CCA Evidence Verification

CCA Attestation Verification

Initialisation

Mandatory

• CPAK public key (pCPAK)
• Reference values for CCA platform software components
• Reference value for CCA platform configuration
• Reference value for CCA realm Initial measurement configuration

Optional

• CCA realm personalisation value
• CCA realm extensible measurements

Cryptographic Validation

1. Check signature on the platform token according to §4.4. of RFC9052, using pCPAK.
2. Extract RAK public key (pRAK) from realm token (Note: The pRAK is is encoded into the uncompressed form specified in SEC 1, Version 2.0, Section 2.3.3. To be used for verification it typically needs to be converted into an x, y pair.)
3. Check signature on the realm token according to §4.4. of RFC9052, using pRAK.
4. Check the cryptographic binding between the platform and realm tokens:
   1. Extract pRAK from realm token
   2. Extract pRAK's hash algorithm identifier from the realm token
   3. Hash pRAK using said hash algorithm
   4. Extract nonce from the platform token
   5. Check nonce is the same as the value computed in step 4.3

CCA RoT Lifecycle Check

1. Extract the CCA lifecycle claim from the platform token and ensure that it is "SECURED"

Mandatory Reference Values Checks

1. Match software component measurements claims from the platform token against the corresponding reference values
2. Match configuration claim from the platform token against the corresponding reference value
3. Match initial measurement from the realm token against the corresponding reference value

Optional Reference Values Checks

The following steps depend on realm author's choice to use optional features.

1. Match personalisation value claim in the realm token against the corresponding reference value
2. Match extensible measurements claim in the realm token against the corresponding reference value