Part 4 — A Real System: CredGuard

The previous parts covered ideas and standards in the abstract. Part 4 brings them together in a concrete, working system.

CredGuard is a full SSI demo: a Spring Boot backend implementing OID4VCI and OID4VP, a Next.js frontend with three portal UIs, and a mobile wallet built on Credo-TS. It demonstrates three complete end-to-end flows:

1. A government officer issues a digital passport to a traveller's wallet
2. An embassy officer requests proof of passport, verifies it, and issues a visa — delivered automatically to the same wallet
3. An airport kiosk requests both passport and visa simultaneously, verifies both, and automatically issues a boarding pass

Each of the four chapters in this part walks through one of these flows in detail — explaining every HTTP call, every credential exchange, and every protocol decision.

Coming soon.