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DTG Core Credentials Specification (ToIP DTGWG)

Repo: github.com/trustoverip/dtgwg-cred-spec — normative spec, Version 1.0, Working Draft 01. Supporting materials and discussions: github.com/trustoverip/dtgwg-cred-tf.

The authoritative specification for the Decentralized Trust Graph credential family, maintained by the Trust over IP Foundation’s DTG Working Group Credentials Task Force. This is the definitive source for DTG credential semantics — what each credential type means, how it’s constructed, what proofs it supports, and how the wider trust graph composes from them. Implementations track this spec; where the wiki and the spec disagree, the spec wins.

In July 2026 the spec moved home and became a formal ToIP deliverable: the informal dtg.md v0.3 that lived in the task-force repo was migrated into the ToIP Spec-Up-T template in a new repo, dtgwg-cred-spec, as DTG Core Credentials V1.0 — Working Draft 01. It now follows the Linux Foundation JDF process — a sequence of numbered Working Drafts until the task force submits it for a vote as a Working Group Approved Deliverable. The old repo (dtgwg-cred-tf) deleted its copy of the spec in August (#38) and keeps only supporting materials (use_cases.md, witnessed_vrc_flow.md, links to the First Person Project whitepaper, VTC Bootstrapping Process, DTG Glossary) plus the discussions board; spec-specific issues go to the new repo. RFC 2119 key words are binding only in sections that open with “This section is normative.” — the Introduction, Terminology, Taxonomy and all Considerations sections are informative.

The wiki entity for the implementation that tracks this spec is dtg-credentials (0.2.0 tracks WD01); for the conceptual taxonomy it defines, see dtg-credentials-overview.

Contents

Spec-Up-T layout (specs.json → spec/), rendered to docs/:

  • header.md — title, Version 1.0 / Working Draft 01, editors (Alberto Leon, Brendan A. Miller — Harvard Applied Technology Lab; Geoff Turk, Martina Kolpondinos, Drummond Reed — First Person Project), IPR (CC BY 4.0, W3C patent mode, Apache 2.0)
  • intro.md — abstract (“six W3C Verifiable Credential types that create and annotate the nodes and edges of a DTG”), the three functional categories, a note that this version uses DIDs exclusively as its verifiable identifiers (X.509 / KERI AIDs possible later)
  • terms-and-definitions-intro.md + terms-definitions/*.md — ~50 glossary terms, one file each, imported from the DTG Glossary: the credential types, DID types, DTG node/edge/VID, and the VTA topology vocabulary (personal / community / local / cloud VTA, VTA networks, PNM, PNV, VTSP — see vta-topology), community roles (initiator, community trust anchor, PEP, IDVP/IDVC), relationship card, relationship invitation (OOBI)
  • body.md — the normative core, in narrative order: Taxonomy → W3C VC version support (v2.0 primary, v1.1 legacy) → Base Structure (incl. the new taskContext property) → Edge Credentials (VRC, VMC) → Invitation Credential (VIC) → Annotation Credentials (VPC, VWC, VEC) → Trust Task Context Binding → Supporting Concepts (PHC, Trust Registries, IDVC, ZK & Selective Disclosure) → Security / Privacy / Governance / I18N / Accessibility Considerations → Conformance → References
  • appendix.md — acknowledgements
  • Companion specs announced but not yet written: DTG Verifiable Data Structures (relationship card, agent card) and DTG Core Trust Task Protocols (offer / issue / request / present / revoke and the trust-task completion artifact taskContext refers to)

Wiki pages derived from this spec

Recent Development

The spec is at v1.0 Working Draft 01 in dtgwg-cred-spec; activity is per-PR. Entries before July 2026 refer to PRs in the old dtgwg-cred-tf repo.

dtgwg-cred-tf #38 — 2026-08-18 — old repo retires its copy of the spec

dtg.md removed; README points to dtgwg-cred-spec as the normative home and to its issue tracker for spec issues. use_cases.md and witnessed_vrc_flow.md (v0.2, non-normative) stay as supporting material; discussions remain in the old repo.

PR #14 — 2026-08-12 — VWC digest becomes REQUIRED, binding the credential to a specific edge

With only issuer, taskContext and credentialSubject.id required, a conforming VWC could attest merely that some activity involving the subject occurred during a trust task — not that a specific relationship edge was established. digest is promoted OPTIONAL → REQUIRED. New guidance: credentialSubject.id and taskContext identify only the observed party and the exchange, not the edge; a digest without the referenced VRC to hand is an opaque hash, so issuers and holders presenting a VWC as evidence of a specific edge SHOULD make the referenced VRC available alongside it. witnessContext stays OPTIONAL. Reflected in witness-credential.

PR #13 — 2026-08-06 — narrative ordering; status set to Working Draft 01

Taxonomy diagram flipped to left-to-right in the order VRC, VMC, VIC, VPC, VWC, VEC; the VWC section moved before VEC under Annotation Credentials; header status “Working Draft” → “Working Draft 01”. No normative text changed.

PR #7 — 2026-07-30 — implementation feedback from Keyring Wallet: VWC digest canonicalisation + per-direction witnessing

Two fixes driven by a real implementation (Keyring Wallet’s witness server): (a) v0.3 said the digest was “a multibase string (multihash + multibase)” while its example showed sha256:<hex> — contradictory and unimplementable. Now: the digest MUST be the SHA-256 of the credential’s JSON canonicalised with JCS (RFC 8785), encoded as the string sha256: followed by the lowercase hex digest. (b) Per-direction witnessing: a witnessed exchange of a complete edge is bidirectional — two VRCs, one each way, in a single witnessing event — so the witness SHOULD issue one VWC per direction, and in each VWC credentialSubject.id MUST be the DID of the issuer of the VRC being attested. Note the dtg-credentials crate (0.2.0) encodes the digest as multibase/multihash (z…, the W3C digestMultibase convention) instead — a flagged, unresolved divergence.

PR #3 — 2026-07-13 — migrate v0.3 into the Spec-Up-T template (Working Draft)

Beyond the re-templating, several substantive changes:

  • New normative section “Trust Task Context Binding” and a new base-structure property taskContext (the threadId of the trust-task exchange in which the credential was issued): OPTIONAL on all types, REQUIRED on VWC. A credential without taskContext MUST be interpretable standing alone; a verifier MUST NOT treat a taskContext-bearing credential as proof the associated task completed unless the matching outcome evidence is present and verified. Informative test: “true outside the exchange? → credential; only meaningful inside? → artifact.” See trust-task-context-binding.
  • W-DID dropped from the identifier taxonomy — the VWC issuer is “an M-DID, or the DID of a VTA acting according to VTC policy”; four official DTG identifier types remain (R-DID, M-DID, C-DID, P-DID). Reflected in did-types.
  • RCard section removed; the relationship card is a VDS, not a DTGCredential, and moves to the planned DTG Verifiable Data Structures spec (alongside a planned agent card). The category count accordingly drops four → three (VDS gone). Reflected in credential-categories, dtg-credentials-overview.
  • VWC purpose broadened (the witness may be a person or a VTA applying VTC witnessing policy — e.g. same-event presence, biometric liveness); VIC explicitly has two functional variants — VTC invitation and VTN invitation — distinguished by issuer/subject rules, not type strings; VPC purpose adds “control intentional correlation across relationships”.
  • New Security Considerations (7 items — incl. VIC replay: short validity, single-use at the accepting VTA/PEP), Privacy (2 → 6 items), Governance (4 — “whether a VMC qualifies as a PHC is a governance determination, not a schema property”), Conformance targets (issuers / holders / verifiers; no test suites yet), I18N/Accessibility stubs, normative/informative references.
  • ZKP text, PHC, trust registries, IDVC carried over unchanged in substance from v0.3 (post-#31/#33). ~50 glossary terms imported as Spec-Up-T definitions.

PR #2 / #1 — 2026-07-07/08 — repo created from the Spec-Up-T template; README for DTG Core Credentials V1.0

PR #33 — 2026-05-08 — Split VRC/VMC ZKP proofs into pairwise and community-anchored constructions

  • The old single “Zero-Knowledge Proof Requirements” subsection (under VRC) is replaced by two distinct constructions:
    • Pairwise ZKP (under VRC §5.1) — available to any two VRC holders, regardless of shared community membership; selectively discloses P-DIDs while hiding R-DIDs
    • Community-Anchored ZKP (under VMC §5.2) — requires both parties to hold VMCs from the same community; the three-part proof (VRC + VMC + same C-DID) is preserved but reframed as one option among several
  • Section 5 reordered: VRC (5.1) now precedes VMC (5.2)
  • Overview rewritten: DTG credentials are W3C-compliant VCs that MAY use standard presentation but SHOULD use ZKPs whenever privacy preservation is desired (citing Adler et al. 2024 — Personhood Credentials)
  • New guidance: implementations SHOULD make ZKP presentation the default
  • Privacy Considerations gained a “ZKPs by default” bullet
  • Reflected in zero-knowledge-proofs, relationship-credential, membership-credential, persona-credential, credential-categories, dtg-credentials-overview

PR #31 — 2026-04-30 — Bidirectional Edge Credentials

See also: dtg-credentials (the Rust implementation), dtg-credentials-overview (the credential taxonomy as currently in the wiki).

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