Cloned from launchpad blueprint https://blueprints.launchpad.net/ironic/+spec/trusted-bare-metal-boot.
Boot artifacts: firmware, operating system, and modules that it shall be loaded (provided as an image) shall be measured. If the measured values matched expect or known-good-values, the machine can be trusted. Trusted bare metal machines are ideal to launch OpenStack services such as Nova, Keystone etc in addition to be the perfect machines for cloud users who have security needs and do not not want to lose performance by way of virtualization.
Specification URL (additional information):