Security-critical applications, such as cross-domain solutions (CDS), require a secure, trusted platform on which to execute, spanning software, firmware, and hardware. The lowest layer that the application interacts with directly is a trusted operating system (OS). Trust in the OS is dependent on two factors: its robustness from a security perspective, and assurance that the OS was both loaded and configured correctly and never tampered with. OS trust also depends partly on trusted pre-OS functionality, such as secure boot firmware that executes before the OS.