During booting of a computing device, multiple security boundaries are generated. A security boundary refers to a manner of operation of a computing device or a portion of the computing device, with a program executing in one security boundary being prohibited from accessing data and programs in another security boundary. As part of booting the computing device measurements of (e.g., hash values or other identifications of) various modules loaded and executed as part of booting the computing device are maintained by a boot measurement system of the computing device. Additionally, as part of booting the computing device, a public/private key pair of one of the security boundaries is generated or otherwise obtained. The private key of the public/private key pair is provided to the one security boundary, and the public key of the public/private key pair is provided to the boot measurement system.