Topic starter
11/11/2026 6:05 pm
TL;DR: Wallet interoperability breaks when compliant implementations make different protocol choices, according to Hopae. Verifiers and issuers need conformance checks that reject invalid requests as reliably as they accept valid ones.
Editorial analysis by NHI Mgmt Group, based on content published by Hopae: “OpenID4VC and HAIP: Turning Interoperability from Hope into Verification”.
By the numbers:
- HAIP 1.0 reached final specification status on 24 December 2025, giving regulators a named interoperability profile to reference.
- OpenID4VP 1.0 plus HAIP 1.0 recorded a 98% pass rate, showing that conformance can be measured rather than assumed.
Key questions
Q: Why do verifiable credential wallets need conformance testing?
A: Verifiable credential wallets need conformance testing to prove they implement the required data formats, cryptographic checks, and protocol steps consistently.
Q: What is the difference between OpenID4VCI and OpenID4VP?
A: OpenID4VCI is the issuance flow for getting a verifiable credential into a wallet, while OpenID4VP is the presentation flow for sending a credential or proof from a wallet to a verifier.
Q: How does OpenID4VC interoperability fail between compliant implementations?
A: Interoperability fails when two implementations make different valid choices about credential formats, signing algorithms, request handling, or trust resolution.
Practitioner guidance
- Define a single wallet interoperability profile Lock down supported credential formats, response modes, signature algorithms, and key-resolution rules before implementation teams diverge on local preferences.
- Adopt specification-based conformance testing Test against the protocol specification and negative cases, not only against one partner implementation, so shared misunderstandings do not pass as success.
- Separate trust governance from protocol choice Treat issuer onboarding, verifier authorisation, and root-certificate governance as a distinct control plane rather than assuming the protocol profile covers it.
Bottom line: OpenID4VC interoperability fails most often when compliant implementations choose different allowed options, so profile governance matters as much as protocol design.
Glossary terms: OpenID4VC, OpenID4VCI, OpenID4VP, Verifiable Credentials (VCs)
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11/11/2026 6:06 pm
HAIP converts interoperability from a compatibility exercise into a governance control. Once a digital identity ecosystem allows many technically valid combinations, implementation differences become a policy problem rather than a coding problem. That is why profile-based standardisation matters for wallet ecosystems: it reduces the room for silent divergence and makes verification behaviour predictable. Practitioners should see the profile as a control for reducing trust ambiguity across issuers, wallets, and verifiers.
A question worth separating out:
Q: Where does interoperability testing stop covering digital identity wallets?
A: Interoperability testing stops at the defined wallet protocol and format boundary, so it does not cover the full user experience, business policy, trust framework rules, or every issuer and verifier implementation choice. It usually checks whether wallets can issue, store, present, and verify the agreed credential types and message flows.
👉 Read our full editorial: HAIP makes wallet interoperability a conformance test, not guesswork