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Platform Certificate

The Platform Certificate as defined in the TCG Platform Certificate Profile is "a signed statement describing characteristics of a platform that can affect the platform’s trustworthiness."

Platform Cert Pic

The Platform Certificate is created by the platform manufacturer, and serves as the definitive link between the identity of a specific platform and its internal security components (one or more Roots of Trust such as the TPM). The signature of the issuer (manufacturer) cryptographically binds the manufacturer, model, serial number, and a set of hardware components to that specific platform. The platform can be a server, desktop or laptop.

Component List

Inside the Platform Certificate is a Component List. This list typically includes:

  • Component Class: (e.g., CPU, TPM, NIC, Storage)
  • Manufacturer & Model: The specific identity of the part
  • Serial Numbers: Unique identifiers for each critical chip
  • Network Adapter MAC addresses: Unique identifiers for each integrated network controller
  • Measurements/Hashes: Cryptographic snapshots of firmware or hardware configurations

HBOM

Recently, the Hardware Bill of Materials (HBOM) has received significant attention due to the growing adoption of Zero Trust security principles. In a Zero Trust architecture, organizations must verify and understand the components that make up their systems; if the silicon and hardware components inside servers, vehicles, or medical devices are unknown, they cannot be fully trusted. An HBOM provides this visibility by documenting all physical components within a device, along with the supply chain origins of those parts.

While the HBOM offers visibility into all components, the Platform Certificate provides verification—it proves that a device has not been tampered with. The Platform Certificate focuses specifically on security-critical components, taking a subset of the HBOM and signing only the parts that are sensitive to system integrity.

Delta Platform Certificates

A Delta Platform Certificate is defined in the TCG Platform Certificate Profile. It is issued by an entity such as a system integrator or Value Added Reseller (VAR) when authorized changes are made to a platform that are not reflected in the original Base Platform Certificate. Examples include upgrading RAM, adding a GPU, or replacing a faulty network card.

The Delta Platform Certificate is cryptographically linked to the Base Platform Certificate and describes only the changes (the "deltas"). Together, the Base and Delta Certificates form a Platform Certificate Chain, representing the full, validated configuration of a device.

Key Fields in a Delta Certificate:

  • Base Certificate Reference: A pointer (usually a hash or serial number) to the original Base Platform Certificate
  • Component Status: For every item in the new component list, it specifies a status:
    • Added: A new physical component was installed
    • Removed: An existing component was taken out
    • Modified: An existing component was upgraded or reconfigured (e.g., firmware update)
  • Issuer: Usually the VAR, not the original manufacturer

Platform Certificate & Attestation

Attestation CAs, like HIRS, use the Platform Certificate Chain to verify a system's measured security attributes and physical components match the "golden standard" information found in the Platform Certificate. This ensures the hardware has not been tampered with before an Attestation Certificate is issued.