AI attestation, explained

“Attestation” is an overloaded word. Three different communities use it for three different things, and conflating them causes real confusion in AI procurement and security reviews. This page disambiguates — and pins down what OVERT means by it.

Three kinds of attestation

Kind	Proves	Examples	When
Hardware / TEE attestation	which code is running in a trusted enclave	Intel SGX/TDX, AMD SEV, TCG/TPM, Fortanix, RFC 9334	at the silicon/boot layer
Build / supply-chain attestation	how an artifact was built and by whom	Sigstore, SLSA, in-toto, model cards/signing	before deployment
Runtime governance attestation	what a deployed AI system actually did on a request	OVERT	on every governed decision

They are complementary, not competing. TEE attestation tells you the enclave is genuine. Supply-chain attestation tells you the model binary is the one you built. Neither tells you that, when a user asked your agent to delete a record, your governance policy denied it — and lets an auditor verify that later. That runtime-behavior gap is what OVERT fills.

What OVERT attestation specifically proves

An OVERT receipt is a tamper-evident record of a governance decision at runtime:

• It binds a specific decision (Permit / Deny / RequireApproval / Shadow, with a typed reason) to a moment in time.
• It is signed with Ed25519 over RFC 8785 canonical JSON and chained in an RFC 6962-shaped transparency log.
• It is non-egress: hashes and line-ranges only, never the prompt or response.
• It is independently verifiable — the assurance level (AAL-1…4) tells a relying party exactly how much to trust it.

Why this distinction matters in a security review

If a vendor says “we do AI attestation,” ask which kind. A TEE or model-signing answer does not address runtime behavior governance, and vice versa. OVERT is explicitly the runtime-behavior layer and crosswalks to the others rather than replacing them.

How the pieces fit

• The OVERT standard defines what runtime attestation must demonstrate.
• OVERT-as-Code lets you declare the governance whose execution gets attested.
• The runtime product produces the receipts; the verifier checks them.

Documentation is not evidence Why attestation beats screenshots and questionnaires.

Verify a proof Check an OVERT receipt yourself.

The conformance ladder AAL-1 through AAL-4, explained.