Credential Aggregation

Full Title or Meme

In the real-world a person is likely to need to produce more than one certificate from the wallet to get access to high value locations. This use case looks at how that effort might be addressed when Credentials are held in digital format.

Context

• To reify this abstract concept we will use a Smartphone to digitize John's common practice of actually using his gym membership. The following credentials are displayed to the desk attendant today.

1. Gym membership card - typically will include an expiration date.
2. Driver's license - to provide a biometric image for verification.
3. Smart Health Card - to prove vaccination or current testing.

Principles

• The user will provide no data that is not required for the purpose desired for this access.

Taxonomy

• Credential is a collection of user attributes attested by the issuer.*
• Attribute or Identifier are terms used in Identifier Management for Authentication information.
• Data element can represent an attribute, identifier or details of the digital world.
• Claim as defined in NIST or SAML publication is just a statement the user makes about themselves. Sometimes this is confused with attribute.
• Verified can applied to Credentials, Presentations or Attributes.
• Digital Presentation is a data minimized collection of user attributes from one or more credentials.
• User Experience or presentation of options to the user for their consent.

Problems

• In the real world only a few sites ask to make copies of your credentials and collect more data than they need in the process.
• In the digital world collecting the full credential exposes the user to signification loss of Privacy.
• Many issuers of credentials are very specific about which wallet can be used to store their credential with adequate security.
• The Verifiable Credential spec comes with a very specific presentation format which is both exclusive to its use and broad the the range that be be request and delivered.
• Other credentials, like the Smart Health Card (shc:) are completely independent of the wallet and are accepted by existing Smartphones. In some cases the shc is stored in a health app rather than in the wallet.

Solutions

• As a general rule the user's entire credential data contents should not be passed to any Relying Party whether in-person or on-line.
• Presentation apps are likely to exist based on the needs of the Relying Party and will need to be able to acquire data from all sorts of credentials. In some cases these will be delivered to the user with the Smartphone.
• Since many of the wallets are not configurable to talk to other apps on the Smartphone, it is expected that most presentation apps will be provided as Progressive Web Apps. In many cases these will be from the Relying Party or a Federation of Relying Parties.