§ Decentralized Identity Interop Profile v4

Profile Status: Draft

Latest Draft: https://FIDEScommunity.github.io/DIIP

Editors:: Eelco Klaver (Credenco); Harmen van der Kooij (FIDES Labs); Niels Klomp (Sphereon); Niels van Dijk (SURF); Samuel Rinnetmäki (Findynet); Timo Glastra (Animo Solutions)
Contributors and previous editors:: Adam Eunson (Auvo); Jelle Millenaar (Impierce Technologies); Maaike van Leuken (TNO); Thierry Thevenet (Talao)

§ Abstract

The Decentralized Identity Interop Profile, or DIIP for short, defines requirements against existing specifications to enable the interoperable issuance and presentation of Digital Credentials between Issuers, Wallets, and Verifiers.

Purpose	Specification
Credential format	W3C VCDM (20 March 2025) and SD-JWT VC (draft 08)
Signature scheme	SD-JWT as specified in VC-JOSE-COSE (20 March 2025) and SD-JWT VC (draft 08)
Signature algorithm	ES256 (RFC 7518 May 2015)
Identifying Issuers, Holders, and Verifiers	did:jwk (Commit 8137ac4, Apr 14 2022) and did:web (31 July 2024)
Issuance protocol	OpenID for Verifiable Credentials Issuance (OID4VCI) (Draft 15)
Presentation protocol	OpenID for Verifiable Presentations (OID4VP) (Draft 28)
Revocation mechanism	IETF Token Status List (Draft 10, 2025-04-16)

The Normative References section links to the versions of specifications that DIIP-compliant implementations must support.

This document is not a specification but a profile. It outlines existing specifications required for implementations to interoperate with each other. It also clarifies mandatory features for the options mentioned in the referenced specifications.

The main objective of this profile is to allow for easy adoption and use the minimum amount of functionality for a working Digital Credential ecosystem.

§ Status of This Document

The Decentralized Identity Interop Profile v4 is a DRAFT specification under development.

The latest published DIIP profile can be found at https://FIDEScommunity.github.io/DIIP/latest.html

§ Audience

The audience of this document includes organisations aiming to issue or verify Digital Credentials, as well as the implementers of Digital Credential solutions (Wallets and Agents).

§ Development of the DIIP profile

Participate:: GitHub repo; File a bug; Commit history

The development of this interoperability profile is a collaborative process. Anyone can suggest new specifications and restrictions. The suggestions are reviewed by the community, and decisions are made through discussions.

Feel free to join the FIDES Community Discord to participate in the discussions.

There are also monthly DIIP meetings. Contact Harmen van der Kooij if you want to be invited to the meetings.

The authors inted to release new versions of the DIIP profile twice a year.

Some plans and ideas for the next version are documented in the Appendix A: Future Directions.

§ Structure of this Document

The Goals section explains the design of the DIIP profile.

The Profile section defines the requirements for compliant solutions and explains the choices.

The References section defines the specifications and their versions.

The Terminology section explains the key terms used in this profile.

§ Goals

The W3C VCDM specification defines a data model for Digital Credentials but does not prescribe standards for transport protocol, key management, authentication, query language, etc.

The (OID4VCI) and (OID4VP) protocols define the interaction between Wallets and Agents but don’t specify a data model or a credential format.

This interoperability profile makes selections by combining a set of specifications. It chooses standards for credential format, signature algorithm, identifying actors, and issuance and presentation protocols. Instead of saying, “We use W3C VCDM credentials signed with VC-JOSE-COSE using ES256 as the signature algorithm, OID4VCI as the issuance protocol, and OID4VP as the presentation protocol, and OpenID Federation for trust establishment,” you can just say, “We use DIIP.”

In addition, the DIIP profile makes selections within the specifications. When a standard allows multiple ways of implementing something, DIIP makes one of those ways mandatory. As an implementer, you don’t need to fully support all specifications to be DIIP-compliant. DIIP makes these choices to accelerate adoption and interoperability – defining the minimum required functionality.

DIIP does not exclude anything. For example, when DIIP says that compliant implementations MUST support did:jwk as an identifier of the Issuers, Holders, and Verifiers, it doesn’t say that other identifiers cannot be used. The Wallets and Agents can support other identifiers as well and still be DIIP-compliant.

Trust ecosystems can also easily extend DIIP by saying, “We use the DIIP profile and allow mDocs as an additional credential format.” They can also switch requirements by saying, “We use the DIIP profile but use VC-DATA-INTEGRITY as an embedded proof mechanism.”

The design goal for DIIP is to ensure interoperability between Agents and Wallets in cases where device binding of Digital Credentials is not required and the Wallet doesn’t need to be trusted. Issuing, holding, and presenting certifications, diplomas, licenses, permits, etc., fit into the scope of DIIP. Using a Wallet for strong customer authentication or for sharing Person Identification Data (PID) is out of DIIP’s scope, and you should look into HAIP instead.

§ Relationship to eIDAS regulation and HAIP profile

In the context of the European eIDAS regulation (eIDAS) and its Architecture and Reference Framework (ARF), the DIIP profile is a profile for “regular” digital credentials, “non-qualified electronic attestations of attributes”.

Digital Agents and Wallets may support both DIIP and the OpenID4VC High Assurance Interoperability Profile (HAIP). HAIP is targeted for high-assurance use cases where it is important to bind the credentials to the Holder's private key (device binding). DIIP is the profile for other use cases.

The standards used in the DIIP profile are the same ones that the ARF uses, but DIIP makes different choices to HAIP in some areas where OID4VCI and OID4VP provide optionality.

While DIIP is a standalone profile and enables interoperability on it’s own, it is designed to build upon and integrate with the EUDI wallet. Therefore, DIIP implementers who want to integrate with the EUDI Wallet should support HAIP and the implementation regulations issued by the European Commission.

§ Profile

In this section, we describe the interoperability profile.

§ Credential Format

The W3C Verifiable Credential Data Model (W3C VCDM) defines structure and vocabulary well suited for Digital Credentials in DIIP’s scope. For example, the Open Badges 3 credentials use W3C VCDM as the data format.

The SD-JWT-based Verifiable Credentials specification (SD-JWT VC) defines a credential format that are serialized in JSON Web Tokens (JWTs) and enable selective disclosure. SD-JWT VC is used as a credential format for person identification data (PID) in HAIP and ARF (in addition to mDocs).

W3C VCDM recommends using Securing Verifiable Credentials using JOSE and COSE (VC-JOSE-COSE) as an enveloping proof mechanism and Verifiable Credential Data Integrity 1.0 (VC-DATA-INTEGRITY) as an embedded proof mechanism.

To keep things as simple as possible, DIIP requires implementations to use SD-JWT as the mechanism to secure also W3C VCDM-based credentials.

Requirement: DIIP-compliant implementations MUST support both W3C VCDM and SD-JWT VC as a credential format.

Requirement: DIIP-compliant implementations MUST support Securing JSON-LD Verifiable Credentials with SD-JWT as specified in (VC-JOSE-COSE).

§ Signature Algorithm

There are many key types and signature methods used with JWTs. The table below lists some of the most common ones that implementations may want to support.

Key types	Signature Method
Ed25519	ECDSA
(x25519)
Secp256r1	ES256
Secp256k1	ES256K
RSA	RSA256

However, the DIIP profile does not force everyone to support everything, but chooses one key type Secp256r1 and one signature method ES256 that all implementations must support.

Requirement: DIIP-compliant implementations MUST support ES256 (ECDSA using Secp256r1 curve and SHA-256 message digest algorithm).

§ Identifiers

DIIP prefers decentralized identifiers (DIDs) as identifiers. An entity identified by a DID publishes a DID Document, which can contain useful metadata about the entity, e.g., various endpoints. There are many DID Methods defined. The DIIP profile requires support for two of them: did:jwk and did:web. In many use cases, organizations are identified by did:web, and the natural persons are identified by did:jwk.

Requirement: DIIP-compliant implementations MUST support did:jwk and did:web as the identifiers of the Issuers, Holders, and Verifiers.

§ Trust Establishment

Signatures in Digital Credentials can be used to verify that the content of a credential has not been tampered with. But anyone can sign a credential and put anything in the issuer field. Digital Credential ecosystems require that there is a way for a Verifier to check who the Issuer or a Digital Credential is. Equally, a user might want to be informed about the trustworthiness of a Verifier before choosing to release credentials.

The DIIP v4 profile doesn’t require compliant implementations to support any trust establishment mechanism.

§ Issuance

The issuance of Digital Credentials from the Issuer to the Holder's Wallet is done along the OID4VCI specification. Other protocols exist, but OID4VCI is very broadly supported and also required by HAIP.

§ OID4VCI

OpenID for Verifiable Credential Issuance (OID4VCI) defines an API for the issuance of Digital Credentials. OID4VCI issuance flow variations leave room for optionality.

In many situations, Digital Credentials are issued on the Issuer's online service (website). This online service may have already authenticated and authorized the user before displaying the credential offer. Another authentication or authorization is not needed in those situations.

Authorization Code Flow provides a more advanced way of implementing credential issuance. Proof Key for Code Exchange (PKCE) defines a way to mitigate against authorization code interception attack. Pushed authorization request (PAR) allows clients to push the payload of an authorization request directly to the authorization server. These features may be needed in higher assurance use cases or for protecting privacy.

Requirement: DIIP-compliant implementations MUST support both Pre-Authorized Code Flow and Authorization Code Flow.

Requirement: DIIP-compliant implementations MUST support the Transaction Code when using Pre-Authorized Code Flow.

Requirement: DIIP-compliant implementations MUST support the trust_chain claim when using Pre-Authorized Code Flow.

Requirement: DIIP-compliant implementations MUST NOT assume the Authorization Server is on the same domain as the Issuer.

Requirement: DIIP-compliant implementations MUST support PKCE and PAR.

It should be noted that various Security Considerations have been described in the OID4VCI specification with respect to implementing Pre-Authorized Code Flow. Parties implementing DIIP are strongly suggested to implement mitigating measures, like the use of a Transaction Code.

OID4VCI defines Wallet-initiated and Issuer-initiated flows. Wallet-initiated means that the Wallet can start the flow without any activity from the Issuer. The Issuer-initiated flow seems to be more common in many use cases and seems to be supported more widely. It also aligns better with the use cases where the Holder is authenticated and authorized in an online service before the credential offer is created and shown.

Requirement: DIIP-compliant implementations MUST support the Issuer-initiated flow.

OID4VCI defines Same-device and Cross-device Credential Offer. People should be able to use both their desktop browser and their mobile device’s browser when interacting with the Issuer's online service.

Requirement: DIIP-compliant implementations MUST support both Same-device and Cross-device Credential Offer.

OID4VCI defines Immediate and Deferred flows. Deferred is more complex to implement and not required in most use cases.

Requirement: DIIP-compliant implementations MUST support the Immediate flow.

OID4VCI defines proof types jwt, ldp_vp, and attestation for binding the issued credential to the identifier of the end-user possessing that credential. DIIP requires compliant implementations to support did:jwk as an identifier. Thus, in cases where cryptographic holder-binding is needed, implementations should be able to bind a credential to the holder’s did:jwk.

Requirement: DIIP-compliant implementations MUST support The jwt proof type with a did:jwk or did:web as the value of the kid element.

§ Presentation

The presentation of claims from the Holder's Wallet to the Verifier is done along the OID4VP. Other protocols exist, but OID4VP is very broadly supported and also required by HAIP.

§ OID4VP

Using OID4VP, the Holders can also present cryptographically verifiable claims issued by third-party Issuers, such that the Verifier can place trust in those Issuers instead of the subject (Holder).

OID4VP supports scenarios where the Authorization Request is sent both when the Verifier is interacting with the Holder using the device that is the same or different from the device on which requested Digital Credentials are stored.

Requirement: DIIP-compliant implementations MUST support both Same-device Flow and Cross-device Flow.

According to OID4VP, rhe Verifier may send an Authorization Request using either of these 3 options:

Passing as URL with encoded parameters
Passing a request object as value
Passing a request object by reference

DIIP only requires support for the last option. Requirement: DIIP-compliant implementations MUST support passing the Authorization Request object by reference.

OID4VP defines two values for the request_uri_method in the Authorization Request: get and post. DIIP requires support for only the get method.

Requirement: DIIP-compliant implementations MUST support the get value for the request_uri_method in the Authorization Request.

OID4VP defines many Client Identifier Schemes. One way to identify Verifiers is through OpenID Federation. Since DIIP uses DIDs, it is natural to require support for the corresponding Client Identifier Scheme.

Requirement: DIIP-compliant implementations MUST support the did Client Identifier Scheme.

The following features of OID4VP are not required by this version of the DIIP profile:

Presentations Without Holder Binding Proofs (section 5.3, requirements for the state parameter)
Verifier Attestations (section 5.11)
SIOPv2 (section 8, Response Type value vp_token id_token and scope containing openid)
Encrypted Responses (section 8.3)
Transaction Data (section 8.4)
Digital Credentials API (Appendix A)

§ Validity and Revocation Algorithm

Expiration algorithms using validFrom and validUntil are a powerful mechanism to establish the validity of credentials. Evaluating the expiration of a credential is much more efficient than using revocation mechanisms. While the absence of validFrom and validUntil would suggest a credential is considered valid indefinitely, it is recommended that all implementations set validity expiration whenever possible to allow for clear communication to Holders and Verifiers.

Requirement: DIIP-compliant implementations MUST support checking the validity status of a Digital Credential using validFrom and validUntil when they are specified.

The IETF Token Status List defines a mechanism, data structures, and processing rules for representing the status of Digital Credentials (and other “Tokens”). The statuses of Tokens are conveyed via a bit array in the Status List. The Status List is embedded in a Status List Token.

The Bitstring Status List is based on the same idea as the IETF Token Status List and is simpler to implement since it doesn’t require signing of the status list. The IETF Token Status List may gain more support since it is recommended by HAIP.

Requirement: DIIP-compliant implementations MUST support IETF Token Status List as a status list mechanism.

§ Terminology

This section consolidates in one place common terms used across open standards that this profile consists of. For the details of these, as well as other useful terms, see the text within each of the specifications listed in References.

Agent: A software application or component that an Issuer uses to issue Digital Credentials or that a Verifier uses to request and verify them.
Holder: An entity that possesses or holds Digital Credentials and can present them to Verifiers.
DID: Decentralized Identifier as defined in DID Core.
Issuer: A role an entity can perform by asserting claims about one or more subjects, creating a Digital Credential from these claims, and transmitting the Digital Credential to a Holder, as defined in W3C VCDM.
Digital Credential: A set of one or more Claims made by an Issuer that is tamper-evident and has authorship that can be cryptographically verified.

Verifier: An entity that requests and receives one or more Digital Credentials for processing.
Wallet: A software application or component that receives, stores, presents, and manages credentials and key material of an entity.

§ References

§ Normative References

did:jwk: did:jwk Method Specification. Status: Draft.
did:web: did:web Method Specification. Status: Unofficial working group draft.
ES256: ECDSA using P-256 (Secp256r1) and SHA-256 as specified in RFC 7518 JSON Web Algorithms (JWA). Status: RFC - Proposed Standard.
IETF Token Status List: Token Status List - draft 10. Status: Internet-Draft.
OID4VCI: OpenID for Verifiable Credential Issuance - draft 15. Status: Second Implementer’s Draft.
OID4VP: OpenID for Verifiable Presentations - draft 28. Status: Third Implementer’s Draft.
PAR: RFC 9126 Pushed Authorization Requests. Status: RFC - Proposed Standard.
PKCE: RFC 7636 Proof Key for Code Exchange by OAuth Public Clients. Status: RFC - Proposed Standard.
SD-JWT VC: SD-JWT-based Verifiable Credentials (SD-JWT VC) - draft 08. Status: WG Document.
Secp256r1: Secp256r1 curve in RFC 5480 ECC SubjectPublicKeyInfo Format. Status: RFC - Proposed Standard.; This curve is called P-256 in RFC 7518 JSON Web Algorithms (JWA). Status: RFC - Proposed Standard.
W3C VCDM: Verifiable Credentials Data Model v2.0. Status: W3C Proposed Recommendation.
VC-JOSE-COSE: Securing Verifiable Credentials using JOSE and COSE. Status: W3C Proposed Recommendation.

§ Non-Normative References

ARF: Architecture and Reference Framework. Status: Draft.
Bitstring Status List: Bitstring Status List v1.0. Status: W3C Proposed Recommendation.
DID Core: Decentralized Identifiers (DIDs) v1.0. Status: W3C Recommendation.
eIDAS: Regulation (EU) No 910/2014 of the European Parliament and of the Council of 23 July 2014 on electronic identification and trust services for electronic transactions in the internal market and repealing Directive 1999/93/EC. Status: In force.
HAIP: OpenID4VC High Assurance Interoperability Profile. Status: Draft.
JWT: RFC 7519 JSON Web Token (JWT). Status: RFC - Proposed Standard.
Open Badges 3: Open Badges Specification, Spec Version 3.0, Document Version 1.2. Status: This document is made available for adoption by the public community at large.
VC-DATA-INTEGRITY: Verifiable Credential Data Integrity 1.0. Status: W3C Proposed Recommendation.

§ Appendix A: Future Directions

§ Credential Formats

A future version of DIIP may require support for SD-JWT VCLD defined in the draft 27 of OID4VP.

§ Identifiers

A near-future version of DIIP will probably require support for did:webvh instead of did:web.

§ Trust Establishment

A future version of the profile will likely refer to OpenID Federation. In OpenID Federation, Issuers and Verifiers publish their own Entity Configurations, which include pointers to Trust Anchors. These Trust Anchors are trusted third parties that publish Entity Statements that allow for verification of the identity and the roles of the organizations. The OIDF Wallet Architectures specification specifies how to use OpenID Federation with Wallets.

One way to use OpenID Federation is described here as a guidance for implementers.

Issuer Agents publish the Issuer's Entity Configurations as specified in OIDF Wallet Architectures. (Simplified explanation: sign the OID4VCI issuer metadata as a JWT and publish it in the .well-known path.)
Verifier Agents publishi the Verifier's Entity Configurations as specified in OIDF Wallet Architectures. (Simplified explanation: sign the OID4VP verifier metadata as a JWT and publish it in the .well-known path.)
If a Digital Credential contains a termsOfUse object with an attribute federations, a DIIP-compliant Wallet MUST warn the user before sharing Digital Credentials or Verifiable Presentations with a Verifier for which a trust chain cannot be resolved using the Trust Anchor in the value of the federations attribute.

§ Presentation

Note that the next OID4VP draft versions may require that the did Client Identifier Scheme be prefixed in the presentation request. See https://github.com/openid/OpenID4VP/pull/401.

If a new version of DIIP uses OpenID Federation as the trust infrastructure, it is natural to identify parties using the same protocol and require DIIP-compliant implementations to support the https Client Identifier Scheme in OID4VP.

§ Digital Credentials API

DC API is a new W3C specification. The next versions of the DIIP protocol will most likely require compliant solutions to support DC API. If DIIP v4 compliant implementations support DC API, they should try to use that for credential issuance and verification and fall back to custom URI schemes if required.

§ References

DC API: Digital Credentials. Status: Draft Community Group Report.
did:webvh: The did:webvh DID Method v0.5. Status: CURRENT STABLE.
OIDF Wallet Architectures: OpenID Federation Wallet Architectures 1.0 - draft 03. Status: Draft.
OpenID Federation: OpenID Federation 1.0 - draft 42. Status: draft.