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Appendix B Glossary

NIST platform security: roots of trust, firmware and secure enclaves SP 800-147
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Title

Glossary

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Selected terms used in the publication are defined below.

Basic Input/Output System (BIOS): In this publication, refers collectively to boot firmware based on the conventional BIOS, Extensible Firmware Interface (EFI), and the Unified Extensible Firmware Interface (UEFI).

Conventional BIOS: Legacy boot firmware used in many x86-compatible computer systems. Also known as the legacy BIOS.

Core Root of Trust for Measurement (CRTM): The first piece of BIOS code that executes on the main processor during the boot process. On a system with a Trusted Platform Module the CRTM is implicitly trusted to bootstrap the process of building a measurement chain for subsequent attestation of other firmware and software that is executed on the computer system.

Extensible Firmware Interface (EFI): A specification for the interface between the operating system and the platform firmware. Version 1.10 of the EFI specifications was the final version of the EFI specifications, and subsequent revisions made by the Unified EFI Forum are part of the UEFI specifications.

Firmware: Software that is included in read-only memory (ROM).

Option ROM: Firmware that is called by the system BIOS. Option ROMs include BIOS firmware on add-on cards (e.g., video card, hard drive controller, network card) as well as modules which extend the capabilities of the system BIOS.

Protected Mode: An operational mode found in x86-compatible processors with hardware support for memory protection, virtual memory, and multitasking.

Real Mode: A legacy high-privilege operating mode in x86-compatible processors.

System Management Mode (SMM): A high-privilege operating mode found in x86-compatible processors used for low-level system management functions. System Management Mode is only entered after the system generates a System Management Interrupt and only executes code from a segregated block of memory.

System Flash Memory: The non-volatile storage location of system BIOS, typically in electronically erasable programmable read-only memory (EEPROM) flash memory on the motherboard. While system flash memory is a technology-specific term, guidelines in this document referring to the system flash memory are intended to apply to any non-volatile storage medium containing the system BIOS.

Trusted Platform Module (TPM): A tamper-resistant integrated circuit built into some computer motherboards that can perform cryptographic operations (including key generation) and protect small amounts of sensitive information, such as passwords and cryptographic keys.

Unified Extensible Firmware Interface (UEFI): A possible replacement for the conventional BIOS that is becoming widely deployed in new x86-based computer systems. The UEFI specifications were preceded by the EFI specifications.