Frequently asked questions

Answers to common questions about credential holding with MATTR. For the concepts behind these answers, see the holding overview.

Frequently asked questions

Can I add credential holding to my existing app without rebuilding it?

Yes. The MATTR Pi Holder SDK is designed to be added to existing mobile applications. You integrate it as a native dependency (CocoaPods/SPM for iOS, Maven/Gradle for Android, npm for React Native) and call SDK methods from your existing codebase.

What's the difference between MATTR Pi Holder SDK and MATTR GO Hold?

The MATTR Pi Holder SDK is a library you embed in your own app, so you control the full user experience. MATTR GO Hold is a standalone wallet application ready for end users. Choose the SDK for custom integration. Choose GO Hold for rapid deployment or pilots.

Does the SDK work offline?

Yes, for proximity presentation. The SDK uses BLE for in-person credential exchange and can verify credentials against locally cached trusted issuer certificates and status lists. Credential claiming and remote presentation require network connectivity.

Which credential formats are supported?

The MATTR Pi Holder SDK supports mDocs (aligned with ISO/IEC 18013-5) for both claiming and presentation. This includes mobile driver's licenses (mDLs) and other mDoc-based credentials.

How are credentials stored securely?

The SDK uses platform-native secure storage: iOS Keychain and Android Keystore. Credential keys are hardware-backed where available and bound to the device. Credentials cannot be extracted or cloned to another device.

Can my app claim credentials from any issuer?

Your app can claim credentials from any issuer using the OID4VCI standard. For verification of issuer trust, configure your trusted issuer certificate list to include the IACA certificates of issuers you accept.

How do I handle credential revocation in my app?

The SDK automatically checks status lists based on the issuer's ttl and exp configuration. Your app should handle the case where a previously valid credential's status changes. Surface this to the user and, if appropriate, prompt them to obtain a replacement.

Can users present credentials to verifiers not using MATTR?

Yes. Because the SDK implements ISO/IEC 18013-5 (proximity) and ISO/IEC 18013-7 + OID4VP (remote), your app can present credentials to any standards-compliant verifier regardless of their platform provider.

What happens if the user switches devices?

Credentials are bound to the device's secure storage and cannot be transferred. Users will need to re-claim their credentials on a new device through the original issuer's offer flow.

How long does SDK integration typically take?

Basic credential claiming can be integrated in days. A full implementation covering claiming, proximity presentation, and remote presentation with polished UX typically takes 2–4 weeks for an experienced mobile team. The quickstart guide gets you to a first working integration quickly.