Threat model

The useful question about an evidence system is not what it proves but who it still requires you to trust.

Removed from the trust set

CooL, for record contents. You recompute every digest and signature yourself with a published verifier. We cannot alter a record you already hold.

CooL, for signing keys. Keys are derived inside the enclave from the measurement. There is no escrow — we have no copy to surrender, and no code path that would produce one.

The network. Verification makes zero network calls, and on the website that count is measured rather than claimed.

Still in the trust set

CooL, for log history. A transparency log signed only by its operator is tamper-evident against outsiders and not against the operator. Against a determined insider at CooL, today, the log alone is not sufficient. External witnesses close this and they are not built.

The hardware vendor. A TEE attestation roots in Intel's signing key. If you do not trust the vendor, attestation proves nothing to you. No design removes this.

Your own operators. CooL records what your people did. It does not prevent them doing it, and was never intended to.

Attacks and outcomes

| Attack | Outcome | |---|---| | Edit a record after sealing | binding and signature both fail | | Re-sign with a different key | signature fails against the pinned key | | Staple a quote from another image | attestation fails — the quote digest is inside the signature | | Redeploy from a patched image | A different key is derived; the old pin no longer verifies | | Drop a record from the log | inclusion fails for that record | | Rewrite log history | consistency fails between tree heads | | Insider at CooL rewrites the whole log | Not detected today. Needs witnesses. |

Failure model

Capture is asynchronous, out-of-band and fail-open. If CooL is unreachable your inference continues; events queue, and what cannot be queued is counted with the count itself written as a signed entry. Loss is recorded, never silent.

RA-TLS is the opposite direction: fail-closed toward the network. A measurement mismatch means the channel never opens and nothing is transmitted.