Specification overview

A one-page summary of what the WCM specification defines, for readers deciding whether to read the full text. Each layer below starts with what it does in plain words, then names the parts the specification pins down.

The full normative text (the binding rules) is SPEC.md (v0.15). WCM is four layers plus a public, append-only log. The machine-readable form of the manifest, and the test cases an implementation is checked against, are on the schema and conformance page.

Layer 1 - the manifest

A signed document saying exactly which model files may be released, and on what terms.

It records the weights_hash, the release terms, the release policy (assurance tier, required platforms and serving image, trusted-time source, memory fingerprint challenge), and custody details. The builder and the custodian sign it together, never the customer alone, and a group of national signers can be added.

Layer 2 - attestation-gated key release

The key goes out only after fresh hardware evidence passes every check.

The key broker (KBS) sends a one-time number (nonce). The enclave returns combined evidence: a signed report from the CPU's protected virtual machine and a separate GPU report, both tied to that number. The KBS releases the key only if every check passes: platform, assurance tier, serving-image status (preferring the current approved image), GPU measurement and the link between CPU and GPU, a memory fingerprint when the hardware owner is treated as hostile, and up-to-date revocation information.

Layer 3 - runtime custody (wipe-on-lapse)

The protected environment keeps the key only for a short window and must keep proving itself to hold on to it.

The enclave holds the key only for the attestation window and erases it if it does not pass the check again in time; the key is gone, not paused. This limits the worst case to one window against an operator who cannot fake the hardware check, as long as the clock can be trusted (trusted_time_source).

Layer 4 - derivative lineage

Fine-tuned copies keep a record that points back to the original.

A fine-tune produces a new weights_hash, with derived_from pointing at its parent and a rights_holder recording who owns what, forming a chain back to the original model.

Transparency (§3.7)

A public log that can only be added to, so nobody can quietly show different people different histories or hide a revocation.

It is an append-only Merkle log (RFC 9162) with signed tree heads, which makes that kind of double-dealing (equivocation) and suppressed revocations detectable.

Guarantee scope (§3.6) - read this

WCM does not claim that the chip alone keeps the key safe from someone who owns the bare machine and has done no physical hardening. That setup is out of scope on purpose. See Limitations.