Toward Interoperable Self-Sovereign Identities

Self-sovereign identity is a digital identity paradigm that allows users and organizations to manage digital identity in a decentralized fashion without any central authority controlling the process of issuing identities and verifying assertions. Following this paradigm, implementations have emerged in recent years, with some having different underlying technologies. These several technological differences often create interoperability problems between software that interact with each other from different implementations. Although a common problem, there is no common understanding of interoperability in the context of self-sovereign identities. In this tutorial paper, we propose a definition of interoperability of self-sovereign identities to enable a shared understanding. Moreover, due to the decentralized nature, interoperability of self-sovereign identities depends on multiple components, such as ones responsible for establishing a cryptographic trust or enabling secure communication between entities without centralized authorities. To understand those components and their dependencies, we also present a reference model that maps the required components and considerations that build up a self-sovereign identity implementation. The reference model enables addressing how to achieve interoperability between different implementations.