Build a product wallet

Make your wallet speak VCALM: pick up and present provenance credentials over an exchange.

You'll do exactly 3 things

1. Dereference an interaction URL to discover protocols.
2. POST to the exchange URL to start.
3. Loop: read verifiablePresentationRequest / verifiablePresentation, POST back, until done.

1. Discover protocols

A scanned tag or QR code encodes an interaction URL with iuv=1. GET it:

GET /interactions/bag-456?iuv=1
Host: tag.brand.example
Accept: application/json

The response lists supported protocols; pick vcapi for VCALM:

{
  "protocols": {
    "vcapi": "https://vcapi.brand.example/exchanges/bag-456"
  }
}

2. Start the exchange

POST an empty body to the vcapi URL:

POST /exchanges/bag-456
Host: vcapi.brand.example
Content-Type: application/json

{}

3. Run the loop

When the server returns a verifiablePresentationRequest, find the matching provenance credential, build a signed Verifiable Presentation, and POST it back to the same exchange URL. When the server returns a verifiablePresentation, store the delivered credential. The exchange is done when the server stops asking.

That's it

A conformant product wallet is this loop. Nothing more.

Go deeper

• VCALM: verifiable presentation request
• VCALM specification

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