A Verifiable-Credential Binding for AI Usage Preferences: Expressing Grants that Lift AIPREF Preferences

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Table of Contents

1. Introduction

The AI Preferences vocabulary [AIPREF-VOCAB] defines a machine-readable way to express preferences about how automated systems process a digital asset. Each usage category (for example, "train-ai") is assigned a value such as "allowed" or "disallowed". A preference of "train-ai=disallowed" is a standing statement of intent by a party with rights in the asset: a reservation.¶

Preferences describe a default posture toward the world. They do not express what a specific party has been permitted to do. When a rights holder does permit a specific use by a specific party -- under a license, a negotiated agreement, or otherwise -- there is at present no interoperable, verifiable way to express and check that grant. This produces three operational problems:¶

• a party acting on a permission cannot prove, to a third party, that it held that permission for a given asset on a given date;¶
• a rights holder that granted a permission cannot withdraw it in a way that downstream verifiers can observe; and¶
• a dispute over whether an asset was permitted for a use cannot be resolved on independently checkable evidence.¶

Informally: an AIPREF preference is the lock; what is missing is a verifiable key, and a receipt for it that survives inspection later. This document sketches that missing piece as a signed, revocable credential that sits on top of the AIPREF vocabulary rather than replacing it, and asks where such a mechanism belongs.¶

This document does not propose changes to the AIPREF vocabulary itself, nor does it assert that a preference is legally binding or that any particular use is or is not permitted absent a grant. Those questions are out of scope.¶

2. Relationship to the AIPREF Vocabulary

A grant references an AIPREF usage category by its label (for example "train-ai" from [AIPREF-VOCAB], or a category introduced through that document's vocabulary-extension mechanism). A grant is scoped to a tuple of (asset, category, grantee, validity period). A grant that asserts "allowed" for a category lifts a "disallowed" preference for that category for the named grantee only; it makes no statement about any other party.¶

Grants and preferences are therefore complementary layers. The preference is authored by the rights holder as a standing signal; the grant is a discrete, verifiable exception issued to a specific party. A verifier that observes both applies the grant in preference to the standing preference for the named grantee, and applies the standing preference otherwise.¶

This document does not require AIPREF to define any new category to carry grants. It observes only that a category value MAY be lifted, for a named grantee, by a grant that the grantee can present and any verifier can check.¶

Preferences and grants also differ in how they are distributed. AIPREF preferences are typically attached to content and expressed to the world -- for example through robots.txt or HTTP header fields -- as a broadcast, party-agnostic signal of a default posture. A grant is not distributed that way: it is a signed artifact bound to a named grantee, held and presented by that grantee (or retrieved by reference), and checkable by any verifier without being attached to the content or announced to the world. A grant therefore complements a content-attached preference rather than competing with it: the preference is the broadcast reservation; the grant is the verifiable, per-party exception.¶

3. Relationship to Bilateral Contracts

A grant is a unilateral artifact: it is signed by the grantor alone. A separate class of mechanism expresses a bilateral agreement -- an offer made and accepted, signed by both parties. VDAC [VDAC] is one such mechanism. Grants and bilateral contracts are complementary layers, and they compose: a contract MAY carry a grant as one of its terms.¶

A contract carries a grant by reference. It names the grant with a type token -- for example "verifiable-grant" -- whose meaning is the resolution-and-verification procedure of Section 5; it identifies the grant by the grant's resolvable identifier (Section 4.1); and it pins the specific artifact by a cryptographic digest of the credential as retrieved, expressed using the Digest Fields representation [RFC9530]. The contract layer establishes which document is carried; this document establishes whether it is valid, and as of when. The contract does not interpret the grant beyond resolving and hashing it; a receiver that can process a carried grant reference verifies it per Section 5, including revocation under the as-of-use rule (Section 6.1).¶

Revocation composes across the two layers without conflict. A bilateral contract, once signed, is an immutable record that an agreement was reached; revoking a grant carried within it does not un-sign the contract. The grant's own status list carries the revocation, which the contract references. A grant marked revoked is void from the time of revocation forward, while the fact that the contract was agreed remains true. The two layers answer different questions -- what was agreed, and whether a carried grant still applies -- and both remain independently checkable.¶

4. The Grant Credential

{
  "@context": ["https://www.w3.org/ns/credentials/v2"],
  "id": "https://publisher.example/grants/abc123",
  "type": ["VerifiableCredential", "AIUsageGrantCredential"],
  "issuer": "did:web:publisher.example",
  "validFrom": "2026-07-01T00:00:00Z",
  "validUntil": "2027-07-01T00:00:00Z",
  "credentialSubject": {
    "asset": {
      "id": "urn:asset:sha-256",
      "digest": "sha-256:0f7e...c19a"
    },
    "grantee": "did:web:ai-lab.example",
    "usage": [
      { "category": "train-ai", "value": "allowed" }
    ]
  },
  "credentialStatus": {
    "type": "BitstringStatusListEntry",
    "statusPurpose": "revocation",
    "statusListIndex": "94",
    "statusListCredential": "https://publisher.example/status/1"
  }
}

5. Verification Procedure

To act on a grant, a verifier:¶

1. resolves the issuer identifier to a public key (for "did:web", by fetching the DID document over HTTPS [DID-WEB]) and verifies the signature over the credential;¶
2. confirms the current time is within the validity period;¶
3. confirms the grant was not revoked as of the relevant time, by checking the referenced status list [BITSTRING] under the as-of-use rule (Section 6.1);¶
4. confirms the asset digest matches the content in question, and that the category and grantee match the use and party at hand.¶

If all checks pass, a valid grant exists for that (asset, category, grantee); the corresponding preference is lifted for that grantee. Verification requires no interaction with the grantor beyond fetching the (cacheable) issuer key and status list, and can be performed offline against cached copies.¶

6. Revocation

A grantor withdraws a grant by updating the referenced status list so that the grant's entry indicates revocation. Verifiers observe the change the next time they refresh the status list, bounded by their cache policy. Revocation lets a rights holder end a permission after issuance -- a property that a standing preference change alone cannot provide for permissions already relied upon. Revocation is monotonic: a status list using the "revocation" status purpose [BITSTRING] only ever moves a grant's entry from valid to revoked, never back.¶

7. Discussion and Open Questions

This document is a discussion starter. The mechanism in Section 4 is one candidate, not a final design. The author invites discussion of the following in particular:¶

• Venue. The AI Preferences Working Group has, to date, scoped mechanisms above the vocabulary -- attachment, transmission, grants, and identity -- out of its charter. On that reading, grants and related mechanisms are better progressed elsewhere; this document suggests the DISPATCH area as their home, and invites confirmation that this is the right venue.¶
• Should the AIPREF vocabulary define any hook that indicates a category value is conditional on, or may be lifted by, a grant -- or should grants remain entirely a separate layer, as sketched here?¶
• Is a Verifiable Credential the right container, or should a lighter or different encoding be preferred? This document uses VCs because they provide issuer identity, offline verification, and revocation as existing, interoperable building blocks, but does not assert they are the only viable choice.¶
• Grantee identity. A grant names its grantee by a resolvable identifier -- for example a "did:web" identifier. Where a grant is exercised through a bilateral contract (Section 3), binding the presenting party to the named grantee at request time is a function of that contract layer rather than of the grant itself. Whether a grant should additionally carry its own request-time binding is left open.¶

8. Security Considerations

A grant proves who issued it, when, and what was declared. It does not attest that the grantor holds the rights it purports to grant: anyone in possession of an asset can compute its digest and issue a self-asserted grant over it. A verifier therefore MUST evaluate whether it trusts the issuer for the asset in question; the signature establishes the issuer's identity and the integrity of the declaration, not the truth of the underlying claim. Mechanisms for establishing that an issuer is authoritative for an asset are out of scope for this document.¶

Because a grant identifies its asset by content digest and does not carry the content, presenting a grant does not disclose the asset. Verifiers MUST confirm the digest matches the content actually processed; a grant for one asset says nothing about another.¶

Revocation is only as timely as verifiers' status-list refresh policy; a verifier relying on a stale cache may act on a revoked grant. Grants SHOULD carry a validity period so that a lost or unreachable status list does not extend a grant indefinitely.¶

9. IANA Considerations

This document has no IANA actions. Should the mechanism advance, a registry for the credential "type" and any grant-specific fields would be considered at that time.¶

Author's Address