-group-policy-settings.md)

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---
title: Change the TPM owner password (Windows 10)
description: This topic for the IT professional describes how to change the password or PIN for the owner of the Trusted Platform Module (TPM) that is installed on your system.
ms.assetid: e43dcff3-acb4-4a92-8816-d6b64b7f2f45
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 04/19/2017
---
# Change the TPM owner password
**Applies to**
- Windows 10, version 1511
- Windows 10, version 1507
This topic for the IT professional describes how to change the password or PIN for the owner of the Trusted Platform Module (TPM) that is installed on your system.
## About the TPM owner password
Starting with Windows 10, version 1607, Windows will not retain the TPM owner password when provisioning the TPM. The password will be set to a random high entropy value and then discarded.
> [!IMPORTANT]
> Although the TPM owner password is not retained starting with Windows 10, version 1607, you can change a default registry key to retain it. However, we strongly recommend that you do not make this change. To retain the TPM owner password, set the registry key 'HKLM\\Software\\Policies\\Microsoft\\TPM' \[REG\_DWORD\] 'OSManagedAuthLevel' to 4. The default value for this key is 2, and unless it is changed to 4 before the TPM is provisioned, the owner password will not be saved.
Only one owner password exists for each TPM. The TPM owner password allows the ability to enable, disable, or clear the TPM without having physical access to the computer, for example, by using the command-line tools remotely. The TPM owner password also allows manipulation of the TPM dictionary attack logic. Taking ownership of the TPM is performed by Windows as part of the provisioning process on each boot. Ownership can change when you share the password or clear your ownership of the TPM so someone else can initialize it.
Without the owner password you can still perform all the preceding actions by means of a physical presence confirmation from UEFI.
### Other TPM management options
Instead of changing your owner password, you can also use the following options to manage your TPM:
- **Clear the TPM**   If you want to invalidate all of the existing keys that have been created since you took ownership of the TPM, you can clear it. For important precautions for this process, and instructions for completing it, see [Clear all the keys from the TPM](initialize-and-configure-ownership-of-the-tpm.md#clear-all-the-keys-from-the-tpm).
- **Turn off the TPM**   With TPM 1.2 and Windows 10, versions 1507 and 1511, you can turn off the TPM. Do this if you want to keep all existing keys and data intact and disable the services that are provided by the TPM. For more info, see [Turn off the TPM](initialize-and-configure-ownership-of-the-tpm.md#turn-off-the-tpm).
## Change the TPM owner password
With Windows 10, version 1507 or 1511, if you have opted specifically to preserve the TPM owner password, you can use the saved password to change to a new password.
To change to a new TPM owner password, in TPM.msc, click **Change Owner Password**, and follow the instructions. You will be prompted to provide the owner password file or to type the password. Then you can create a new password, either automatically or manually, and save the password in a file or as a printout.
## Use the TPM cmdlets
You can manage the TPM using Windows PowerShell. For details, see [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx).
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)

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---
title: How Windows uses the TPM
description: This topic for the IT professional describes the Trusted Platform Module (TPM) and how Windows uses it to enhance security.
ms.assetid: 0f7e779c-bd25-42a8-b8c1-69dfb54d0c7f
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
localizationpriority: high
author: brianlic-msft
ms.date: 10/27/2017
---
# How Windows 10 uses the Trusted Platform Module
The Windows 10 operating system improves most existing security features in the operating system and adds groundbreaking new security features such as Device Guard and Windows Hello for Business. It places hardware-based security deeper inside the operating system than previous Windows versions had done, maximizing platform security while increasing usability. To achieve many of these security enhancements, Windows 10 makes extensive use of the Trusted Platform Module (TPM). This article offers a brief overview of the TPM, describes how it works, and discusses the benefits that TPM brings to Windows 10—as well as the cumulative security impact of running Windows 10 on a PC that contains a TPM.
**See also:**
- [Windows 10 Specifications](https://www.microsoft.com/windows/windows-10-specifications)
- [TPM Fundamentals](tpm-fundamentals.md)
- [TPM Recommendations](tpm-recommendations.md) 
## TPM Overview
The TPM is a cryptographic module that enhances computer security and privacy. Protecting data through encryption and decryption, protecting authentication credentials, and proving which software is running on a system are basic functionalities associated with computer security. The TPM helps with all these scenarios and more.
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 10 automatically provisions a TPM, but if the user reinstalls the operating system, he or she may need to tell the operating system to explicitly provision the TPM again 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).
OEMs implement the TPM as a component in a trusted computing platform, such as a PC, tablet, or phone. Trusted computing platforms use the TPM to support privacy and security scenarios that software alone cannot achieve. For example, software alone cannot reliably report whether malware is present during the system startup process. The close integration between TPM and platform increases the transparency of the startup process and supports evaluating device health by enabling reliable measuring and reporting of the software that starts the device. Implementation of a TPM as part of a trusted computing platform provides a hardware root of trust—that is, it behaves in a trusted way. For example, if a key stored in a TPM has properties that disallow exporting the key, that key *truly cannot leave the TPM*.
The TCG designed the TPM as a low-cost, mass-market security solution that addresses the requirements of different customer segments. There are variations in the security properties of different TPM implementations just as there are variations in customer and regulatory requirements for different sectors. In public-sector procurement, for example, some governments have clearly defined security requirements for TPMs, whereas others do not.
Certification programs for TPMs—and technology in general—continue to evolve as the speed of innovation increases. Although having a TPM is clearly better than not having a TPM, Microsoft’s best advice is to determine your organization’s security needs and research any regulatory requirements associated with procurement for your industry. The result is a balance between scenarios used, assurance level, cost, convenience, and availability.
## TPM in Windows 10
The security features of Windows 10 combined with the benefits of a TPM offer practical security and privacy benefits. The following sections start with major TPM-related security features in Windows 10 and go on to describe how key technologies use the TPM to enable or increase security.
## Platform Crypto Provider
Windows includes a cryptography framework called *Cryptographic API: Next Generation* (CNG), the basic approach of which is to implement cryptographic algorithms in different ways but with a common application programming interface (API). Applications that use cryptography can use the common API without knowing the details of how an algorithm is implemented much less the algorithm itself.
Although CNG sounds like a mundane starting point, it illustrates some of the advantages that a TPM provides. Underneath the CNG interface, Windows or third parties supply a cryptographic provider (that is, an implementation of an algorithm) implemented as software libraries alone or in a combination of software and available system hardware or third-party hardware. If implemented through hardware, the cryptographic provider communicates with the hardware behind the software interface of CNG.
The Platform Crypto Provider, introduced in the Windows 8 operating system, exposes the following special TPM properties, which software-only CNG providers cannot offer or cannot offer as effectively:
• **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 are vulnerable to malware. The Platform Crypto Provider can also configure keys that a TPM protects so that they are not 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 is not a source for making additional 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.
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 10 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 simply 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.
## Virtual Smart Card
Smart cards are highly secure physical devices that typically store a single certificate and the corresponding private key. Users insert a smart card into a built-in or USB card reader and enter a PIN to unlock it. Windows can then access the card’s certificate and use the private key for authentication or to unlock BitLocker protected data volumes. Smart cards are popular because they provide two-factor authentication that requires both something the user has (that is, the smart card) and something the user knows (such as the smart card PIN). Smart cards are difficult to use, however, because they require purchase and deployment of both smart cards and smart card readers.
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. Although 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 because it eliminates “lost card” and “card left at home” scenarios while still delivering the benefits of smart card–based multifactor authentication. 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
Windows Hello for Business provides authentication methods intended to replace passwords, which can be difficult to remember and easily compromised. In addition, user name - password solutions for authentication often reuse the same user name – password combinations on multiple devices and services; if those credentials are compromised, they are compromised in many places. Windows Hello for Business provisions devices one by one and combines the information provisioned on each device (i.e., the cryptographic key) with additional information to authenticate users. On a system that has a TPM, the TPM can protect the key. If a system does not have a TPM, software-based techniques protect the key. The additional information the user supplies can be a PIN value or, if the system has the necessary hardware, biometric information, such as fingerprint or facial recognition. To protect privacy, the biometric information is used only on the provisioned device to access the provisioned key: it is not shared across devices.
The adoption of new authentication technology requires that identity providers and organizations deploy and use that technology. Windows Hello for Business lets users authenticate with their existing Microsoft account, an Active Directory account, a Microsoft Azure Active Directory account, or even non-Microsoft Identity Provider Services or Relying Party Services that support [Fast ID Online V2.0 authentication](http://go.microsoft.com/fwlink/p/?LinkId=533889).
Identity providers have flexibility in how they provision credentials on client devices. For example, an organization might provision only those devices that have a TPM so that the organization knows that a TPM protects the credentials. The ability to distinguish a TPM from malware acting like a TPM requires the following TPM capabilities (see Figure 1):
• **Endorsement key**. The TPM manufacturer can create a special key in the TPM called an *endorsement key*. An endorsement key certificate, signed by the manufacturer, says that the endorsement key is present in a TPM that that manufacturer made. Solutions can use the certificate with the TPM containing the endorsement key to confirm a scenario really involves a TPM from a specific TPM manufacturer (instead of malware acting like a TPM.
• **Attestation identity key**. To protect privacy, most TPM scenarios do not directly use an actual endorsement key. Instead, they use attestation identity keys, and an identity certificate authority (CA) uses the endorsement key and its certificate to prove that one or more attestation identity keys actually exist in a real TPM. The identity CA issues attestation identity key certificates. More than one identity CA will generally see the same endorsement key certificate that can uniquely identify the TPM, but any number of attestation identity key certificates can be created to limit the information shared in other scenarios.
![TPM Capabilities](images/tpm-capabilities.png)
*Figure 1: TPM Cryptographic Key Management*
For Windows Hello for Business, Microsoft can fill the role of the identity CA. Microsoft services can issue an attestation identity key certificate for each device, user, and identify provider to ensure that privacy is protected and to help identity providers ensure that device TPM requirements are met before Windows Hello for Business credentials are provisioned.
## BitLocker Drive Encryption
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 additional 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:
• **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.
• **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).
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.
Newer hardware and Windows 10 work better together to disable direct memory access through ports and reduce attack vectors. The result is that organizations can deploy more systems without requiring users to enter additional authorization information during the startup process. The right hardware allows BitLocker to be used with the “TPM-only” configuration giving users a single sign-on experience without having to enter a PIN or USB key during boot.
## Device Encryption
Device Encryption is the consumer version of BitLocker, and it uses the same underlying technology. How it works is if a customer logs on with a Microsoft account and the system meets Modern Standby hardware requirements, BitLocker Drive Encryption is enabled automatically in Windows 10. The recovery key is backed up in the Microsoft cloud and is accessible to the consumer through his or her Microsoft account. The Modern Standby hardware requirements inform Windows 10 that the hardware is appropriate for deploying Device Encryption and allows use of the “TPM-only” configuration for a simple consumer experience. In addition, Modern Standby hardware is designed to reduce the likelihood that measurement values change and prompt the customer for the recovery key.
For software measurements, Device Encryption relies on measurements of the authority providing software components (based on code signing from manufacturers such as OEMs or Microsoft) instead of the precise hashes of the software components themselves. This permits servicing of components without changing the resulting measurement values. For configuration measurements, the values used are based on the boot security policy instead of the numerous other configuration settings recorded during startup. These values also change less frequently. The result is that Device Encryption is enabled on appropriate hardware in a user-friendly way while also protecting data.
## Measured Boot
Windows 8 introduced Measured Boot as a way for the operating system to record the chain of measurements of software components and configuration information in the TPM through the initialization of the Windows operating system. In previous Windows versions, the measurement chain stopped at the Windows Boot Manager component itself, and the measurements in the TPM were not helpful for understanding the starting state of Windows.
The Windows boot process happens in stages and often involves third-party drivers to communicate with vendor-specific hardware or implement antimalware solutions. For software, Measured Boot records measurements of the Windows kernel, Early-Launch Anti-Malware drivers, and boot drivers in the TPM. For configuration settings, Measured Boot records security-relevant information such as signature data that antimalware drivers use and configuration data about Windows security features (e.g., whether BitLocker is on or off).
Measured Boot ensures that TPM measurements fully reflect the starting state of Windows software and configuration settings. If security settings and other protections are set up correctly, they can be trusted to maintain the security of the running operating system thereafter. Other scenarios can use the operating system’s starting state to determine whether the running operating system should be trusted.
TPM measurements are designed to avoid recording any privacy-sensitive information as a measurement. As an additional privacy protection, Measured Boot stops the measurement chain at the initial starting state of Windows. Therefore, the set of measurements does not include details about which applications are in use or how Windows is being used. Measurement information can be shared with external entities to show that the device is enforcing adequate security policies and did not start with malware.
The TPM provides the following way for scenarios to use the measurements recorded in the TPM during boot:
• **Remote Attestation**. Using an attestation identity key, the TPM can generate and cryptographically sign a statement (or*quote*) of the current measurements in the TPM. Windows 10 can create unique attestation identity keys for various scenarios to prevent separate evaluators from collaborating to track the same device. Additional information in the quote is cryptographically scrambled to limit information sharing and better protect privacy. By sending the quote to a remote entity, a device can attest which software and configuration settings were used to boot the device and initialize the operating system. An attestation identity key certificate can provide further assurance that the quote is coming from a real TPM. Remote attestation is the process of recording measurements in the TPM, generating a quote, and sending the quote information to another system that evaluates the measurements to establish trust in a device. Figure 2 illustrates this process.
When new security features are added to Windows, Measured Boot adds security-relevant configuration information to the measurements recorded in the TPM. Measured Boot enables remote attestation scenarios that reflect the system firmware and the Windows initialization state.
![Process to Create Evidence of Boot Software and Configuration Using TPM](images/process-to-create-evidence-of-boot-software-and-configuration-using-tpm.png)
*Figure 2: Process used to create evidence of boot software and configuration using a TPM*
## Health Attestation
Some Windows 10 improvements help security solutions implement remote attestation scenarios. Microsoft provides a Health Attestation service, which can create attestation identity key certificates for TPMs from different manufacturers as well as parse measured boot information to extract simple security assertions, such as whether BitLocker is on or off. The simple security assertions can be used to evaluate device health.
Mobile device management (MDM) solutions can receive simple security assertions from the Microsoft Health Attestation service for a client without having to deal with the complexity of the quote or the detailed TPM measurements. MDM solutions can act on the security information by quarantining unhealthy devices or blocking access to cloud services such as Microsoft Office 365.
## Credential Guard
Credential Guard is a new feature in Windows 10 that helps protect Windows credentials in organizations that have deployed AD DS. Historically, a user’s credentials (e.g., 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.
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 10.
## Conclusion
The TPM adds hardware-based security benefits to Windows 10. When installed on hardware that includes a TPM, Window 10 delivers remarkably improved security benefits. The following table summarizes the key benefits of the TPM’s major features.
|Feature | Benefits when used on a system with a TPM|
|---|---|
| Platform Crypto Provider | • &nbsp; &nbsp; If the machine is compromised, the private key associated with the certificate cannot be copied off the device.<br />• &nbsp; &nbsp; The TPM’s dictionary attack mechanism protects PIN values to use a certificate.
| Virtual Smart Card | • &nbsp; &nbsp; Achieve security similar to that of physical smart cards without deploying physical smart cards or card readers.|
| Windows Hello for Business | • &nbsp; &nbsp; Credentials provisioned on a device cannot be copied elsewhere. <br /> • &nbsp; &nbsp; Confirm a device’s TPM before credentials are provisioned. |
| BitLocker Drive Encryption | • &nbsp; &nbsp; Multiple options are available for enterprises to protect data at rest while balancing security requirements with different device hardware.
|Device Encryption | • &nbsp; &nbsp; With a Microsoft account and the right hardware, consumers’ devices seamlessly benefit from data-at-rest protection.
| Measured Boot | • &nbsp; &nbsp; A hardware root of trust contains boot measurements that help detect malware during remote attestation.
| Health Attestation | • &nbsp; &nbsp; MDM solutions can easily perform remote attestation and evaluate client health before granting access to resources or cloud services such as Office 365.
| Credential Guard | • &nbsp; &nbsp; Defense in depth increases so that even if malware has administrative rights on one machine, it is significantly more difficult to compromise additional machines in an organization.
<br />
Although some of the aforementioned features have additional hardware requirements (e.g., virtualization support), the TPM is a cornerstone of Windows 10 security. Microsoft and other industry stakeholders continue to improve the global standards associated with TPM and find more and more applications that use it to provide tangible benefits to customers. Microsoft has included support for most TPM features in its version of Windows for the Internet of Things (IoT) called [Windows 10 IoT Core](https://developer.microsoft.com/windows/iot/iotcore). IoT devices that might be deployed in insecure physical locations and connected to cloud services like [Azure IoT Hub](https://azure.microsoft.com/documentation/services/iot-hub/) for management can use the TPM in innovative ways to address their emerging security requirements.

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---
title: View status, clear, or troubleshoot the TPM (Windows 10)
description: This topic for the IT professional describes how to view status for, clear, or troubleshoot the Trusted Platform Module (TPM).
ms.assetid: 1166efaf-7aa3-4420-9279-435d9c6ac6f8
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 04/19/2017
---
# View status, clear, or troubleshoot the TPM
**Applies to**
- Windows 10
- Windows Server 2016
This topic for the IT professional describes actions you can take through the Trusted Platform Module (TPM) snap-in, **TPM.msc**:
- [View the status of the TPM](#view-the-status-of-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 10, version 1507 or 1511, you can also take the following actions:
- [Turn on or turn off the TPM](#turn-on-or-turn-off)
For information about the TPM cmdlets, see [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx).
## About TPM initialization and ownership
Starting with Windows 10, 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. Therefore, with Windows 10, in most cases, we recommend that you avoid configuring the TPM through **TPM.msc**. The one exception is that in certain circumstances you might use **TPM.msc** to clear the TPM. For more information, see [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm), later in this topic.
## View the status of the TPM
To view the status of the TPM, open the TPM Management console (TPM.msc). In the center pane, find the **Status** box.
In most cases, the status will be **Ready**. If the status is ready but “**with reduced functionality**,” see [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm), later in this topic.
If the status is **Not ready**, you can try the steps in [Clear all the keys from the TPM](#clear-all-the-keys-from-the-tpm), later in this topic. If this does not bring it to a **Ready** state, contact the manufacturer, and see the troubleshooting suggestions in the next section.
## Troubleshoot TPM initialization
If you find that Windows is not 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 topic.
- If the TPM is a TPM 2.0 and is not 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 has not been disabled or hidden from the operating system.
- If you have TPM 1.2 with Windows 10, version 1507 or 1511, 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 is turned back on, Windows will re-initialize it.
- If you are 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 is not 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 10, versions 1507 and 1511
If you have Windows 10, version 1507 or 1511, the initialization of the TPM cannot 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.
- A domain controller cannot 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 cannot complete the initialization process. To avoid this issue, allow Windows to initialize the TPM while you are connected to the corporate network and you can contact a domain controller.
### Troubleshoot systems with multiple TPMs
Some systems may have multiple TPMs and the active TPM may be toggled in UEFI. Windows 10 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 topic.
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 is not changed.
## Clear all the keys from the TPM
With Windows 10, in most cases, we recommend that you avoid configuring the TPM through TPM.msc. The one exception is that you can use TPM.msc to clear the TPM, for example, 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, for example, attestation. However, even if the TPM is not 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 10 operating system will automatically re-initialize 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.”
There are several ways to clear the TPM:
- **Clear the TPM as part of a complete reset of the computer**: You might want to remove all files from the computer and completely reset it, for example, in preparation for a clean installation. To do this, we recommend that you use the **Reset** option in **Settings**. When you perform a reset and use the **Remove everything** option, it will clear the TPM as part of the reset. You might be prompted to press a key before the TPM can be cleared. For more information, see the “Reset this PC” section in [Recovery options in Windows 10](https://support.microsoft.com/en-us/help/12415/windows-10-recovery-options).
- **Clear the TPM to fix “reduced functionality” or “Not ready” TPM status**: If you open TPM.msc and see that the TPM status is something other than **Ready**, you can can try using TPM.msc to clear the TPM and fix the status. However, be sure to review the precautions in the next section.
### Precautions to take before clearing the TPM
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 login PIN. Make sure that you have a backup and recovery method for any data that is protected or encrypted by the TPM.
- Do not clear the TPM on a device you do not 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, you can turn off the TPM. For more information, see [Turn off the TPM](#turn-off-the-tpm), later in this topic.
- Always use functionality in the operating system (such as TPM.msc) to the clear the TPM. Do not 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 TPM MMC (tpm.msc).
2. If the **User Account Control** dialog box appears, confirm that the action it displays is what you want, and then click **Yes**.
3. Under **Actions**, click **Clear TPM**.
4. 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.
5. After the PC restarts, your TPM will be automatically prepared for use by Windows 10.
## <a href="" id="turn-on-or-turn-off"></a>Turn on or turn off the TPM (available only with TPM 1.2 with Windows 10, version 1507 or 1511)
Normally, the TPM is turned on as part of the TPM initialization process. You do not 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.
**To turn on the TPM (TPM 1.2 with Windows 10, version 1507 or 1511 only)**
1. Open the TPM MMC (tpm.msc).
2. In the **Action** pane, click **Turn TPM On** to display the **Turn on the TPM Security Hardware** page. Read the instructions on this page.
3. Click **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 is not 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 or 1511 only)**
1. Open the TPM MMC (tpm.msc).
2. In the **Action** pane, click **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 click **I have the owner password file**. In the **Select backup file with the TPM owner password** dialog box, click **Browse** to locate the .tpm file that is saved on your removable storage device, click **Open**, and then click **Turn TPM Off**.
- If you do not have the removable storage device with your saved TPM owner password, click **I want to enter the password**. In the **Type your TPM owner password** dialog box, type your password (including hyphens), and then click **Turn TPM Off**.
- If you did not save your TPM owner password or no longer know it, click **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.
### Change the TPM Owner Password (available only with Windows 10, version 1607 and earlier versions)
If you have the [owner password](https://technet.microsoft.com/itpro/windows/keep-secure/change-the-tpm-owner-password) available, you can use TPM.msc to change the TPM Owner Password.
1. Open the TPM MMC (tpm.msc).
2. In the **Action** pane, click **Change the Owner Password**
- If you saved your TPM owner password on a removable storage device, insert it, and then click **I have the owner password file**. In the **Select backup file with the TPM owner password** dialog box, click **Browse** to locate the .tpm file that is saved on your removable storage device, click **Open**, and then click **Turn TPM Off**.
- If you do not have the removable storage device with your saved TPM owner password, click **I want to enter the password**. In the **Type your TPM owner password** dialog box, type your password (including hyphens), and then click **Turn TPM Off**.
This capability was fully removed from TPM.msc in later versions of Windows.
## Use the TPM cmdlets
You can manage the TPM using Windows PowerShell. For details, see [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx).
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)

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---
title: Manage TPM commands (Windows 10)
description: This topic for the IT professional describes how to manage which Trusted Platform Module (TPM) commands are available to domain users and to local users.
ms.assetid: a78e751a-2806-43ae-9c20-2e7ca466b765
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 11/30/2017
---
# Manage TPM commands
**Applies to**
- Windows 10
- Windows Server 2016
This topic for the IT professional describes how to manage which Trusted Platform Module (TPM) commands are available to domain users and to local users.
After a computer user takes ownership of the TPM, the TPM owner can limit which TPM commands can be run by creating a list of blocked TPM commands. The list can be created and applied to all computers in a domain by using Group Policy, or a list can be created for individual computers by using the TPM MMC. Because some hardware vendors might provide additional commands or the Trusted Computing Group may decide to add commands in the future, the TPM MMC also supports the ability to block new commands.
Domain administrators can configure a list of blocked TPM commands by using Group Policy. Local administrators cannot allow TPM commands that are blocked through Group Policy. For more information about this Group Policy setting, see [TPM Group Policy settings](trusted-platform-module-services-group-policy-settings.md#configure-the-list-of-blocked-tpm-commands).
Local administrators can block commands by using the TPM MMC, and commands on the default block list are also blocked unless the Group Policy settings are changed from the default settings.
Two policy settings control the enforcement which allows TPM commands to run. For more information about these policy settings, see [TPM Group Policy settings](trusted-platform-module-services-group-policy-settings.md#ignore-the-default-list-of-blocked-tpm-commands).
The following procedures describe how to manage the TPM command lists. You must be a member of the local Administrators group.
**To block TPM commands by using the Local Group Policy Editor**
1. Open the Local Group Policy Editor (gpedit.msc). If the **User Account Control** dialog box appears, confirm that the action it displays is what you want, and then click **Yes**.
> [!NOTE]
> Administrators with appropriate rights in a domain can configure a Group Policy Object (GPO) that can be applied through Active Directory Domain Services (AD DS).
2. In the console tree, under **Computer Configuration**, expand **Administrative Templates**, and then expand **System**.
3. Under **System**, click **Trusted Platform Module Services**.
4. In the details pane, double-click **Configure the list of blocked TPM commands**.
5. Click **Enabled**, and then click **Show**.
6. For each command that you want to block, click **Add**, enter the command number, and then click **OK**.
> [!NOTE]
> For a list of commands, see links in the [TPM Specification](https://www.trustedcomputinggroup.org/tpm-main-specification/).
7. After you have added numbers for each command that you want to block, click **OK** twice.
8. Close the Local Group Policy Editor.
**To block or allow TPM commands by using the TPM MMC**
1. Open the TPM MMC (tpm.msc)
2. If the **User Account Control** dialog box appears, confirm that the action it displays is what you want, and then click **Yes**.
3. In the console tree, click **Command Management**. A list of TPM commands is displayed.
4. In the list, select a command that you want to block or allow.
5. Under **Actions**, click **Block Selected Command** or **Allow Selected Command** as needed. If **Allow Selected Command** is unavailable, that command is currently blocked by Group Policy.
**To block new commands**
1. Open the TPM MMC (tpm.msc).
If the **User Account Control** dialog box appears, confirm that the action it displays is what you want, and then click **Yes**.
2. In the console tree, click **Command Management**. A list of TPM commands is displayed.
3. In the **Action** pane, click **Block New Command**. The **Block New Command** dialog box is displayed.
4. In the **Command Number** text box, type the number of the new command that you want to block, and then click **OK**. The command number you entered is added to the blocked list.
## Use the TPM cmdlets
You can manage the TPM using Windows PowerShell. For details, see [TrustedPlatformModule PowerShell cmdlets](https://docs.microsoft.com/powershell/module/trustedplatformmodule/?view=win10-ps).
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)

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---
title: Manage TPM lockout (Windows 10)
description: This topic for the IT professional describes how to manage the lockout feature for the Trusted Platform Module (TPM) in Windows.
ms.assetid: bf27adbe-404c-4691-a644-29ec722a3f7b
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 05/02/2017
---
# Manage TPM lockout
**Applies to**
- Windows 10
- Windows Server 2016
This topic for the IT professional describes how to manage the lockout feature for the Trusted Platform Module (TPM) in Windows.
## About TPM lockout
The TPM will lock itself to prevent tampering or malicious attacks. TPM lockout often lasts for a variable amount of time or until the computer is turned off. While the TPM is in lockout mode, it generally returns an error message when it receives commands that require an authorization value. One exception is that the TPM always allows the owner at least one attempt to reset the TPM lockout when it is in lockout mode.
TPM ownership is taken upon first boot by Windows. By default, Windows does not retain the TPM owner password.
In some cases, encryption keys are protected by a TPM by requiring a valid authorization value to access the key. A common example is configuring BitLocker Drive Encryption to use the TPM plus PIN key protector. In this scenario, the user must type the correct PIN during the boot process to access the volume encryption key protected by the TPM. To prevent malicious users or software from discovering authorization values, TPMs implement protection logic. The protection logic is designed to slow or stop responses from the TPM if it detects that an entity might be trying to guess authorization values.
**TPM 1.2**
The industry standards from the Trusted Computing Group (TCG) specify that TPM manufacturers must implement some form of protection logic in TPM 1.2 and TPM 2.0 chips. TPM 1.2 devices implement different protection mechanisms and behavior. In general, the TPM chip takes exponentially longer to respond if incorrect authorization values are sent to the TPM. Some TPM chips may not store failed attempts over time. Other TPM chips may store every failed attempt indefinitely. Therefore, some users may experience increasingly longer delays when they mistype an authorization value that is sent to the TPM. This can prevent them from using the TPM for a period of time.
**TPM 2.0**
TPM 2.0 devices have standardized lockout behavior which is configured by Windows. TPM 2.0 devices have a maximum count threshold and a healing time. Windows configures the maximum count to be 32 and the healing time to be 2 hours. This means that every continuous two hours of powered on operation without an event which increases the counter will cause the counter to decrease by 1.
If your TPM has entered lockout mode or is responding slowly to commands, you can reset the lockout value by using the following procedures. Resetting the TPM lockout requires the TPM owner’s authorization. This value is no longer retained by default starting with Windows 10 version 1607.
## Reset the TPM lockout by using the TPM MMC
> [!NOTE]
> This procedure is only available if you have configured Windows to retain the TPM Owner Password. By default, this password is not available in Windows 10 starting with version 1607.
The following procedure explains the steps to reset the TPM lockout by using the TPM MMC.
**To reset the TPM lockout**
1. Open the TPM MMC (tpm.msc).
2. In the **Action** pane, click **Reset TPM Lockout** to start the Reset TPM Lockout Wizard.
3. Choose one of the following methods to enter the TPM owner password:
- If you saved your TPM owner password to a .tpm file, click **I have the owner password file**, and then type the path to the file, or click **Browse** to navigate to the file location.
- If you want to manually enter your TPM owner password, click **I want to enter the owner password**, and then type the password in the text box provided.
> [!NOTE]
> If you enabled BitLocker and your TPM at the same time, and you printed your BitLocker recovery password when you turned on BitLocker, your TPM owner password may have printed with it.
## Use Group Policy to manage TPM lockout settings
The TPM Group Policy settings in the following list are located at:
**Computer Configuration\\Administrative Templates\\System\\Trusted Platform Module Services\\**
- [Standard User Lockout Duration](trusted-platform-module-services-group-policy-settings.md#standard-user-lockout-duration)
This policy setting allows you to manage the duration in minutes for counting standard user authorization failures for TPM commands that require authorization. An authorization failure occurs each time a user sends a command to the TPM and receives an error message that indicates an authorization failure occurred. Authorization failures that are older than the duration you set are ignored. If the number of TPM commands with an authorization failure within the lockout duration equals a threshold, the user is prevented from sending commands to the TPM that require authorization.
- [Standard User Individual Lockout Threshold](trusted-platform-module-services-group-policy-settings.md#standard-user-individual-lockout-threshold)
This policy setting allows you to manage the maximum number of authorization failures for the TPM for each user. This value is the maximum number of authorization failures that each user can have before the user is not allowed to send commands to the TPM that require authorization. If the number of authorization failures equals the duration that is set for the policy setting, the user is prevented from sending commands to the TPM that require authorization.
- [Standard User Total Lockout Threshold](trusted-platform-module-services-group-policy-settings.md#standard-user-total-lockout-threshold)
This policy setting allows you to manage the maximum number of authorization failures for the TPM for all standard users. If the total number of authorization failures for all users equals the duration that is set for the policy, all users are prevented from sending commands to the TPM that require authorization.
For information about mitigating dictionary attacks that use the lockout settings, see [TPM fundamentals](tpm-fundamentals.md#anti-hammering).
## Use the TPM cmdlets
You can manage the TPM using Windows PowerShell. For details, see [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx).
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)

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---
title: Understanding PCR banks on TPM 2.0 devices (Windows 10)
description: This topic for the IT professional provides background about what happens when you switch PCR banks on TPM 2.0 devices.
ms.assetid: 743FCCCB-99A9-4636-8F48-9ECB3A3D10DE
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 04/19/2017
---
# Understanding PCR banks on TPM 2.0 devices
**Applies to**
- Windows 10
- Windows Server 2016
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.
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 )
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 [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.
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.
## How does Windows 10 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 10 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 SHA-256 PCR banks, even with the same system configuration. Otherwise, the PCR values will not 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. For the same input, 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 banks 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 10 will not 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.
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)

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---
title: TPM fundamentals (Windows 10)
description: This topic for the IT professional provides a description of the components of the Trusted Platform Module (TPM 1.2 and TPM 2.0) and explains how they are used to mitigate dictionary attacks.
ms.assetid: ac90f5f9-9a15-4e87-b00d-4adcf2ec3000
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 08/16/2017
---
# TPM fundamentals
**Applies to**
- Windows 10
- Windows Server 2016
This topic for the IT professional provides a description of the components of the Trusted Platform Module (TPM 1.2 and TPM 2.0) and explains how they are used to mitigate dictionary attacks.
A Trusted Platform Module (TPM) is a microchip designed to provide basic security-related functions, primarily involving encryption keys. The TPM is usually installed on the motherboard of a computer, and it communicates with the remainder of the system by using a hardware bus.
Computers that incorporate a TPM can create cryptographic keys and encrypt them so that they can only be decrypted by the TPM. This process, often called wrapping or binding a key, can help protect the key from disclosure. Each TPM has a master wrapping key, called the storage root key, which is stored within the TPM itself. The private portion of a storage root key or endorsement key that is created in a TPM is never exposed to any other component, software, process, or user.
You can specify whether encryption keys that are created by the TPM can be migrated or not. If you specify that they can be migrated, the public and private portions of the key can be exposed to other components, software, processes, or users. If you specify that encryption keys cannot be migrated, the private portion of the key is never exposed outside the TPM.
Computers that incorporate a TPM can also create a key that has not only been wrapped, but is also tied to certain platform measurements. This type of key can be unwrapped only when those platform measurements have the same values that they had when the key was created. This process is referred to as “sealing the key to the TPM.” Decrypting the key is called unsealing. The TPM can also seal and unseal data that is generated outside the TPM. With this sealed key and software, such as BitLocker Drive Encryption, you can lock data until specific hardware or software conditions are met.
With a TPM, private portions of key pairs are kept separate from the memory that is controlled by the operating system. Keys can be sealed to the TPM, and certain assurances about the state of a system (assurances that define the trustworthiness of a system) can be made before the keys are unsealed and released for use. Because the TPM uses its own internal firmware and logic circuits to process instructions, it does not rely on the operating system, and it is not exposed to vulnerabilities that might exist in the operating system or application software.
For info about which versions of Windows support which versions of the TPM, see [Trusted Platform Module technology overview](trusted-platform-module-overview.md). The features that are available in the versions are defined in specifications by the Trusted Computing Group (TCG). For more info, see the Trusted Platform Module page on the Trusted Computing Group website: [Trusted Platform Module](http://www.trustedcomputinggroup.org/developers/trusted_platform_module).
The following sections provide an overview of the technologies that support the TPM:
- [Measured Boot with support for attestation](#measured-boot-with-support-for-attestation)
- [TPM-based Virtual Smart Card](#tpm-based-virtual-smart-card)
- [TPM-based certificate storage](#tpm-based-certificate-storage)
- [TPM Cmdlets](#tpm-cmdlets)
- [Physical presence interface](#physical-presence-interface)
- [TPM 1.2 states and initialization](#tpm-12-states-and-initialization)
- [Endorsement keys](#endorsement-keys)
- [TPM Key Attestation](#key-attestation)
- [Anti-hammering](#anti-hammering)
The following topic describes the TPM Services that can be controlled centrally by using Group Policy settings:
[TPM Group Policy Settings](trusted-platform-module-services-group-policy-settings.md).
## Measured Boot with support for attestation
The Measured Boot feature provides antimalware software with a trusted (resistant to spoofing and tampering) log of all boot components. Antimalware software can use the log to determine whether components that ran before it are trustworthy versus infected with malware. It can also send the Measured Boot logs to a remote server for evaluation. The remote server can initiate remediation actions by interacting with software on the client or through out-of-band mechanisms, as appropriate.
## TPM-based Virtual Smart Card
The Virtual Smart Card emulates the functionality of traditional smart cards, but Virtual Smart Cards use the TPM chip that is available on an organization’s computers, rather than requiring the use of a separate physical smart card and reader. This greatly reduces the management and deployment cost of smart cards in an enterprise. To the end user, the Virtual Smart Card is always available on the computer. If a user needs to use more than one computer, a
Virtual Smart Card must be issued to the user for each computer. A computer that is shared among multiple users can host multiple Virtual Smart Cards, one for each user.
## TPM-based certificate storage
The TPM can be used to protect certificates and RSA keys. The TPM key storage provider (KSP) provides easy, convenient use of the TPM as a way of strongly protecting private keys. The TPM KSP can be used to generate keys when an organization enrolls for certificates, and the KSP is managed by templates in the UI. The TPM can also be used to protect certificates that are imported from an outside source. TPM-based certificates can be used exactly as standard certificates with the added functionality that the certificate can never leave the TPM from which the keys were generated. The TPM can now be used for crypto-operations through Cryptography API: Next Generation (CNG). For more info, see [Cryptography API: Next Generation](http://msdn.microsoft.com/library/windows/desktop/aa376210.aspx).
## TPM Cmdlets
You can manage the TPM using Windows PowerShell. For details, see [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx).
## Physical presence interface
For TPM 1.2, the TCG specifications for TPMs require physical presence (typically, pressing a key) for turning the TPM on, turning it off, or clearing it. These actions typically cannot be automated with scripts or other automation tools unless the individual OEM supplies them.
## TPM 1.2 states and initialization
For TPM 1.2, there are multiple possible states. Windows 10 automatically initializes the TPM, which brings it to an enabled, activated, and owned state.
## Endorsement keys
For a TPM to be usable by a trusted application, it must contain an endorsement key, which is an RSA key pair. The private half of the key pair is held inside the TPM, and it is never revealed or accessible outside the TPM.
## Key attestation
TPM key attestation allows a certification authority to verify that a private key is actually protected by a TPM and that the TPM is one that the certification authority trusts. Endorsement keys which have been proven valid can be used to bind the user identity to a device. Moreover, the user certificate with a TPM attested key provides higher security assurance backed up by the non-exportability, anti-hammering, and isolation of keys provided by a TPM.
## Anti-hammering
When a TPM processes a command, it does so in a protected environment, for example, a dedicated microcontroller on a discrete chip or a special hardware-protected mode on the main CPU. A TPM can be used to create a cryptographic key that is not disclosed outside the TPM, but is able to be used in the TPM after the correct authorization value is provided.
TPMs have anti-hammering protection that is designed to prevent brute force attacks, or more complex dictionary attacks, that attempt to determine authorization values for using a key. The basic approach is for the TPM to allow only a limited number of authorization failures before it prevents more attempts to use keys and locks. Providing a failure count for individual keys is not technically practical, so TPMs have a global lockout when too many authorization failures occur.
Because many entities can use the TPM, a single authorization success cannot reset the TPM’s anti-hammering protection. This prevents an attacker from creating a key with a known authorization value and then using it to reset the TPM’s protection. Generally, TPMs are designed to forget about authorization failures after a period of time so the TPM does not enter a lockout state unnecessarily. A TPM owner password can be used to reset the TPM’s lockout logic.
### TPM 2.0 anti-hammering
TPM 2.0 has well defined anti-hammering behavior. This is in contrast to TPM 1.2 for which the anti-hammering protection was implemented by the manufacturer, and the logic varied widely throughout the industry.
For systems with TPM 2.0, the TPM is configured by Windows to lock after 32 authorization failures and to forget one authorization failure every two hours. This means that a user could quickly attempt to use a key with the wrong authorization value 32 times. For each of the 32 attempts, the TPM records if the authorization value was correct or not. This inadvertently causes the TPM to enter a locked state after 32 failed attempts.
Attempts to use a key with an authorization value for the next two hours would not return success or failure; instead the response indicates that the TPM is locked. After two hours, one authorization failure is forgotten and the number of authorization failures remembered by the TPM drops to 31, so the TPM leaves the locked state and returns to normal operation. With the correct authorization value, keys could be used normally if no authorization failures occur during the next two hours. If a period of 64 hours elapses with no authorization failures, the TPM does not remember any authorization failures, and 32 failed attempts could occur again.
Windows 8 Certification does not require TPM 2.0 systems to forget about authorization failures when the system is fully powered off or when the system has hibernated. Windows does require that authorization failures are forgotten when the system is running normally, in a sleep mode, or in low power states other than off. If a Windows system with TPM 2.0 is locked, the TPM leaves lockout mode if the system is left on for two hours.
The anti-hammering protection for TPM 2.0 can be fully reset immediately by sending a reset lockout command to the TPM and providing the TPM owner password. By default, Windows automatically provisions TPM 2.0 and stores the TPM owner password for use by system administrators.
In some enterprise situations, the TPM owner authorization value is configured to be stored centrally in Active Directory, and it is not stored on the local system. An administrator can launch the TPM MMC and choose to reset the TPM lockout time. If the TPM owner password is stored locally, it is used to reset the lockout time. If the TPM owner password is not available on the local system, the administrator needs to provide it. If an administrator attempts to reset the TPM lockout state with the wrong TPM owner password, the TPM does not allow another attempt to reset the lockout state for 24 hours.
TPM 2.0 allows some keys to be created without an authorization value associated with them. These keys can be used when the TPM is locked. For example, BitLocker with a default TPM-only configuration is able to use a key in the TPM to start Windows, even when the TPM is locked.
### Rationale behind the defaults
Originally, BitLocker allowed from 4 to 20 characters for a PIN.
Windows Hello has its own PIN for logon, which can be 4 to 127 characters.
Both BitLocker and Windows Hello use the TPM to prevent PIN brute-force attacks.
The TPM can be configured to use Dictionary Attack Prevention parameters ([lockout threshold and lockout duration](trusted-platform-module-services-group-policy-settings.md)) to control how many failed authorizations attempts are allowed before the TPM is locked out, and how much time must elapse before another attempt can be made.
The Dictionary Attack Prevention Parameters provide a way to balance security needs with usability.
For example, when BitLocker is used with a TPM + PIN configuration, the number of PIN guesses is limited over time.
A TPM 2.0 in this example could be configured to allow only 32 PIN guesses immediately, and then only one more guess every two hours.
This totals a maximum of about 4415 guesses per year.
If the PIN is 4 digits, all 9999 possible PIN combinations could be attempted in a little over two years.
Increasing the PIN length requires a greater number of guesses for an attacker.
In that case, the lockout duration between each guess can be shortened to allow legitimate users to retry a failed attempt sooner, while maintaining a similar level of protection.
Beginning with Windows 10, version 1703, the minimum length for the BitLocker PIN was increased to 6 characters to better align with other Windows features that leverage TPM 2.0, including Windows Hello.
To help organizations with the transition, beginning with Windows 10, version 1709 and Windows 10, version 1703 with the October 2017 [cumulative update](https://support.microsoft.com/help/4018124) installed, the BitLocker PIN length is 6 characters by default, but it can be reduced to 4 characters.
If the minimum PIN length is reduced from the default of six characters, then the TPM 2.0 lockout period will be extended.
### TPM-based smart cards
The Windows TPM-based smart card, which is a virtual smart card, can be configured to allow sign in to the system. In contrast with physical smart cards, the sign-in process uses a TPM-based key with an authorization value. The following list shows the advantages of virtual smart cards:
- Physical smart cards can enforce lockout for only the physical smart card PIN, and they can reset the lockout after the correct PIN is entered. With a virtual smart card, the TPM’s anti-hammering protection is not reset after a successful authentication. The allowed number of authorization failures before the TPM enters lockout includes many factors.
- Hardware manufacturers and software developers have the option to use the security features of the TPM to meet their requirements.
- The intent of selecting 32 failures as the lock-out threshold is so users rarely lock the TPM (even when learning to type new passwords or if they frequently lock and unlock their computers). If users lock the TPM, they must to wait two hours or use some other credential to sign in, such as a user name and password.
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)
- [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx)
- [TPM WMI providers](https://msdn.microsoft.com/library/aa376476.aspx)
- [Prepare your organization for BitLocker: Planning and Policies - TPM configurations](https://technet.microsoft.com/itpro/windows/keep-secure/prepare-your-organization-for-bitlocker-planning-and-policies#bkmk-tpmconfigurations)

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---
title: TPM recommendations (Windows 10)
description: This topic provides recommendations for Trusted Platform Module (TPM) technology for Windows 10.
ms.assetid: E85F11F5-4E6A-43E7-8205-672F77706561
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
ms.localizationpriority: high
author: brianlic-msft
ms.date: 10/27/2017
---
# TPM recommendations
**Applies to**
- Windows 10
- Windows Server 2016
This topic provides recommendations for Trusted Platform Module (TPM) technology for Windows 10.
For a basic feature description of TPM, see the [Trusted Platform Module Technology Overview](trusted-platform-module-overview.md).
## TPM design and implementation
Traditionally, 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, however, a TPM must be provisioned. Windows 10 automatically provisions a TPM, but if the user is planning to reinstall the operating system, he or she may need to clear the TPM before reinstalling so that Windows can take full advantage of the TPM.
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).
OEMs implement the TPM as a component in a trusted computing platform, such as a PC, tablet, or phone. Trusted computing platforms use the TPM to support privacy and security scenarios that software alone cannot achieve. For example, software alone cannot reliably report whether malware is present during the system startup process. The close integration between TPM and platform increases the transparency of the startup process and supports evaluating device health by enabling reliable measuring and reporting of the software that starts the device. Implementation of a TPM as part of a trusted computing platform provides a hardware root of trust—that is, it behaves in a trusted way. For example, if a key stored in a TPM has properties that disallow exporting the key, that key truly cannot leave the TPM.
The TCG designed the TPM as a low-cost, mass-market security solution that addresses the requirements of different customer segments. There are variations in the security properties of different TPM implementations just as there are variations in customer and regulatory requirements for different sectors. In public-sector procurement, for example, some governments have clearly defined security requirements for TPMs whereas others do not.
## TPM 1.2 vs. 2.0 comparison
From an industry standard, Microsoft has been an industry leader in moving and standardizing on TPM 2.0, which has many key realized benefits across algorithms, crypto, hierarchy, root keys, authorization and NV RAM.
## Why TPM 2.0?
TPM 2.0 products and systems have important security advantages over TPM 1.2, including:
- The TPM 1.2 spec only allows for the use of RSA and the SHA-1 hashing algorithm.
- For security reasons, some entities are moving away from SHA-1. Notably, NIST has required many federal agencies to move to SHA-256 as of 2014, and technology leaders, including Microsoft and Google have announced they will remove support for SHA-1 based signing or certificates in 2017.
- TPM 2.0 **enables greater crypto agility** by being more flexible with respect to cryptographic algorithms.
- TPM 2.0 supports newer algorithms, which can improve drive signing and key generation performance. For the full list of supported algorithms, see the [TCG Algorithm Registry](http://www.trustedcomputinggroup.org/tcg-algorithm-registry/). Some TPMs do not support all algorithms.
- For the list of algorithms that Windows supports in the platform cryptographic storage provider, see [CNG Cryptographic Algorithm Providers](https://msdn.microsoft.com/library/windows/desktop/bb931354(v=vs.85).aspx).
- TPM 2.0 achieved ISO standardization ([ISO/IEC 11889:2015](http://blogs.microsoft.com/cybertrust/2015/06/29/governments-recognize-the-importance-of-tpm-2-0-through-iso-adoption/)).
- Use of TPM 2.0 may help eliminate the need for OEMs to make exception to standard configurations for certain countries and regions.
- TPM 2.0 offers a more **consistent experience** across different implementations.
- TPM 1.2 implementations vary in policy settings. This may result in support issues as lockout policies vary.
- TPM 2.0 lockout policy is configured by Windows, ensuring a consistent dictionary attack protection guarantee.
- While TPM 1.2 parts are discrete silicon components which are typically soldered on the motherboard, TPM 2.0 is available as a **discrete (dTPM)** silicon component in a single semiconductor package, an **integrated** component incorporated in one or more semiconductor packages - alongside other logic units in the same package(s) - and as a **firmware (fTPM)** based component running in a trusted execution environment (TEE) on a general purpose SoC.
## Discrete, Integrated or Firmware TPM?
There are three implementation options for TPMs:
- Discrete TPM chip as a separate component in its own semiconductor package
- Integrated TPM solution, using dedicated hardware integrated into one or more semiconductor packages alongside, but logically separate from, other components
- Firmware TPM solution, running the TPM in firmware in a Trusted Execution mode of a general purpose computation unit
Windows uses any compatible TPM in the same way. Microsoft does not take a position on which way a TPM should be implemented and there is a wide ecosystem of available TPM solutions which should suit all needs.
## Is there any importance for TPM for consumers?
For end consumers, TPM is behind the scenes but is still very relevant. TPM is used for Windows Hello, Windows Hello for Business and in the future, will be a component of many other key security features in Windows. TPM secures the PIN, helps encrypt passwords, and builds on our overall Windows 10 experience story for security as a critical pillar. Using Windows on a system with a TPM enables a deeper and broader level of security coverage.
## TPM 2.0 Compliance for Windows 10
### Windows 10 for desktop editions (Home, Pro, Enterprise, and Education)
- Since July 28, 2016, all new device models, lines or series (or if you are updating the hardware configuration of a existing model, line or series with a major update, such as CPU, graphic cards) must implement and enable by default TPM 2.0 (details in section 3.7 of the [Minimum hardware requirements](https://msdn.microsoft.com/library/windows/hardware/dn91508.aspx) page). The requirement to enable TPM 2.0 only applies to the manufacturing of new devices. For TPM recommendations for specific Windows features, see [TPM and Windows Features](#tpm-and-windows-features).
### IoT Core
- TPM is optional on IoT Core.
### Windows Server 2016
- TPM is optional for Windows Server SKUs unless the SKU meets the additional qualification (AQ) criteria for the Host Guardian Services scenario in which case TPM 2.0 is required.
## TPM and Windows Features
The following table defines which Windows features require TPM support.
| Windows Features | TPM Required | Supports TPM 1.2 | Supports TPM 2.0 | Details |
|-------------------------|--------------|--------------------|--------------------|----------|
| Measured Boot | Yes | Yes | Yes | Measured Boot requires TPM 1.2 or 2.0 and UEFI Secure Boot |
| BitLocker | Yes | Yes | Yes | TPM 1.2 or 2.0 is required |
| Device Encryption | Yes | N/A | Yes | Device Encryption requires Modern Standby/Connected Standby certification, which requires TPM 2.0. |
| Device Guard | No | Yes | Yes | |
| Credential Guard | No | Yes | Yes | Windows 10, version 1507 (End of Life as of May 2017) only supported TPM 2.0 for Credential Guard. Beginning with Windows 10, version 1511, TPM 1.2 and 2.0 are supported. |
| Device Health Attestation| Yes | Yes | Yes | |
| Windows Hello/Windows Hello for Business| No | Yes | Yes | Azure AD join supports both versions of TPM, but requires TPM with keyed-hash message authentication code (HMAC) and Endorsement Key (EK) certificate for key attestation support. |
| UEFI Secure Boot | No | Yes | Yes | |
| TPM Platform Crypto Provider Key Storage Provider| Yes | Yes| Yes | |
| Virtual Smart Card | Yes | Yes | Yes | |
| Certificate storage | No | Yes | Yes | TPM is only required when the certificate is stored in the TPM. |
## OEM Status on TPM 2.0 system availability and certified parts
Government customers and enterprise customers in regulated industries may have acquisition standards that require use of common certified TPM parts. As a result, OEMs, who provide the devices, may be required to use only certified TPM components on their commercial class systems. For more information, contact your OEM or hardware vendor.
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)

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---
title: Trusted Platform Module Technology Overview (Windows 10)
description: This topic for the IT professional describes the Trusted Platform Module (TPM) and how Windows uses it for access control and authentication.
ms.assetid: face8932-b034-4319-86ac-db1163d46538
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
ms.localizationpriority: high
author: brianlic-msft
ms.date: 07/27/2017
---
# Trusted Platform Module Technology Overview
**Applies to**
- Windows 10
- Windows Server 2016
This topic for the IT professional describes the Trusted Platform Module (TPM) and how Windows uses it for access control and authentication.
## Feature description
Trusted Platform Module (TPM) technology is designed to provide hardware-based, security-related functions. A TPM chip is a secure crypto-processor that is designed to carry out cryptographic operations. The chip includes multiple physical security mechanisms to make it tamper resistant, and malicious software is unable to tamper with the security functions of the TPM. Some of the key advantages of using TPM technology are that you can:
- Generate, store, and limit the use of cryptographic keys.
- Use TPM technology for platform device authentication by using the TPM’s unique RSA key, which is burned into itself.
- Help ensure platform integrity by taking and storing security measurements.
The most common TPM functions are used for system integrity measurements and for key creation and use. During the boot process of a system, the boot code that is loaded (including firmware and the operating system components) can be measured and recorded in the TPM. The integrity measurements can be used as evidence for how a system started and to make sure that a TPM-based key was used only when the correct software was used to boot the system.
TPM-based keys can be configured in a variety of ways. One option is to make a TPM-based key unavailable outside the TPM. This is good to mitigate phishing attacks because it prevents the key from being copied and used without the TPM. TPM-based keys can also be configured to require an authorization value to use them. If too many incorrect authorization guesses occur, the TPM will activate its dictionary attack logic and prevent further authorization value guesses.
Different versions of the TPM are defined in specifications by the Trusted Computing Group (TCG). For more information, consult the [TCG Web site](http://www.trustedcomputinggroup.org/work-groups/trusted-platform-module/).
### Automatic initialization of the TPM with Windows 10
Starting with Windows 10, the operating system automatically initializes and takes ownership of the TPM. This means that in most cases, we recommend that you avoid configuring the TPM through the TPM management console, **TPM.msc**. There are a few exceptions, mostly related to resetting or performing a clean installation on a PC. For more information, see [Clear all the keys from the TPM](initialize-and-configure-ownership-of-the-tpm.md#clear-all-the-keys-from-the-tpm).
In certain specific enterprise scenarios limited to Windows 10, versions 1507 and 1511, Group Policy might be used to back up the TPM owner authorization value in Active Directory. Because the TPM state persists across operating system installations, this TPM information is stored in a location in Active Directory that is separate from computer objects.
## Practical applications
Certificates can be installed or created on computers that are using the TPM. After a computer is provisioned, the RSA private key for a certificate is bound to the TPM and cannot be exported. The TPM can also be used as a replacement for smart cards, which reduces the costs associated with creating and disbursing smart cards.
Automated provisioning in the TPM reduces the cost of TPM deployment in an enterprise. New APIs for TPM management can determine if TPM provisioning actions require physical presence of a service technician to approve TPM state change requests during the boot process.
Antimalware software can use the boot measurements of the operating system start state to prove the integrity of a computer running Windows 10 or Windows Server 2016. These measurements include the launch of Hyper-V to test that datacenters using virtualization are not running untrusted hypervisors. With BitLocker Network Unlock, IT administrators can push an update without concerns that a computer is waiting for PIN entry.
The TPM has several Group Policy settings that might be useful in certain enterprise scenarios. For more info, see [TPM Group Policy Settings](trusted-platform-module-services-group-policy-settings.md).
## New and changed functionality
For more info on new and changed functionality for Trusted Platform Module in Windows 10, see [What's new in Trusted Platform Module?](https://technet.microsoft.com/itpro/windows/whats-new/whats-new-windows-10-version-1507-and-1511#trusted-platform-module).
## Device health attestation
Device health attestation enables enterprises to establish trust based on hardware and software components of a managed device. With device heath attestation, you can configure an MDM server to query a health attestation service that will allow or deny a managed device access to a secure resource.
Some things that you can check on the device are:
- Is Data Execution Prevention supported and enabled?
- Is BitLocker Drive Encryption supported and enabled?
- Is SecureBoot supported and enabled?
> [!NOTE]
> The device must be running Windows 10 and it must support at least TPM 2.0.
## Supported versions
| TPM version | Windows 10 | Windows Server 2016 |
|-------------|------------|---------------------|
| TPM 1.2 | X | X |
| TPM 2.0 | X | X |
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)
- [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx)
- [Prepare your organization for BitLocker: Planning and Policies - TPM configurations](https://technet.microsoft.com/itpro/windows/keep-secure/prepare-your-organization-for-bitlocker-planning-and-policies#bkmk-tpmconfigurations)

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---
title: TPM Group Policy settings (Windows 10)
description: This topic describes the Trusted Platform Module (TPM) Services that can be controlled centrally by using Group Policy settings.
ms.assetid: 54ff1c1e-a210-4074-a44e-58fee26e4dbd
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
author: brianlic-msft
ms.date: 08/16/2017
---
# TPM Group Policy settings
**Applies to**
- Windows 10
- Windows Server 2016
This topic describes the Trusted Platform Module (TPM) Services that can be controlled centrally by using Group Policy settings.
The Group Policy settings for TPM services are located at:
**Computer Configuration\\Administrative Templates\\System\\Trusted Platform Module Services\\**
The following Group Policy settings were introduced in Window 10:
## Configure the list of blocked TPM commands
This policy setting allows you to manage the Group Policy list of Trusted Platform Module (TPM) commands that are blocked by Windows.
If you enable this policy setting, Windows will block the specified commands from being sent to the TPM on the computer. TPM commands are referenced by a command number. For example, command number 129 is **TPM\_OwnerReadInternalPub**, and command number 170 is **TPM\_FieldUpgrade**. To find the command number that is associated with each TPM command, at the command prompt, type **tpm.msc** to open the TPM Management Console and navigate to the **Command Management** section.
If you disable or do not configure this policy setting, only those TPM commands that are specified through the default or local lists can be blocked by Windows. The default list of blocked TPM commands is preconfigured by Windows.
- You can view the default list by typing **tpm.msc** at the command prompt, navigating to the **Command Management** section, and exposing the **On Default Block List** column.
- The local list of blocked TPM commands is configured outside of Group Policy by running the TPM Management Console or scripting using the **Win32\_Tpm** interface.
For information how to enforce or ignore the default and local lists of blocked TPM commands, see
- [Ignore the default list of blocked TPM commands](#ignore-the-default-list-of-blocked-tpm-commands)
- [Ignore the local list of blocked TPM commands](#ignore-the-local-list-of-blocked-tpm-commands)
## Ignore the default list of blocked TPM commands
This policy setting allows you to enforce or ignore the computer's default list of blocked Trusted Platform Module (TPM) commands.
The default list of blocked TPM commands is preconfigured by Windows. You can view the default list by typing **tpm.msc** at the command prompt to open the TPM Management Console, navigating to the **Command Management** section, and exposing the **On Default Block List** column. Also see the related policy setting, [Configure the list of blocked TPM commands](#configure-the-list-of-blocked-tpm-commands).
If you enable this policy setting, the Windows operating system will ignore the computer's default list of blocked TPM commands, and it will block only those TPM commands that are specified by Group Policy or the local list.
If you disable or do not configure this policy setting, Windows will block the TPM commands in the default list, in addition to the commands that are specified by Group Policy and the local list of blocked TPM commands.
## Ignore the local list of blocked TPM commands
This policy setting allows you to enforce or ignore the computer's local list of blocked Trusted Platform Module (TPM) commands.
The local list of blocked TPM commands is configured outside of Group Policy by typing **tpm.msc** at the command prompt to open the TPM Management Console, or scripting using the **Win32\_Tpm** interface. (The default list of blocked TPM commands is preconfigured by Windows.) Also see the related policy setting, [Configure the list of blocked TPM commands](#configure-the-list-of-blocked-tpm-commands).
If you enable this policy setting, the Windows operating system will ignore the computer's local list of blocked TPM commands, and it will block only those TPM commands that are specified by Group Policy or the default list.
If you disable or do not configure this policy setting, Windows will block the TPM commands in the local list, in addition to the commands that are specified in Group Policy and the default list of blocked TPM commands.
## Configure the level of TPM owner authorization information available to the operating system
This policy setting configures how much of the TPM owner authorization information is stored in the registry of the local computer. Depending on the amount of TPM owner authorization information that is stored locally, the Windows operating system and TPM-based applications can perform certain actions in the TPM that require TPM owner authorization without requiring the user to enter the TPM owner password.
> [!IMPORTANT]
> This policy setting is not available in the Windows 10, version 1607 and Windows Server 2016 and later versions of the ADMX files.
There are three TPM owner authentication settings that are managed by the Windows operating system. You can choose a value of **Full**, **Delegate**, or **None**.
- **Full**   This setting stores the full TPM owner authorization, the TPM administrative delegation blob, and the TPM user delegation blob in the local registry. With this setting, you can use the TPM without requiring remote or external storage of the TPM owner authorization value. This setting is appropriate for scenarios that do not require you to reset the TPM anti-hammering logic or change the TPM owner authorization value. Some TPM-based applications may require that this setting is changed before features that depend on the TPM anti-hammering logic can be used.
- **Delegated**   This setting stores only the TPM administrative delegation blob and the TPM user delegation blob in the local registry. This setting is appropriate for use with TPM-based applications that depend on the TPM antihammering logic. This is the default setting in Windows.
- **None**   This setting provides compatibility with previous operating systems and applications. You can also use it for scenarios when TPM owner authorization cannot be stored locally. Using this setting might cause issues with some TPM-based applications.
> [!NOTE]
> If the operating system managed TPM authentication setting is changed from **Full** to **Delegated**, the full TPM owner authorization value will be regenerated, and any copies of the previously set TPM owner authorization value will be invalid.
**Registry information**
Registry key: HKEY\_LOCAL\_MACHINE\\SOFTWARE\\Policies\\Microsoft\\TPM
DWORD: OSManagedAuthLevel
The following table shows the TPM owner authorization values in the registry.
| Value Data | Setting |
|------------|-----------|
| 0 | None |
| 2 | Delegated |
| 4 | Full |
 
If you enable this policy setting, the Windows operating system will store the TPM owner authorization in the registry of the local computer according to the TPM authentication setting you choose.
If you disable or do not configure this policy setting, and the **Turn on TPM backup to Active Directory Domain Services** policy setting is also disabled or not configured, the default setting is to store the full TPM authorization value in the local registry. If this policy is disabled or not
configured, and the **Turn on TPM backup to Active Directory Domain Services** policy setting is enabled, only the administrative delegation and the user delegation blobs are stored in the local registry.
## Standard User Lockout Duration
This policy setting allows you to manage the duration in minutes for counting standard user authorization failures for Trusted Platform Module (TPM) commands requiring authorization. An authorization failure occurs each time a standard user sends a command to the TPM and receives an error response that indicates an authorization failure occurred. Authorization failures that are older than the duration you set are ignored. If the number of TPM commands with an authorization failure within the lockout duration equals a threshold, a standard user is prevented from sending commands that require
authorization to the TPM.
The TPM is designed to protect itself against password guessing attacks by entering a hardware lockout mode when it receives too many commands with an incorrect authorization value. When the TPM enters a lockout mode, it is global for all users (including administrators) and for Windows features such as BitLocker Drive Encryption.
This setting helps administrators prevent the TPM hardware from entering a lockout mode by slowing the speed at which standard users can send commands that require authorization to the TPM.
For each standard user, two thresholds apply. Exceeding either threshold prevents the user from sending a command that requires authorization to the TPM. Use the following policy settings to set the lockout duration:
- [Standard User Individual Lockout Threshold](#standard-user-individual-lockout-threshold)   This value is the maximum number of authorization failures that each standard user can have before the user is not allowed to send commands that require authorization to the TPM.
- [Standard User Total Lockout Threshold](#standard-user-total-lockout-threshold)   This value is the maximum total number of authorization failures that all standard users can have before all standard users are not allowed to send commands that require authorization to the TPM.
An administrator with the TPM owner password can fully reset the TPM's hardware lockout logic by using the TPM Management Console (tpm.msc). Each time an administrator resets the TPM's hardware lockout logic, all prior standard user TPM authorization failures are ignored. This allows standard users to immediately use the TPM normally.
If you do not configure this policy setting, a default value of 480 minutes (8 hours) is used.
## Standard User Individual Lockout Threshold
This policy setting allows you to manage the maximum number of authorization failures for each standard user for the Trusted Platform Module (TPM). This value is the maximum number of authorization failures that each standard user can have before the user is not allowed to send commands that require authorization to the TPM. If the number of authorization failures for the user within the duration that is set for the **Standard User Lockout Duration** policy setting equals this value, the standard user is prevented from sending commands that require authorization to the Trusted Platform Module (TPM).
This setting helps administrators prevent the TPM hardware from entering a lockout mode by slowing the speed at which standard users can send commands that require authorization to the TPM.
An authorization failure occurs each time a standard user sends a command to the TPM and receives an error response indicating an authorization failure occurred. Authorization failures older than the duration are ignored.
An administrator with the TPM owner password can fully reset the TPM's hardware lockout logic by using the TPM Management Console (tpm.msc). Each time an administrator resets the TPM's hardware lockout logic, all prior standard user TPM authorization failures are ignored. This allows standard users to immediately use the TPM normally.
If you do not configure this policy setting, a default value of 4 is used. A value of zero means that the operating system will not allow standard users to send commands to the TPM, which might cause an authorization failure.
## Standard User Total Lockout Threshold
This policy setting allows you to manage the maximum number of authorization failures for all standard users for the Trusted Platform Module (TPM). If the total number of authorization failures for all standard users within the duration that is set for the **Standard User Lockout Duration** policy equals this value, all standard users are prevented from sending commands that require authorization to the Trusted Platform Module (TPM).
This setting helps administrators prevent the TPM hardware from entering a lockout mode because it slows the speed standard users can send commands requiring authorization to the TPM.
An authorization failure occurs each time a standard user sends a command to the TPM and receives an error response indicating an authorization failure occurred. Authorization failures older than the duration are ignored.
An administrator with the TPM owner password can fully reset the TPM's hardware lockout logic by using the TPM Management Console (tpm.msc). Each time an administrator resets the TPM's hardware lockout logic, all prior standard user TPM authorization failures are ignored. This allows standard users to immediately use the TPM normally.
If you do not configure this policy setting, a default value of 9 is used. A value of zero means that the operating system will not allow standard users to send commands to the TPM, which might cause an authorization failure.
> [!IMPORTANT]
> The **Turn on TPM backup to Active Directory Domain Services** is not available in the Windows 10, version 1607 and Windows Server 2016 and later versions of the ADMX files.
If you enable this policy setting, TPM owner information will be automatically and silently backed up to AD DS when you use Windows to set or change a TPM owner password. When this policy setting is enabled, a TPM owner password cannot be set or changed unless the computer is connected to the domain and the AD DS backup succeeds.
If you disable or do not configure this policy setting, TPM owner information will not be backed up to AD DS.
## Configure the system to use legacy Dictionary Attack Prevention Parameters setting for TPM 2.0
Introduced in Windows 10, version 1703, this policy setting configures the TPM to use the Dictionary Attack Prevention Parameters (lockout threshold and recovery time) to the values that were used for Windows 10 Version 1607 and below.
> [!IMPORTANT]
> Setting this policy will take effect only if:
- The TPM was originally prepared using a version of Windows after Windows 10 Version 1607
- The system has a TPM 2.0.
> [!NOTE]
> Enabling this policy will only take effect after the TPM maintenance task runs (which typically happens after a system restart). Once this policy has been enabled on a system and has taken effect (after a system restart), disabling it will have no impact and the system's TPM will remain configured using the legacy Dictionary Attack Prevention parameters, regardless of the value of this group policy. The only ways for the disabled setting of this policy to take effect on a system where it was once enabled are to either:
> - Disable it from group policy
> - Clear the TPM on the system
## Related topics
- [Trusted Platform Module](trusted-platform-module-top-node.md) (list of topics)
- [TPM Cmdlets in Windows PowerShell](http://technet.microsoft.com/library/jj603116.aspx)
- [Prepare your organization for BitLocker: Planning and Policies - TPM configurations](https://technet.microsoft.com/itpro/windows/keep-secure/prepare-your-organization-for-bitlocker-planning-and-policies#bkmk-tpmconfigurations)

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---
title: Trusted Platform Module (Windows 10)
description: This topic for the IT professional provides links to information about the Trusted Platform Module (TPM) and how Windows uses it for access control and authentication.
ms.prod: w10
ms.mktglfcycl: deploy
ms.sitesec: library
ms.pagetype: security
ms.localizationpriority: high
author: brianlic-msft
ms.date: 07/27/2017
---
# Trusted Platform Module
**Applies to**
- Windows 10
- Windows Server 2016
Trusted Platform Module (TPM) technology is designed to provide hardware-based, security-related functions. A TPM chip is a secure crypto-processor that helps you with actions such as generating, storing, and limiting the use of cryptographic keys. The following topics provide details.
<!-- The description for "Manage TPM lockout" might need updating-- the topic is being revised in December 2016 or January 2017. -->
| Topic | Description |
|-------|-------------|
| [Trusted Platform Module Overview](trusted-platform-module-overview.md) | Provides an overview of the Trusted Platform Module (TPM) and how Windows uses it for access control and authentication. |
| [TPM fundamentals](tpm-fundamentals.md) | Provides background about how a TPM can work with cryptographic keys. Also describes technologies that work with the TPM, such as TPM-based virtual smart cards. |
| [TPM Group Policy settings](trusted-platform-module-services-group-policy-settings.md) | Describes TPM services that can be controlled centrally by using Group Policy settings. |
| [Back up the TPM recovery information to AD DS](backup-tpm-recovery-information-to-ad-ds.md) | For Windows 10, version 1511 and Windows 10, version 1507 only, describes how to back up a computer’s TPM information to Active Directory Domain Services. |
| [Manage TPM commands](manage-tpm-commands.md) | Describes methods by which a local or domain administrator can block or allow specific TPM commands. |
| [Manage TPM lockout](manage-tpm-lockout.md) | Describes how TPM lockout works (to help prevent tampering or malicious attacks), and outlines ways to work with TPM lockout settings. |
| [Change the TPM owner password](change-the-tpm-owner-password.md) | In most cases, applies to Windows 10, version 1511 and Windows 10, version 1507 only. Tells how to change the TPM owner password. |
| [View status, clear, or troubleshoot the TPM](initialize-and-configure-ownership-of-the-tpm.md) | Describes actions you can take through the TPM snap-in, TPM.msc: view TPM status, troubleshoot TPM initialization, and clear keys from the TPM. Also, for TPM 1.2 and Windows 10, version 1507 or 1511, describes how to turn the TPM on or off. |
| [Understanding PCR banks on TPM 2.0 devices](switch-pcr-banks-on-tpm-2-0-devices.md) | Provides background about what happens when you switch PCR banks on TPM 2.0 devices. |
| [TPM recommendations](tpm-recommendations.md) | Discusses aspects of TPMs such as the difference between TPM 1.2 and 2.0, and the Windows 10 features for which a TPM is required or recommended. |