Credential issuer

A credential issuer is a protected REST API capable of issuing Verifiable Credentials.

The Digital Credentials Protocols (DPC) working group of the OPENID standard has authored a technical specification for developing Credential Issuers. For more information, please refer to the official documentation.

In this article, we will develop a REST API for a University capable of issuing University degrees to its students. The REST API adheres to the following technical specifications:

• Verifiable credentials are returned in the ldp_vc format.
• The did:key algorithm is utilized to transform the credential into a verifiable credential.

1. Configure a scope

If a university_degree scope is configured, then skip this step.

Utilize the administration UI to configure a new scope :

1. Open the IdentityServer website at https://localhost:5002/master/clients.
2. On the Scopes screen, click on the Add scope button.
3. Select API value and click on next.
4. Fill-in the form like this and click on the Save button to confirm the creation.

Parameter	Value
Name	university_degree
Description	University degree

2. Configure an application

Utilize the administration UI to configure a new OpenID client :

1. Open the IdentityServer website at https://localhost:5002/master/clients.
2. In the Clients screen, click on Add client button.
3. Select Credential Issuer.
4. Fill-in the form like this and click on the Save button to confirm the creation.

Parameter	Value
Identifier	CredentialIssuer
Secret	password
Name	Credential Issuer
Redirect URLS	https://localhost:5005/*

5. Click on the new client, then select the Client scopes tab click on the Add client scope button. Choose the university_degree scope and click on the Save button.

3. Create credential issuer

Create and configure the credential issuer API.

1. Open a command prompt and execute the following commands to create the directory structure for the solution :

mkdir CredentialIssuer
cd CredentialIssuer
mkdir src
dotnet new sln -n CredentialIssuer

2. Use the SimpleIderver template to create the credential issuer project :

cd src
dotnet new credissuer -n CredentialIssuer

3. Add the CredentialIssuer project into the solution :

cd ..
dotnet sln add ./src/CredentialIssuer/CredentialIssuer.csproj

By default, the CredentialIssuer project is configured to issue Verifiable Credentials, such as the UniversityDegree.

The project configuration is located in the CredentialIssuerConfiguration.cs file, which contains the following properties:

CredentialConfigurations: Definitions of credentials and the mapping rules with the user's claims. CredentialClaims: Claims of the user.

In a command prompt, navigate to the src\CredentialIssuer directory and launch the application.

dotnet run --urls=https://*:5005

Please browse the following URL: https://localhost:5005/credentials. The User-Agent will be automatically redirected to the OpenID server. Submit the following credentials and confirm the consent. You will then be redirected to a screen where your claims will be displayed.

Credential	Value
Login	administrator
Password	password

Finally, click on the Share button next to the University Credential. A QR will be displayed in a popup window :

3. Enroll verifiable credentials

If the mobile application is not yet installed, follow this tutorial.

Scan the QR code displayed by the credential issuer. If the enrollment is successful, a success message will be displayed. The verifiable credential is now visible in the Wallet tab.