A multi-layer trust framework for Self Sovereign Identity on blockchain

The recent interest for decentralised systems and decentralisation of the control over users’ data brings a shift in the way identities and their information are managed. Self Sovereign Identity (SSI) has been proposed as the next generation paradigm for decentralised identity management. Research on SSI is getting more and more traction, focusing mainly on the management of users’ identifiers and on providing a standard way to express and verify credentials. Instead, this paper focuses on the understanding of the role of trust in SSI and it provides new insight into the trust relationships existing between the different SSI actors. Indeed, the analysis of such roles and the relationships existing between SSI actors reveals that the current paradigm suffers from trust issues between the verifier and the issuer of a verifiable credential.

In order to cope this problem, the paper proposes a new multi-layer framework that exploits trust relationships defined by the actors of the SSI standards (verifiers and issuers of verifiable credentials). An implementation of the framework through Solidity smart contracts has been proposed and deployed on both private and public blockchain networks in order to assess its capabilities. In addition, a dataset related to the spread of spam reviews has been exploited to test the benefits and performance of the proposed framework, demonstrating that it is able to improve the reliability of the SSI paradigm in real-world scenario.