Disposable Yet Official Identities (DYOI) for Privacy-Preserving System Design - The case of COVID-19 digital document verification and credential-based access control in ad hoc outdoor and indoor settings (and beyond)

In this paper we report on the design of a service system to endow next-generation COVID-19 mobile applications with the capacity: a) to instantly manage and verify a wide range of possible COVID-19 digital documents (circulation attestations, work or travel permits based on approved COVID-19 tests, vaccination certificates, etc.) and, b) to provide credential-based access control, especially in cases where the Verifier is not a web entity but a human agent with a smartphone, or an IoT device -- mainly in ad hoc outdoor and indoor settings. The system has been designed as a response to the specific needs of a health emergency situation, but it may have a broader application in different cased and areas of control (such as airport and train stations checking points and board controls), where the verification process must exclude the possibility of a physical interaction between the controller and the subject of control, by maintaining a “safe distance” between them and while preserving a certain privacy for the subject of control. Our approach levers the potential of Disposable Identities, Self-Sovereign Identities technologies and Verifiable Credentials (VCs) to enable digital document verification and credential-based access control in ad hoc outdoor and indoor settings (and beyond). Towards this, we specifically introduce the concept of “Derivative” (i.e., transcoded/contextual) Verifiable Credentials. A Derivative VC is a derived bond contract guaranteeing the validity and ownership over the underlying contracts (VCs) whose: a) usability is restricted in a very specific context (that of the “local” and time-limited interaction between a Subject and a Service Provider) and, b) linking table points only to a specific “Pairwise DID”.