Trusted Execution Technology

Trusted Execution Technology (TXT) is the name of a computer hardware technology associated with a so-called Trusted platform module (TPM). Formerly known as LaGrande Technology, it is a key component of Intel's initiative of "safer computing".

Intel Trusted Execution Technology (Intel TXT) is a hardware extension to some of Intel's microprocessors and respective chipsets, intended to provide computer users or system providers with a higher level of trust and control over computer systems. Intel claims that it will be very useful, especially in the business world, as a way to defend against software-based attacks aimed at stealing sensitive information. Although commonly advertised by Intel as security technology, the Free Software Foundation explains how it can also be used to enable development of more advanced, tamper-resistant forms of DRM, and can be used to achieve vendor lock-in.

It consists of a series of hardware enhancements, to allow for the creation of multiple separated execution environments, or partitions. One component is called the TPM (Trusted platform module), which allows for secure key generation and storage, and authenticated access to data encrypted by this key. Note, however, that the private key stored in the TPM is generally not available to the owner of the machine, and never leaves the chip under normal operation. The TPM additionally provides for a means of remote assurance of a machine's security state.

This technology is coupled with VT-d (Intel Virtualization Technology for Directed I/O) which, among other things, protects certain areas related to TXT from DMA.

TXT provides hardware and firmware security against software intended attacks. The TPM (Trusted Platform Module) that manages Trusted Platform requests generates keys and certificates for private environments (application or service space) and manages the machine trust state, that will allow for example, the local user (or even a remote party) to check the security on a workstation with a higher level of confidence, using, for example, the Remote Attestation Protocol.

TXT Architecture

The Intel TXT protects five points on a server/client machine:

• The processor: With a private environment for applications, so that the hardware resources (such as memory pools) are locked to the calling applications and cannot be accessed whether for read or write by any other process running on the platform (notably including privileged processes such as the operating system core itself).
• The chipset: Enforces security on the main board by controlling more accurately the memory management policy, enhancements to memory access mechanisms, channel control mechanisms for hardware extensions (user I/O, Graphics, etc.) and secure interface to the TPM
• The user input: Protection states over keyboard and mouse, allowing users to interact with trusted platform applications, without the risk of being compromised by being observed by other running software
• The display interface: This feature enables trusted platform applications to send display data to specific context (a window for example) memory buffer, preventing running software from accessing the transmitted information
• The TPM device: Helps the system startup (in conjunction with ROM-BIOS startup routines), manages the keys, and provides attestations for the system's trusted status

Limitations

Invisible Things Lab presented an attack on TXT that involves compromising the SMM, demonstrating that TXT cannot be more secure than SRTM (Static Root of Trust Measurement): If an attacker can compromise the BIOS, then the attacker can also bypass TXT.

Parallel Technologies

The TXT is commercially distributed with another technology, Intel vPro. The VT-d provides hardware remote security, protecting hardware, storage and communications, adding another security level against software attacks.

VT-d is an environment model that shares hardware resources using I/O virtualization. This can then allow control over each process's access to resources without using reprobative exclusive access methods. Certain aspects of VT-d are also used to protect areas of memory from DMA access whilst in TXT mode.

Availability

Intel TXT requires specific support in the processor and the chipset. Furthermore, there has to be a TPM chip present on the motherboard, usually connected to the low pincount (LPC) bus. The chipsets implementing TXT are Q33, Q35, X38, Q43, Q45, GM45, GS45 and PM45. Some of the -4x range of chipsets include an integrated TPM called iTPM (implemented via a special ARC4 RISC CPU integrated into the chipset, also implementing some of Intel's Active Management Technologies (AMT)), removing the need for a TPM chip on the motherboard. However, note that the G41, G43, G45, P43, P45 - whilst supporting TXT - don't include the integrated TPM and thus require an onboard TPM for TXT to be usable. Intel's latest Q57 chipset also support TXT, but doesn't have the integrated TPM in the chipset (and hence requires the motherboard to provide the TPM).

Not all Intel processors support Intel TXT. The only way to find out is to consult the marketing material for each CPU, available on Intel's website.

CPUs supporting TXT contain special registers that make it possible to see if a TXT-compliant chipset was detected.

Intel has also released Trusted Boot (tboot) an Open source, pre-kernel/VMM module that uses Intel Trusted Execution Technology that adds the capability to verify the Xen Virtual Machine Monitor (VMM) launch using Dynamic Root of Trust Measurement (DRTM).

See also

• Trusted Computing
• Trusted Computing Group

External links

• Intel Trusted Execution Technology
• Trusted Execution Technology Overview
• Trusted Execution Technology Architectural Overview
• Intel Trusted Execution Technology Software Development Guide
• Intel Virtualization Technology
• GlobalPlatform white paper on standardized TEE