Blockchain-Based Self-Sovereign Identity: Survey, Requirements, Use-Cases, and Comparative Study

Identity is at the heart of digital transformation. Successful digital transformation requires confidence in and protection of digital identities. On the Internet, however, there is no unique and standard identity layer. Consequently, a variety of digital identities have emerged over years, leading to privacy risks, security vulnerabilities, risks for identity owners, and liability for identity issuers and those relying on digital identities to grant access to goods and services. Self-Sovereign Identity (SSI) and similar forms of identity management on the blockchain distributed ledger are novel technologies that recognize the need to keep user identity privately stored in user-owned devices, securely verified by identity issuers, and only revealed to verifiers as needed. There is limited academic literature defining the prerequisite SSI functional and non-functional requirements and comparing SSI technologies. Often those SSI technologies reviewed in the literature lack behind current advances. We present the first work that compiles a comprehensive list of functional and non-functional requirements of SSI and compares an extensive number of existing SSI/blockchain-based identity management solutions with respect to these requirements. Our work sheds light on the state-of-the-art SSI development and paves the way for future, more informed analysis and development of novel identity management and SSI solutions.