Intel Trusted Execution Technology (Intel TXT, formerly known as LaGrande Technology) is a computer hardware technology of which the primary goals are: Intel TXT uses a Trusted Platform Module (TPM) and cryptographic techniques to provide measurements of software and platform components so that system software as well as local and remote management applications may use those measurements to make trust decisions.
It defends against software-based attacks aimed at stealing sensitive information by corrupting system or BIOS code, or modifying the platform's configuration.
The Trusted Platform Module (TPM) as specified by the TCG provides many security functions including special registers (called Platform Configuration Registers – PCRs) which hold various measurements in a shielded location in a manner that prevents spoofing.
The PCR extension mechanism is crucial to establishing a Chain of trust in layers of software (see below).
The BIOS measures additional components into PCRs as follows: The dynamic chain of trust starts when the operating system invokes a special security instruction, which resets dynamic PCRs (PCR17–22) to their default value and starts the measured launch.
The dynamic PCRs contain measurement of: The technology also provides a more secure way for the operating system to initialize the platform.
Additionally, those values can be used to identify the execution environment (the particular BIOS version, OS level, configuration, etc.)
Open-source projects also utilize the TXT functionality; for example, tboot provides a TXT-based integrity system for the Linux kernel and Xen hypervisor.