# Verifiable Credentials (VCs)

Verifiable Credentials are a W3C standard for expressing credentials in a way that is cryptographically secure, privacy-respecting, and machine-verifiable. They enable trusted digital claims about subjects.

### Verifiable Credential Data Model <a href="#credential-data-model" id="credential-data-model"></a>

LearnCard implements the W3C Verifiable Credentials Data Model, with support for both VC 1.0 and VC 2.0 formats. The core data types are defined using Zod validators.

#### Credential Structure <a href="#credential-structure" id="credential-structure"></a>

{% @mermaid/diagram content="graph
subgraph "Verifiable Credential"
VC\["Verifiable Credential"]
VC --> Context\["@context"]
VC --> ID\["id"]
VC --> Type\["type"]
VC --> Issuer\["issuer"]
VC --> IssuanceDate\["issuanceDate"]
VC --> Subject\["credentialSubject"]
VC --> Proof\["proof"]

```
    Subject --> SubjectID["id (DID of subject)"]
    Subject --> Claims["Claims (achievements, skills, etc.)"]

    Proof --> ProofType["type (e.g., Ed25519Signature2020)"]
    Proof --> Created["created"]
    Proof --> VM["verificationMethod"]
    Proof --> Purpose["proofPurpose"]
    Proof --> JWS["jws (signature)"]
end" %}
```

| Component           | Description                              | Required |
| ------------------- | ---------------------------------------- | -------- |
| `@context`          | JSON-LD contexts defining the vocabulary | Yes      |
| `id`                | Unique identifier for the credential     | No       |
| `type`              | Array of credential types                | Yes      |
| `issuer`            | Entity that issued the credential        | Yes      |
| `credentialSubject` | Entity the credential is about           | Yes      |
| `proof`             | Cryptographic proof of authenticity      | Yes      |

Version differences:

* VC 1.0 uses `issuanceDate` and `expirationDate`
* VC 2.0 uses `validFrom` and `validUntil`

{% @github-files/github-code-block url="<https://github.com/learningeconomy/LearnCard/blob/942bb5f7/packages/learn-card-types/src/vc.ts#L129-L177>" %}

<br>

## Verifiable Presentations (VPs) <a href="#verifiable-presentations-vps" id="verifiable-presentations-vps"></a>

Verifiable Presentations allow holders to bundle and selectively disclose credentials:

{% @mermaid/diagram content="graph
subgraph "Verifiable Presentation"
VP\["Verifiable Presentation"]
VP --> VPContext\["@context"]
VP --> VPID\["id"]
VP --> VPType\["type"]
VP --> Holder\["holder"]
VP --> VCs\["verifiableCredential\[]"]
VP --> VPProof\["proof"]

```
    VCs --> VC1["Credential 1"]
    VCs --> VC2["Credential 2"]

    VPProof --> VPProofType["type"]
    VPProof --> VPCreated["created"]
    VPProof --> VPVM["verificationMethod"]
    VPProof --> VPPurpose["proofPurpose"]
    VPProof --> Challenge["challenge (optional)"]
    VPProof --> Domain["domain (optional)"]
    VPProof --> VPJWS["jws (signature)"]
end" %}
```