OpenID4VCI Library (VCI Client)

Verifiable Credentials Issuance (VCI Client)

VCI Client library enables carrying out the credential request from the consumer application (mobile wallet or web) and downloading the VC.

Features:

• Request credentials from OID4VCI-compliant credential issuers
• Supports both the Verifiable Credential download flows defined in the OID4VCI specification:

  • Issuer Initiated Flow (Credential Offer Flow).
  • Wallet-initiated flow (Trusted Issuer Flow).
• Authorization server discovery for both download flows
• PKCE-compliant OAuth 2.0 Authorization Code flow (RFC 7636)

  • PKCE session is managed internally by the library
• Well-defined exception handling with VCI-XXX error codes (see more on this)
• Support for multiple Credential formats:

  • ldp_vc
  • mso_mdoc
  • vc+sd-jwt / dc+sd-jwt
• Presentation During Issuance (PDI) support for both download flows

⚠️ Consumer of this library is responsible for processing and rendering the credential after it is downloaded.

• Kotlin and Swift artifacts are available to integrate with the native mobile applications.

The section details the steps for integrating the Kotlin and Swift packages into the app.

Kotlin package for vci-client:

Repository

• inji-vci-client repo is here

Supported platforms

• Android (via aar)
• JVM (via jar)

Installation

Snapshot builds are available here.

Note: implementation "io.inji:inji-vci-client:0.7.0"

iOS: Swift package for vci-client:

Repository

• inji-vci-client-ios-swift repository

Installation

Add VCIClient to your Swift Package Manager dependencies:

.package(url: "https://github.com/inji/inji-vci-client-ios", from: "0.7.0")

APIs

The library provides the following APIs for credential issuance:

Use Case	Method Name	Description
Obtain Issuer Metadata	getIssuerMetadata()	Retrieve issuer metadata from well-known endpoint
Get Supported Credentials	getCredentialConfigurationsSupported()	Get supported credential configurations from issuer
Fetch Credential (Credential Offer)	fetchCredentialUsingCredentialOffer()	Request credential using credential offer (Pre-Auth/Auth flows)
Fetch Credential (Trusted Issuer)	fetchCredentialFromTrustedIssuer()	Request credential from a trusted issuer (Auth flow)

Note: For detailed API documentation including parameters, return types, and usage examples, refer to the Kotlin API Reference or Swift implementation documentation.

VCI-Client and Inji Wallet integration:

The diagram below shows how Inji Wallet utilises the vci-client library.