WIA
(Wallet Instance Attestation)
A Wallet Instance Attestation (WIA) is a signed JWT, issued by a Wallet Provider, that attests the integrity and authenticity of a specific Wallet Instance: the part of the wallet the User interacts with, usually an app on the User's device. It names the Wallet Solution, its version and its certification, and carries a revocation reference for the Wallet Instance. The ARF calls it one of the two Wallet Unit Attestation types, alongside the Key Attestation.
A Wallet Unit sends its WIA when it asks a PID Provider or Attestation Provider for a credential. The WIA is the wallet attestation from OpenID4VCI Appendix E, sent to the issuer's authorization server together with a proof that the wallet holds the WIA key. The issuer verifies the Wallet Provider's signature against the trust anchor the Commission publishes for that Wallet Provider, and checks that the Wallet Instance has not been revoked.
A WIA is sent for every credential, device-bound or not. For a device-bound credential the Wallet Unit also sends a Key Attestation, which describes the WSCA/WSCD or keystore that holds the new key.
A WIA is valid for less than 24 hours, so it reflects a recent integrity check rather than a one-time check at installation. It also states a revocation maintenance period, which can be much longer: for that whole period the Wallet Provider keeps the revocation status of the Wallet Instance available. If the Wallet Instance is compromised, the Wallet Provider revokes it. A PID Provider must check that status regularly for as long as its PID is valid, and revoke the PID once the Wallet Instance is revoked. Attestation Providers may do the same.
To protect privacy, a Wallet Unit presents its WIA only to PID Providers and Attestation Providers, never to Relying Parties. A Relying Party cannot check the Wallet Unit itself. It trusts the issuer to have checked the WIA, and by checking the revocation status of a PID it also knows the Wallet Unit behind it has not been revoked.
Business wallets work differently. The ARF assumes a personal device and leaves wallets for legal persons to a separate business wallet. The Commission's proposal for European Business Wallets (COM(2025) 838) carries the idea over under the name wallet unit attestation: the provider generates and signs one for each European Business Wallet unit, signed with a certificate issued under a certificate on the trusted list of Implementing Regulation (EU) 2024/2980. Such a unit is not just an app. It combines a front-end, a user interface of any platform or form factor, with a server-side back-end that must use at least one WSCA and WSCD to manage critical assets. The keys in the attestation must be protected by a WSCD, and a revoked attestation must have its status published.
OpenID4VCI describes its wallet attestation as designed especially for native app wallets, whose integrity the Wallet Provider typically checks with the mobile operating system, such as iOS DeviceCheck or Android Play Integrity. The proposal does not say how a server-side back-end proves its integrity. It leaves the technical specifications to implementing acts, which it says should build on the ARF where appropriate.
Does a Relying Party check the WIA?
No. Under the ARF, a Wallet Unit presents its Wallet Instance Attestation only to PID Providers and Attestation Providers during issuance, because they have a valid business reason to check the Wallet Instance and Relying Parties do not. A Relying Party trusts the issuer to have checked the WIA, and for a PID it relies on the revocation status of the PID to know the Wallet Unit has not been revoked.