• Verifiable Credential
• Self Sovereign Identity
• Hyperledger Besu
• Ethereum public testnet
• private permissioned network
• smart contract
• blockchain
• layered trust management system

The Self Sovereign Identity (SSI) is a new paradigm for the management of the digital identities of users, which exploits decentralization to give back control of the identity information to the users. Despite the increased interoperability and control provided by the SSI, the current paradigm suffers from trust issues because the real identities of users are unknown to each other.
This thesis proposes a new trust management system specifically designed to support the paradigm of the SSI. More precisely, we propose a blockchain-based system that builds different levels of the Web of Trust by modelling both social and authority interactions between the entities that compose the SSI
standards: verifiers, issuers and holders of verifiable credentials. The evaluation results obtained by using a real dataset, applied on a private blockchain network built using Hyperledger Besu and on the Goerli public testnet, show that the proposed system is able to enhance the security of the SSI with a trust evaluation scheme supporting users' interactions also when considering completely unknown entities.