Overview

Verifiable credentials (VCs) are digital credentials which follow the relevant World Wide Web Consortium open standards. They can represent information found in physical credentials, such as a passport or license, as well as new things that have no physical equivalent, such as ownership of a bank account. They have numerous advantages over physical credentials, most notably that they're digitally signed, which makes them tamper-resistant and instantaneously verifiable.

Verifiable credentials can be issued by anyone, about anything, and can be presented to and verified by everyone. The entity that generates the credential is called the Issuer. The credential is then given to the Holder who stores it for later use. The Holder can then prove something about themselves by presenting their credentials to a Verifier.

Trust model

The holder of a verifiable credential operates in a triangle of trust, mediating between issuer and verifier.

Any role in the triangle can be played by a person, an institution, or a machine.

Note that because verifiable credentials can be created by anyone, the verifier decides if they trust the issuer.

Decentralization

The VC model places the holder of a credential at the center of the identity ecosystem, giving individuals control of their identity attributes. The W3C VC model parallels physical credentials: the user holds cards and can present them to anyone at any time without informing or requiring the permission of the card issuer. Such a model is decentralized and gives much more autonomy and privacy to the participants.

This contrasts with the federated identity management (FIM) model, as adopted by SAML and OpenID Connect, which place the identity provider (IdP) in the central role as the dispenser of identity attributes and the determiner of which Service Providers (SPs) it will give them to. In the federated model, the IdP knows every SP that the user visits.

Verifiable Credentials Data Model 1.0

The data model for verifiable credentials is a World Wide Web Consortium (W3C) Recommendation, "Verifiable Credentials Data Model 1.0 - Expressing verifiable information on the Web", published 19 November 2019.

Aliases

The VC context, defined using the @context JSON property, is a JSON-LD construct that allows user friendly terms to be used for JSON properties. According to the VC data model, the value of many properties must be a URI. Whilst these are globally unambiguous, (important for a global data model), they are not user-friendly. Consequently, the @context property allows short-form, user-friendly aliases to be defined for each URI. This makes it much easier, and more user-friendly, to specify VCs. An example is given below.