Trusted Platform Module
Trusted Platform Module (TPM) is an international standard for a secure cryptoprocessor, which is a dedicated microprocessor designed to secure hardware by integrating cryptographic keys into devices. TPM's technical specification was written by a computer industry consortium called Trusted Computing Group (TCG). International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) standardized the specification as ISO/IEC 11889 in 2009.
TCG continues to revise the TPM specification. It published revision 116 of the TPM specification version 1.2 on March 3, 2011, while draft revision 1.07 of the TPM specification version 2.0 was published for public review on March 13, 2014.
Trusted Platform Module offers facilities for the secure generation of cryptographic keys, and limitation of their use, in addition to a random number generator. It also includes capabilities such as remote attestation and sealed storage, as follows:
- Remote attestation – creates a nearly unforgeable hash key summary of the hardware and software configuration. The program hashing the configuration data determines the extent of the summary of the software. This allows a third party to verify that the software has not been changed.
- Binding – encrypts data using TPM bind key, a unique RSA key descended from a storage key.
- Sealing – encrypts data in a similar manner to binding, but in addition specifies a state in which TPM must be in order for the data to be decrypted (unsealed).
Software can use a Trusted Platform Module to authenticate hardware devices. Since each TPM chip has a unique and secret RSA key burned in as it is produced, it is capable of performing platform authentication.
Generally, pushing the security down to the hardware level in conjunction with software provides more protection than a software-only solution. However even where a TPM is used, a key would still be vulnerable while a software application that has obtained it from TPM is using it to perform encryption/decryption operations, as has been illustrated in the case of a cold boot attack. This problem is eliminated if key(s) used in TPM are not accessible on a bus or to external programs and all encryption/decryption is done in TPM.
An example of use is Intel's Trusted Execution Technology (TXT). Intel's TXT is used to create a "chain of trust", and to remotely attest that a computer has a specified hardware setup and is using specified software.
The United States Department of Defense 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." The TPM is to be used for device identification, authentication, encryption, measurement, and device integrity.
The primary scope of a TPM (in combination with other TCG implementations) is to assure the integrity of a platform. In this context "integrity" means "behave as intended", and a "platform" is generically any computer platform – not limited to PCs or a particular operating system: start the power-on boot process from a trusted condition and extend this trust until the operating system has fully booted and applications are running.
Together with the BIOS, TPM forms a "root of trust": TPM contains several PCRs (Platform Configuration Registers) that allow a secure storage and reporting of security relevant metrics. These metrics can be used to detect changes to previous configurations and derive decisions how to proceed. Good examples can be found in Linux Unified Key Setup (LUKS), and in Microsoft's BitLocker Drive Encryption and PrivateCore vCage memory encryption (see below).
Therefore the BIOS and the operating system have the primary responsibility to utilize TPM in order to assure platform integrity. Only then can applications and users running on that platform rely on its security characteristics, such as secure I/O "what you see is what you get", uncompromised keyboard entries, memory and storage operations.
Full disk encryption applications, such as SecureDoc, dm-crypt in modern Linux kernels, and BitLocker Drive Encryption in some versions of Windows, can use this technology to protect the keys used to encrypt the computer's hard disks and provide integrity authentication for a trusted boot pathway (for example BIOS, boot sector, etc.) A number of third party full disk encryption products also support TPM. TrueCrypt however decided not to use it.
Access to keys, data or systems is often protected and requires authentication by presenting a password. If the authentication mechanism is implemented in software only, the access typically 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. With this hardware based dictionary attack prevention, the user can opt for shorter or weaker passwords which are more memorable. Without this level of protection, only passwords with high complexity would provide sufficient protection.
Other uses and concerns
Almost any encryption-enabled application can, in theory, make use of a TPM, including:
- digital rights management
- 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.
Starting in 2006, many new laptop computers have been sold with a Trusted Platform Module chip built-in. In the future, this concept could be co-located on an existing motherboard chip in computers, or any other device where a TPM's facilities could be employed, such as a cell phone. On a PC, either the LPC bus or the SPI bus is used to connect to the TPM.
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.
|TPM 1.2||TPM 2.0|
|Algorithms||SHA-1, RSA||Agile. E.g., SHA-1, SHA-256, RSA, Elliptic curve cryptography P256|
|Crypto Primitives||RNG, SHA-1||RNG, RSA, HMAC, SHA-1, SHA-256|
|Hierarchy||One (storage)||Three (platform, storage, endorsement)|
|Root Keys||One (SRK RSA-2048)||Multiple keys and algorithms per hierarchy|
|Authorization||HMAC, PCR, locality, physical presence||Password, HMAC, policy|
|NV RAM||Unstructured data||Unstructured data, Counter, Bitmap, Extend|
The TPM 2.0 policy authorization includes the 1.2 HMAC, locality, physical presence, and PCR. It adds authorization based on an asymmetric digital signature, indirection to another authorization secret, counters and time limits, NVRAM values, a particular command or command parameters, and physical presence. It permits the ANDing and ORing of these authorization primitives to construct complex authorization policies.
TCG has faced resistance in some areas to deploy this technology, especially in academia, where some authors see possible uses not specifically related to Trusted Computing, which may raise privacy concerns. The concerns include the abuse of remote validation of software (where the manufacturer—and not the user who owns the computer system—decides what software is allowed to run) and possible ways to follow actions taken by the user being recorded in a database, in a manner that is completely undetectable to the user.
Currently TPM is used by nearly all PC and notebook manufacturers, primarily offered on professional product lines.
TPM is implemented by several vendors:
- Acer, Wipro, Asus, Dell, Inc., Gigabyte Technology, IBM, LG, Fujitsu, HP, Lenovo, MSI, Panasonic, Samsung, Supermicro, Sony, Eurocom Corporation, and Toshiba provide TPM integration on their devices.
- Infineon provides both TPM chips and TPM software, which is delivered as OEM versions with new computers, as well as separately by Infineon for products with TPM technology which complies to TCG standards.
- Wave Systems offers a broad range of client and server software, which runs on all TPM chip-sets. For instance, this software is pre-installed on several models from Dell and Gateway.
- Microsoft operating systems, Windows Vista and later use the chip in conjunction with the included disk encryption component named BitLocker. Microsoft has announced that from January 1, 2015 all computers will have to be equipped with a TPM 2.0 module in order to pass Windows 8.1 hardware certification.
- In 2006, with the introduction of first Macintosh models with Intel processors, Apple started to ship Macs with TPM. Apple never provided an official driver, but there was a port under GPL available. Apple has not shipped a computer with TPM since 2006.
- In 2011, Taiwanese manufacturer MSI launched its Windpad 110W tablet featuring an AMD CPU and Infineon Security Platform TPM, which ships with controlling software version 3.7. The chip is disabled by default but can be enabled with the included, pre-installed software.
- Oracle ships TPMs in their recent X- and T-Series Systems such as T3 or T4 series of servers. Support is included in Solaris 11.
- Google includes TPMs in Chromebooks as part of their security model.
- VMware's ESXi hypervisor has supported TPM since 4.x, and from 5.0 it is enabled by default.
- PrivateCore vCage uses TPM chips in conjunction with Intel Trusted Execution Technology (Intel TXT) to validate systems on bootup.
- Hardware Security Module
- Hengzhi chip
- Next-Generation Secure Computing Base
- Trusted Computing
- Unified Extensible Firmware Interface (UEFI)
- "ISO/IEC 11889-1:2009". ISO.org. International Organization for Standardization. Retrieved 29 November 2013.
- "Trusted Platform Module (TPM) Specifications". Trusted Computing Group.
- "Trusted Platform Module Library". Trusted Computing Group.
- "Benchmarking the True Random Number Generator of TPM Chips". Retrieved 2012-06-04.
- "TPM Main Specification Level 2 Version 1.2, Revision 116 Part 1 - Design Principles". Retrieved 2012-06-14. "Our definition of the RNG allows implementation of a Pseudo Random Number Generator (PRNG) algorithm. However, on devices where a hardware source of entropy is available, a PRNG need not be implemented. This specification refers to both RNG and PRNG implementations as the RNG mechanism. There is no need to distinguish between the two at the TCG specification level."
- "tspi_data_bind(3) - Encrypts data blob". Trusted Computing Group. Retrieved 2009-10-27.
- "TPM Main Specification Level 2 Version 1.2, Revision 116 Part 3 - Commands". Trusted Computing Group. Retrieved 2011-06-22.
- James Greene (2012). "Intel Trusted Execution Technology: White Paper" (PDF). Intel Corporation. Retrieved 2013-12-18.
- Instruction 8500.01. US Department of Defense. March 14, 2014. p. 43.
- "LUKS support for storing keys in TPM NVRAM". github.com. 2013. Retrieved 2013.
- "FAQ", True crypt.
- Autonomic and Trusted Computing: 4th International Conference, ATC 2007. Books.google.com. Retrieved 2014-05-31.
- Pearson, Siani; Balacheff, Boris (2002). Trusted computing platforms: TCPA technology in context. Prentice Hall. ISBN 0-13-009220-7.
- "SetPhysicalPresenceRequest Method of the Win32_Tpm Class". Microsoft. Retrieved 2009-06-12.
- Infineon TPM
- ITE TPM
- "Trusted Platform Module Library; Part 1: Architecture" (PDF). Trusted Computing Group. 2014-03-13. Retrieved 2014-09-02.
- "Section 23: Enhanced Authorization (EA) Commands" (PDF). "Trusted Platform Module Library; Part 3: Commands". Trusted Computing Group. 2014-03-13. Retrieved 2014-09-02.
- Stallman, Richard Matthew, "Can You Trust Your Computer", Project GNU, Philosophy, Free Software Foundation
- Amit Singh: Trusted Computing for Mac OS X
- Your Laptop Data Is Not Safe. So Fix It.
- "TPM. Complete protection for peace of mind".
- "Oracle Solaris and Oracle SPARC T4 Servers— Engineered Together for Enterprise Cloud Deployments". Oracle Corporation. Retrieved 2012-10-12.
- "tpmadm manpage". Oracle Corporation. Retrieved 2012-10-12.
- "Chromebook security: browsing more securely". Google Chrome Blog. Retrieved 2013-04-07.
- "Security and the Virtualization Layer", VMware.com
- "Enabling Intel TXT on Dell PowerEdge Servers with VMware ESXi", Dell.com
- "Replacing Vulnerable Software with Secure Hardware: The Trusted Platform Module (TPM) and How to Use It in the Enterprise" (PDF). trustedcomputinggroup.org. 2008. Retrieved 2014-06-07.
- "NetXtreme Gigabit Ethernet Controller with Integrated TPM1.2 for Desktops". broadcom.com. 2009-05-06. Retrieved 2014-06-07.
- Trusted Computing Group (and specifications)
- LWN: OLS: Linux and trusted computing
- GRC podcast: Trusted Platform Module (TPM content starts at 24:30)
- TPM Setup (for Mac OS X)
- Trusted Computing Group Bulletin on the Security of the Trusted Platform Module (TPM) February 2008
- Take Control of TCPA
- TPM Reset Attack
- White Paper by Intel Corporation and IBM Corporation Trusted Platforms
- A short introduction to TPMs, by Matthew Garrett
- Trusted Infrastructure "101", by Andrew Martin
- Using the TPM: Machine Authentication and Attestation
- A Root of Trust for Measurement: Mitigating the Lying Endpoint Problem of TNC