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Glossary

This glossary defines acronyms and terminology used across the ewQwe Age Verification project and the broader EU digital identity ecosystem.

A

ARF — Architecture and Reference Framework The EU Commission’s technical blueprint for the European Digital Identity Wallet ecosystem. Defines the architecture, roles, and interoperability requirements for all EUDI components.

Attestation A digitally-signed document issued by a trusted authority that asserts facts about a subject (e.g. “this person is over 18”). The general term used in the EU ARF for any credential or verifiable document, whether mDL, PID, or any other type.

AVI — Age Verification App Instance Term used in the EU Age Verification Profile for the wallet-side component that stores and presents Proof of Age attestations. Corresponds to the wallet/ component in this project.

B

Binding Proof → see Holder Binding Proof

C

CBOR — Concise Binary Object Representation (RFC 7049 / RFC 8949) A binary data serialization format, similar to JSON but more compact. Used extensively in mDoc/mDL credentials. All mso_mdoc structures are CBOR-encoded.

CDDL — Concise Data Definition Language (RFC 8610) A schema language for describing CBOR data structures. Used in ISO 18013-5 to formally define mDoc structures.

CIR — Commission Implementing Regulation EU regulatory acts that specify technical details of the EUDI Wallet framework. CIR 2024/2977 defines the PID attribute set.

client_id In OpenID4VP, the identifier of the Relying Party (Verifier). The format depends on the client_id_scheme:

  • redirect_uri:https://rp.example.com/cb — RP identified by its redirect URI (AnnexA profile)
  • x509_san_dns:rp.example.com — RP identified by a DNS SAN in its X.509 certificate (HAIP profile)
  • x509_hash:<base64url_sha256> — RP identified by the SHA‑256 hash of its leaf X.509 certificate (HAIP profile, recommended over x509_san_dns)

cnf — Confirmation Claim (RFC 7800) A JWT claim that contains the holder’s public key (usually as a jwk). Used in SD-JWT VCs to bind the credential to a specific cryptographic key, enabling holder binding.

COSE — CBOR Object Signing and Encryption (RFC 8152 / RFC 9052) The CBOR equivalent of JOSE (JSON Object Signing and Encryption). Defines:

  • COSE_Sign1 — single-signer signatures
  • COSE_Mac0 — message authentication codes
  • COSE_Encrypt0 / COSE_Encrypt — encryption structures

COSE_Sign1 A COSE structure for a signed object with a single signer. Used for MSO (issuer auth) and device signatures in mso_mdoc. Structure: [protected_header, unprotected_header, payload, signature].

D

DC API — Digital Credentials API A W3C browser API (navigator.credentials.get()) that enables web pages to request verifiable credentials from wallets. Replaces the earlier WebAuthn-based flow for identity credentials.

DCQL — Digital Credentials Query Language A JSON-based query language used in OpenID4VP dcql_query parameter to specify which credential types and claims are requested. More expressive than Presentation Exchange (PE).

DeviceAuthentication An mDL CBOR structure that the device (holder) signs to prove session binding. Contains: ["DeviceAuthentication", SessionTranscript, DocType, DeviceNameSpacesBytes]. The signed bytes are DeviceAuthenticationBytes = Tag(24, bstr(cbor(DeviceAuthentication))).

DeviceSigned The part of an mDoc Document that contains the device-generated signature (DeviceAuth) and any device-disclosed namespaces. Proves the holder controls the credential’s device key.

Disclosure (SD-JWT) A base64url-encoded JSON array [salt, claim_name, claim_value] that reveals a single selectively-disclosed claim. The holder includes chosen Disclosures in a presentation.

docType The CBOR text string identifier for an mDoc credential type. Examples:

  • org.iso.18013.5.1.mDL — Mobile Driver’s Licence
  • eu.europa.ec.eudi.pid.1 — EU Person Identification Data
  • eu.europa.ec.eudi.ageproof.1 — EU Age Verification (AVI profile)

E

EUDI Wallet — European Union Digital Identity Wallet The EU-standardised digital wallet app (Android/iOS) for holding and presenting European Digital Identity documents. Governed by the EU ARF.

EC — Elliptic Curve Cryptographic scheme used for compact key sizes and signatures. Common curves in this project:

  • P-256 (secp256r1): used for ES256 signatures, JWK thumbprints
  • P-384 (secp384r1): used for ES384 signatures

H

HAIP — High Assurance Interoperability Profile An OpenID4VP profile requiring JARM (response_mode=direct_post.jwt) and X.509-based RP authentication (client_id_scheme=x509_hash). Provides higher security guarantees than the basic profile.

Holder The entity (person, organisation) who possesses a credential and presents it to verifiers. In this project, corresponds to the wallet / AVI.

Holder Binding Proof Proof that the holder of a credential controls the private key bound to it. This prevents credential theft — a stolen credential is useless without the binding key.

  • In mso_mdoc: the DeviceSigned block containing a COSE_Sign1 over DeviceAuthenticationBytes signed with the device private key
  • In SD-JWT VC: the Key Binding JWT (KB-JWT) signed with the key in the cnf.jwk claim

See OpenID4VP §5.3.

I

ISO 18013-5 The ISO standard defining the Mobile Driver’s Licence (mDL) data model and presentation protocol. Basis for the mso_mdoc credential format and the COSE-based signing scheme used across EU digital credentials.

Issuer A trusted authority that issues credentials (attests facts about a subject). Signs the MSO (mDL) or the JWT (SD-JWT VC).

IssuerSigned The part of an mDoc Document containing the issuer-authenticated claims and the MSO (COSE_Sign1). Enables selective disclosure — only the chosen IssuerSignedItem entries are revealed.

IssuerSignedItem A single disclosed claim in an mso_mdoc document. Contains: digestID, random (salt), elementIdentifier (claim name), elementValue (claim value). Encoded as Tag(24, bstr(cbor(IssuerSignedItem))).

J

JARM — JWT Secured Authorization Response Mode An extension of OAuth 2.0 that wraps authorization responses in a JWT. In OpenID4VP, response_mode=direct_post.jwt uses JWE/JWS to encrypt/sign the VP Token response from wallet to RP. Required by the HAIP profile.

JWE — JSON Web Encryption (RFC 7516) A standard for encrypting data as a JSON structure. Used in JARM to encrypt the VP Token when response_mode=direct_post.jwt.

JWK — JSON Web Key (RFC 7517) A JSON representation of a cryptographic key (EC or RSA). The verifier’s JWK is used to encrypt JARM responses; its thumbprint is included in the SessionTranscript for HAIP flows.

JWK Thumbprint (RFC 7638) A SHA-256 hash of the canonical JSON representation of a JWK. Used in the OID4VPHandoverInfo to bind the session transcript to the verifier’s encryption key.

JWS — JSON Web Signature (RFC 7515) A standard for signing data as a JSON structure. The basis for standard JWTs and SD-JWT VC issuer signatures.

JWT — JSON Web Token (RFC 7519) A compact, URL-safe representation of claims signed (and optionally encrypted) as JSON.

K

KB-JWT — Key Binding JWT The trailing JWT in an SD-JWT presentation that proves the holder controls the key in cnf.jwk. Contains aud, nonce, iat, and sd_hash. Required for holder binding in SD-JWT VC presentations.

M

mDL — Mobile Driver’s Licence A digital driving licence defined by ISO/IEC 18013-5. Uses the mso_mdoc credential format with docType org.iso.18013.5.1.mDL.

mDoc / mso_mdoc Short for “Mobile Document” / “Mobile Security Object + mDoc”. The credential format defined in ISO 18013-5 using CBOR encoding and COSE signing. Used for mDL, EU PID, EU Age Verification, and other digital documents.

MSO — Mobile Security Object The signed CBOR data structure embedded in an mDoc’s issuerAuth COSE_Sign1. Contains SHA-256 digests of each claim (rather than the values themselves), enabling selective disclosure while maintaining issuer authenticity.

N

Namespace In mDL/mDoc, claims are grouped into namespaces (CBOR text strings). Examples:

  • org.iso.18013.5.1 — Core mDL attributes (given_name, birth_date, etc.)
  • org.iso.18013.5.1.aamva — North American additions
  • eu.europa.ec.eudi.pid.1 — EU PID attributes

nonce A random value included in an Authorization Request to prevent replay attacks. Bound into the SessionTranscript (mDL) or KB-JWT (SD-JWT VC) of the presentation.

O

OID4VP / OpenID4VP — OpenID for Verifiable Presentations The protocol used to request and receive Verifiable Presentations from a wallet. Builds on OAuth 2.0 authorization flows. Supports both mso_mdoc and SD-JWT VC credential formats. Key specs versions: 1.0 (current stable).

OID4VCI / OpenID4VCI — OpenID for Verifiable Credential Issuance The companion protocol to OID4VP for issuing credentials into wallets.

P

PE — Presentation Exchange An older query language for specifying credential requirements in OID4VP, defined by the Decentralized Identity Foundation (DIF). Being superseded by DCQL in newer profiles.

PID — Person Identification Data The EU digital identity credential containing core identity attributes (name, birth date, nationality, etc.). Specified in CIR 2024/2977. Available in both mso_mdoc and SD-JWT VC formats.

Presentation / VP A holder-constructed object that packages one or more credentials (or selective disclosures from them) together with holder binding proof, for transmission to a verifier. In OpenID4VP the main artifact is called the VP Token.

Proof of Age (PoA) / Age Verification Attestation A credential or derived presentation that proves an age threshold (e.g. “over 18”) without revealing exact birth date. Core use case of this project.

R

RP — Relying Party The service or application that requests and verifies credentials. Also called Verifier. In this project, corresponds to the webapp/ component.

response_mode OpenID4VP parameter controlling how the wallet returns the VP Token:

  • fragment — appended to redirect URI as URL fragment (same-device, cross-origin)
  • direct_post — wallet POSTs to response_uri (cross-device or CORS-friendly)
  • direct_post.jwt — wallet POSTs a JWE/JWS-wrapped VP Token (HAIP/JARM)
  • dc_api — delivered via browser DC API (no redirect needed)
  • dc_api.jwt — DC API with JARM wrapping

response_uri The URL to which the wallet POSTs the VP Token in direct_post and direct_post.jwt modes.

S

Salted Hashing The mechanism used for selective disclosure in both mDL and SD-JWT. Each claim is combined with a random salt before hashing. This prevents a verifier from guessing undisclosed claim values by brute-forcing the hash.

SAN — Subject Alternative Name An X.509 certificate extension field listing alternative identities for the certificate subject (DNS names, IP addresses, email). Used in x509_san_dns client_id scheme to identify RPs.

SD-JWT VC — Selective Disclosure JWT for Verifiable Credentials A credential format combining standard JWTs with selective disclosure via SHA-256 commitments. Defined in IETF SD-JWT VC.

SessionTranscript An mDL CBOR structure that ties a device signature to a specific presentation session. For OID4VP flows it contains the OID4VPHandover, which commits to the client_id, nonce, response_uri, and (for HAIP) the verifier’s JWK thumbprint.

_sd The JSON array in an SD-JWT VC issuer JWT that holds base64url-encoded SHA-256 digests of the Disclosures. The holder reveals values by including the matching Disclosures in the presentation.

_sd_alg The hash algorithm used for Disclosure digests in SD-JWT VCs. Currently always sha-256.

T

Tag(24) — #6.24(bstr) A CBOR semantic tag applied to a byte string to indicate that its content is CBOR-encoded. Extensively used in mDL:

  • IssuerSignedItemBytes = #6.24(bstr .cbor IssuerSignedItem)
  • DeviceAuthenticationBytes = #6.24(bstr .cbor DeviceAuthentication)
  • DeviceNameSpacesBytes = #6.24(bstr .cbor DeviceNameSpaces)

The full Tag(24, bstr(...)) encoding must be hashed/signed, not just the inner bytes.

V

VC / Verifiable Credential A tamper-evident credential whose authorship can be cryptographically verified. The W3C Verifiable Credentials Data Model provides a general framework; mso_mdoc and SD-JWT VC are two concrete serialisations.

Verifiable Presentation / VP A holder-generated package wrapping one or more Verifiable Credentials and a binding proof. Transmitted to a verifier (RP) in response to a presentation request.

Verifier → see RP

VP Token The OpenID4VP parameter name for the value carrying the Verifiable Presentation. For mso_mdoc it is the base64url-encoded DeviceResponse; for SD-JWT VC it is the SD-JWT string.

vct — Verifiable Credential Type A URI in SD-JWT VC that identifies the type/schema of the credential. E.g. https://credentials.example.com/identity_credential.

W

W3C DC API → see DC API

Wallet The software (mobile app or browser extension) that stores, manages, and presents digital credentials on behalf of the holder. In this project: the wallet-extension/ browser wallet or the EUDI Android Wallet.

X

x5chain (COSE header label 33) An unprotected COSE header containing a DER-encoded X.509 certificate chain. Used in mDL issuerAuth to carry the issuer certificate for chain verification.

x5c (JOSE header) The JSON/JWT equivalent of x5chain. An array of base64-encoded DER X.509 certificates. Used in JAR (JWT Authorization Request) to carry the RP’s certificate for x509_hash / x509_san_dns verification.

See the centralized reference list for all authoritative sources (RFCs, ISO standards, specifications).