  Identity management systems (IDMSs) are widely used to provision user
identities while managing authentication, authorization, and data sharing
within organizations and on the web. Traditional identity systems typically
suffer from single points of failure, lack of interoperability, and privacy
issues, such as enabling mass data collection and user tracking. Blockchain
technology has the potential to alleviate these concerns: it can support the
ability for users to control the custody of their own identifiers and
credentials, enabling novel data ownership and governance models with built-in
control and consent mechanisms. Hence, blockchain-based IDMSs, which could
benefit both users and businesses, are beginning to proliferate. This work
categorizes these systems into a taxonomy based on differences in blockchain
architectures, governance models, and other salient features. Context is
provided for the taxonomy through the description of related terms, emerging
standards, and use cases while highlighting relevant security and privacy
considerations.
