Standards Alignment

This document describes how zk-id maps to existing identity verification standards, particularly ISO 18013-5 (mobile Driving License) and ISO 18013-7 (online age verification).

ISO 18013-5 (mDL)

ISO 18013-5 defines the data model and security mechanisms for mobile driving licenses (mDL). While zk-id is not an mDL implementation, it provides functional overlap for age and nationality verification.

Data Element Mapping

zk-id Attribute	mDL Element	Identifier	Fidelity	Notes
`birthYear`	`birth_date`	`org.iso.18013.5.1.birth_date`	Partial	zk-id stores year only; mDL uses full date
`nationality`	`nationality`	`org.iso.18013.5.1.nationality`	Partial	zk-id uses ISO 3166-1 numeric; mDL uses alpha-2
`credential.id`	`document_number`	`org.iso.18013.5.1.document_number`	Partial	Different identifier formats
`issuer`	`issuing_authority`	`org.iso.18013.5.1.issuing_authority`	Partial	String identifier vs. X.509 subject
`issuedAt`	`issue_date`	`org.iso.18013.5.1.issue_date`	Exact	Both use ISO 8601

Country Code Conversion

zk-id uses ISO 3166-1 numeric codes (e.g., 840 for USA); mDL uses alpha-2 codes (e.g., “US”). The @zk-id/issuer package provides bidirectional conversion tables:

import { ISO_3166_NUMERIC_TO_ALPHA2, ISO_3166_ALPHA2_TO_NUMERIC } from '@zk-id/issuer';

ISO_3166_NUMERIC_TO_ALPHA2[840]; // "US"
ISO_3166_ALPHA2_TO_NUMERIC['GB']; // 826

mDL Element Export

Convert a zk-id credential to mDL-aligned data elements:

import { toMdlElements } from '@zk-id/issuer';

const elements = toMdlElements(signedCredential, 'US');
// Returns: [
//   { identifier: "org.iso.18013.5.1.birth_date", value: "1990-01-01" },
//   { identifier: "org.iso.18013.5.1.nationality", value: "US" },
//   { identifier: "org.iso.18013.5.1.issuing_authority", value: "Gov-ID" },
//   ...
// ]

ISO 18013-7 (Online Age Verification)

ISO 18013-7 defines the online presentation protocol for mDL, including age_over_NN attestation. This maps directly to zk-id’s age proof system.

Age-Over Attestation

When a zk-id age proof verifies successfully, the result can be expressed as an ISO 18013-7 age_over_NN attestation:

import { createAgeOverAttestation } from '@zk-id/issuer';

// After successful verification of minAge=18:
const attestation = createAgeOverAttestation(18);
// {
//   ageThreshold: 18,
//   elementId: "org.iso.18013.5.1.age_over_18",
//   value: true
// }

Privacy Comparison

Feature	zk-id	ISO 18013-7
Proves age >= threshold	Yes (ZK proof)	Yes (age_over_NN)
Reveals exact birth date	No	No (for age_over)
Reveals issuer identity	Yes (in signed credential)	Yes (in mDL)
Proof mechanism	Groth16 ZK-SNARK	Selective disclosure via MDOC
Offline support	No (requires verifier server)	Yes (proximity via NFC/BLE)
Replay protection	Nonce + timestamp binding	Session transcript hash

Architectural Differences

Concept	zk-id	ISO 18013-5/7
Credential binding	Poseidon commitment	MSO (Mobile Security Object)
Signature scheme	Ed25519	ECDSA or EdDSA via COSE
Issuer trust	Registry with key rotation	X.509 certificate chains (VICAL)
Revocation	Merkle inclusion proof (valid-set)	Status lists (future extension)
Proof system	Groth16 on BN128	MDOC selective disclosure
Transport	HTTPS + JSON	MDOC + CBOR

Multi-Claim Proofs

zk-id supports proving multiple claims in a single verification session via the multi-claim API:

import { createMultiClaimRequest, expandMultiClaimRequest } from '@zk-id/core';

const request = createMultiClaimRequest(
  [
    { label: 'drinking-age', claimType: 'age', minAge: 21 },
    { label: 'citizenship', claimType: 'nationality', targetNationality: 840 },
  ],
  nonce,
);

// Expand to individual proof requests (same nonce binding)
const proofRequests = expandMultiClaimRequest(request);

This parallels ISO 18013-7’s capability to request multiple data elements in a single session, though the underlying mechanisms differ (ZK proofs vs. selective disclosure).

Full Mapping Table

The complete programmatic mapping is available via STANDARDS_MAPPINGS in @zk-id/issuer:

import { STANDARDS_MAPPINGS } from '@zk-id/issuer';

for (const m of STANDARDS_MAPPINGS) {
  console.log(`${m.zkIdConcept} → ${m.standard} ${m.standardConcept} (${m.fidelity})`);
}

Roadmap

Future standards alignment work:

W3C Verifiable Credentials Data Model 2.0 full compliance
ISO 18013-5 CBOR/COSE encoding option
IETF SD-JWT interoperability

Last updated: 2026-02-09