03 - Verification Protocol

This protocol defines how digital services can locally verify agent identity attestations against the current state of the Open Agent Trust Registry.

Protocol

Target performance: Steps 1-14 must be optimized to complete in <1ms on commodity hardware.

The primary advantage of this architecture is No network calls per request. Pure local computation.

Step 1: Parse the incoming JWS attestation token.
Step 2: Extract the `iss` (issuer_id) and `kid` (Key ID) from the JWS header.

Step 3: Look up the `issuer_id` within the local copy of the registry manifest.
Step 4: If the issuer is not found → REJECT (Unknown Issuer).
Step 5: If the issuer `status` is "suspended" → REJECT (Issuer Suspended).
         If the issuer `status` is "revoked" → REJECT (Issuer Revoked).

Step 6: Locate the public key in the `public_keys` array matching the extracted `kid`.
Step 7: If the key is not found → REJECT (Unknown Key).
Step 8: If the key `status` is "revoked" → REJECT.
Step 9: If the key `status` is "deprecated":
  9a: If `deprecated_at` is not set → REJECT (data integrity error).
  9b: If current_time - `deprecated_at` > 90 days (grace period, see 04-key-rotation.md) → REJECT (Grace Period Expired).
  9c: Otherwise → ACCEPT but log a warning that key rotation is imminent.
Step 10: If the key is expired (current time > `expires_at`) → REJECT.

Step 11: Verify the JWS signature using the located public key.
Step 12: If the signature is mathematically invalid → REJECT.

Step 13: Check the attestation claims:
         - `aud` (Audience): Matches this specific service's origin.
         - `exp` (Expiry): > current time (The token itself is not expired).
         - `nonce` (If applicable): Matches the specific nonce the service previously issued (to prevent replay within the same session).

Step 14: If all checks pass → ACCEPT 
         The service may safely extract the `scope` and `constraints` arrays to authorize the agent's actions on behalf of the pseudonymized user.

Attestation Replay Protections

• Cross-Service Replay: The aud claim unequivocally binds the attestation to a specific service origin. Service B rejects attestations where aud doesn't match its own domain, mitigating stolen tokens.
• Intra-Service Replay: Services can enforce a nonce check, ensuring an intercepted token cannot be re-presented to the same service at a later date. Validated attestations should explicitly include their short TTL.