constellation/docs/proof-of-ownership.md

Proof of Ownership

A cluster owner needs a way to prove a cluster belongs to them, while a third-party needs to be able to verify the owner's claims. For that, the owner generates a private/public key pair.

During constellation init, the cluster will generate its own private/public key pair, and send back a signing request for the public key.

The signed public key is measured into a PCR, so the binding of the private/public key to the cluster can be verified through remote attestation.

The cluster is now able to sign data using its own private key.

A third-party can verify a cluster belongs to a specific person in three steps:

1. Verify the signature of data provided by the third-party and signed by the cluster

2. Verify the cluster's public key was signed by the owner

3. Verify the public key is measured into a PCR by validating the cluster's attestation statement

Workflow

1. Cluster owner generates a private/public key pair

2. The Constellation cluster generates its own private/public key pair and requests the owner to sign the public key during constellation init

3. Constellation measures the signed public key into PCR[11] (previously used for ownerID)

4. A third-party requests an attestation from the verification service, providing some data to be signed

5. The verification service signs the data using its private key

6. The verification service returns: attestation document + data signature + signed public key

7. The third-party verifies the public key signature using the owner's public key

8. The third-party calculates the expected PCR[11] using the signed public key and validates the attestation document

9. The data signature is verified, and if successful proving ownership of the cluster

Encoding

The signed public key measured into PCR[11] is DER encoded. TODO: Add exact encoding specification