Trusted Platform Module (TPM) | TPM Information for Windows 11

Trusted Platform Module (TPM) | TPM Information for Windows 11

Trusted Platform Module (TPM, also known as ISO/IEC 11889) is an international standard for a secure cryptoprocessor, a dedicated microcontroller designed to secure hardware through integrated cryptographic keys.

Trusted Platform Module (TPM) was conceived by a computer industry consortium called Trusted Computing Group (TCG), and was standardized by International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) in 2009 as ISO/IEC 11889.

TCG continued to revise the TPM specifications. The last revised edition of TPM Main Specification Version 1.2 was published on March 3, 2011. It consisted of three parts, based on their purpose. For the second major version of TPM, however, TCG released TPM Library Specification 2.0. Its latest edition and errata were published in 2019.

Overview

Trusted Platform Module provides

• A hardware random number generator
• Facilities for the secure generation of cryptographic keys for limited uses.
• Remote attestation: Creates a nearly unforgeable hash key summary of the hardware and software configuration. The software in charge of hashing the configuration data determines the extent of the summary. This allows a third party to verify that the software has not been changed.
• Binding: Encrypts data using the TPM bind key, a unique RSA key descended from a storage key^{[clarification needed]}.
• Sealing: Similar to binding, but in addition, specifies the TPM state for the data to be decrypted (unsealed).
• Other Trusted Computing functions for the data to be decrypted (unsealed).

Computer programs can use a TPM to authenticate hardware devices, since each TPM chip has a unique and secret Endorsement Key (EK) burned in as it is produced. Pushing the security down to the hardware level provides more protection than a software-only solution

 

Uses

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The United States Department of Defense (DoD) specifies that "new computer assets (e.g., server, desktop, laptop, thin client, tablet, smartphone, personal digital assistant, mobile phone) procured to support DoD will include a TPM version 1.2 or higher where required by DISA STIGs and where such technology is available." DoD anticipates that TPM is to be used for device identification, authentication, encryption, and device integrity verification.

Platform integrity

The primary scope of TPM is to assure the integrity of a platform. In this context, "integrity" means "behave as intended", and a "platform" is any computer device regardless of its operating system. It is to ensure that the boot process starts from a trusted combination of hardware and software, and continues until the operating system has fully booted and applications are running.

The responsibility of assuring said integrity using TPM is with the firmware and the operating system. For example, Unified Extensible Firmware Interface (UEFI) can use TPM to form a root of trust: The TPM contains several Platform Configuration Registers (PCRs) that allow secure storage and reporting of security-relevant metrics. These metrics can be used to detect changes to previous configurations and decide how to proceed. Good examples can be found in Linux Unified Key Setup (LUKS), BitLocker and PrivateCore vCage memory encryption. (See below.)

Another example of platform integrity via TPM is in the use of Microsoft Office 365 licensing and Outlook Exchange.

An example of TPM use for platform integrity is the Trusted Execution Technology (TXT), which creates a chain of trust. It could remotely attest that a computer is using the specified hardware and software.

Disk encryption

Full disk encryption utilities, such as dm-crypt and BitLocker, can use this technology to protect the keys used to encrypt the computer's storage devices and provide integrity authentication for a trusted boot pathway that includes firmware and boot sector.

Password protection

Operating systems often require authentication (involving a password or other means) to protect keys, data or systems. If the authentication mechanism is implemented in software only, the access is prone to dictionary attacks. Since TPM is implemented in a dedicated hardware module, a dictionary attack prevention mechanism was built in, which effectively protects against guessing or automated dictionary attacks, while still allowing the user a sufficient and reasonable number of tries. Without this level of protection, only passwords with high complexity would provide sufficient protection.

Other uses and concerns

Any application can use a TPM chip for:

• Digital rights management (DRM)
• Windows Defender
• Windows Domain logon
• Protection and enforcement of software licenses
• Prevention of cheating in online games

Other uses exist, some of which give rise to privacy concerns. The "physical presence" feature of TPM addresses some of these concerns by requiring BIOS-level confirmation for operations such as activating, deactivating, clearing or changing ownership of TPM by someone who is physically present at the console of the machine.

There are five different types of TPM 2.0 implementations (listed in order from most to least secure):

·         Discrete TPMs are dedicated chips that implement TPM functionality in their own tamper resistant semiconductor package. They are theoretically the most secure type of TPM because the routines implemented in hardware should be more resistant to bugs^{[clarification needed]} versus routines implemented in software, and their packages are required to implement some tamper resistance.

·         Integrated TPMs are part of another chip. While they use hardware that resists software bugs, they are not required to implement tamper resistance. Intel has integrated TPMs in some of its chipsets.

·         Firmware TPMs are firmware-based (e.g. UEFI) solutions that run in a CPU's trusted execution environment. Intel, AMD and Qualcomm have implemented firmware TPMs.

·         Hypervisor TPMs are virtual TPMs provided by and rely on hypervisors, in an isolated execution environment that is hidden from the software running inside virtual machines to secure their code from the software in the virtual machines. They can provide a security level comparable to a firmware TPM.

·         Software TPMs are software emulators of TPMs that run with no more protection than a regular program gets within an operating system. They depend entirely on the environment that they run in, so they provide no more security than what can be provided by the normal execution environment, and they are vulnerable to their own software bugs and attacks that are penetrating the normal execution environment.^{[citation needed]} They are useful for development purposes.

 

 

The official TCG reference implementation of the TPM 2.0 Specification has been developed by Microsoft. It is licensed under BSD License and the source code is available on GitHub. Microsoft provides a Visual Studio solution and Linux autotools build scripts.

In 2018, Intel open-sourced its Trusted Platform Module 2.0 (TPM2) software stack with support for Linux and Microsoft Windows. The source code is hosted on GitHub and licensed under BSD License.

Infineon funded the development of an open source TPM middleware that complies with the Software Stack (TSS) Enhanced System API (ESAPI) specification of the TCG. It was developed by Fraunhofer Institute for Secure Information Technology (SIT).

IBM's Software TPM 2.0 is an implementation of the TCG TPM 2.0 specification. It is based on the TPM specification Parts 3 and 4 and source code donated by Microsoft. It contains additional files to complete the implementation. The source code is hosted on SourceForge and GitHub and licensed under BSD License.

TPM 1.2 vs TPM 2.0

While TPM 2.0 addresses many of the same use cases and has similar features, the details are different. TPM 2.0 is not backward compatible to TPM 1.2.

Specification	TPM 1.2	TPM 2.0
Architecture	The one-size-fits-all specification consists of three parts.	A complete specification consists of a platform-specific specification which references a common four-part TPM 2.0 library. Platform-specific specifications define what parts of the library are mandatory, optional, or banned for that platform; and detail other requirements for that platform. Platform-specific specifications include PC Client, mobile,and Automotive-Thin.
Algorithms	SHA-1 and RSA are required. AES is optional. Triple DES was once an optional algorithm in earlier versions of TPM 1.2, but has been banned in TPM 1.2 version 94. The MGF1 hash-based mask generation function that is defined in PKCS#1 is required.	The PC Client Platform TPM Profile (PTP) Specification requires SHA-1 and SHA-256 for hashes; RSA, ECC using the Barreto-Naehrig 256-bit curve and the NIST P-256 curve for public-key cryptography and asymmetric digital signature generation and verification; HMAC for symmetric digital signature generation and verification; 128-bit AES for symmetric-key algorithm; and the MGF1 hash-based mask generation function that is defined in PKCS#1 are required by the TCG PC Client Platform TPM Profile (PTP) Specification. Many other algorithms are also defined but are optional. Note that Triple DES was readded into TPM 2.0, but with restrictions some values in any 64-bit block.
Crypto Primitives	A random number generator, a public-key cryptographic algorithm, a cryptographic hash function, a mask generation function, digital signature generation and verification, and Direct Anonymous Attestation are required. Symmetric-key algorithms and exclusive or are optional. Key generation is also required.	A random number generator, public-key cryptographic algorithms, cryptographic hash functions, symmetric-key algorithms, digital signature generation and verification, mask generation functions, exclusive or, and ECC-based Direct Anonymous Attestation using the Barreto-Naehrig 256-bit curve are required by the TCG PC Client Platform TPM Profile (PTP) Specification. The TPM 2.0 common library specification also requires key generation and key derivation functions.
Hierarchy	One (storage)	Three (platform, storage and endorsement)
Root Keys	One (SRK RSA-2048)	Multiple keys and algorithms per hierarchy
Authorization	HMAC, PCR, locality, physical presence	Password, HMAC, and policy (which covers HMAC, PCR, locality, and physical presence).
NVRAM	Unstructured data	Unstructured data, Counter, Bitmap, Extend, PIN pass and fail

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