Chain of Trust

A Chain of Trust is a hierarchical verification process that ensures each layer of a system can be trusted before control is handed off to the next. It creates an unbroken sequence of trusted components, starting from the hardware and extending up through the entire software stack.

In SecretVM, this process is anchored in cryptographic measurements—hashes of each component—that are stored in secure hardware registers such as MRTD and RTMR0–RTMR3. These measurements are later used to generate an attestation report, allowing external verifiers to confirm the VM’s integrity.

SecretVM Boot-Time Chain of Trust

The following sequence outlines how SecretVM establishes trust, step by step:

1. SEAM Module (Secure Arbitration Mode)

   • Measures the firmware into the MRTD register.

   • Transfers control to the firmware layer.

2. Firmware

   • Measures key system configurations into RTMR0, including:

     • Configuration Firmware Volume (CFV)

     • Trusted Domain Hand-Off Blocks (TDHOB)

     • ACPI tables

   • Measures the OS kernel into RTMR1.

   • Measures the initramfs (Initial RAM Filesystem) and kernel command line into RTMR2.

   • Transfers control to the initramfs.

3. Initramfs

   • Runs an initialization script that:

     • Measures the Root File System (RootFS) and docker-compose.yaml into RTMR3.

   • Transfers control to the RootFS.

4. Root File System

   • Launches startup services for SecretVM, including:

     • Generating (or restoring) a TLS certificate for the machine.

     • Producing a GPU attestation quote if a GPU is attached.

     • Storing the GPU nonce and TLS certificate fingerprint into the reportdata field of the Attestation Report.

     • Starting the Attestation Service.

     • Launching the containerized workload defined by docker-compose.yaml.

This layered verification process ensures that every stage of SecretVM’s initialization is cryptographically measured, trusted, and verifiable. The final attestation report reflects the complete trust state of the VM, enabling secure key provisioning and external validation.