## 3 Literature Review
### Blockchain-Based IDMSs
The researchers used an MVC (Model-View-Controller) structure for this purpose. The implemented framework improved user experience by creating a user login to many bank accounts without the need to remember all their accounts and passwords. The prototype applied the concept of self-sovereign identity in the open banking field and provided an efficient authentication framework. In [28], the authors tried to solve the problem of traffic disruption caused by malicious vehicles through incorrect information propagation. As a way to maintain privacy, they suggested using a blockchain-based authentication scheme and asymmetric key encryption to secure vehicle communication. Additionally, elliptic curve cryptography was used to increase transactions pseudonymity. According to the study of [34], it has been found that when cooperating with unauthorized vehicles, it is possible to steal information, compromise privacy, and exploit a variety of threats in terms of security. The authors proposed a blockchain-based Internet of Vehicles (IoV) protocol that was developed on the Ethereum platform, to improve the privacy of vehicle data and relationships with the help of blockchain technology. However, too much IoV information stored in the blockchain will affect the system's scalability. [35] In addition, the paper discussed the increased difficulty of managing certificates for vehicular communications, along with the cost of anonymizing vehicle identities. This study proposes a blockchain-based pseudonym management solution which has the ability to reuse existing pseudonyms in order to simplify pseudonym management. Additionally, in [30], the authors attempted to enhance vehicle privacy and trust relationships. As a result of the use of blockchain technology by these authors, they proposed a blockchain-based anonymous reputation system (BARS), which is based on a reputation evaluation algorithm. A proof-of-concept IoT identity management system for a business case scenario was implemented by the authors in [12], to ensure the integrity of the data provenance records in the organization-networked IOT resources using blockchain and smart contracts. Solidity language is used to code the proposed blockchain model and it is deployed in Kaleido. The authors of [21] proposed a Hyperledger fabric blockchain system to enhance Modbus, one of the Industrial Internet of Things IIoT protocols that faces many security challenges, such as SPOFs. On-chain authentication and authorization are supported by the designed decentralized identity system. By providing both security and scalability for Modbus connections, it can be used in a system with more than one organization. Self-sovereign Identity, blockchain, and Inter Planetary File technologies were used by [17] to improve food supply chains. By using SSI concepts, the study proposed a way to manage certifications throughout the supply chain. A certificate is issued by a certifying body and stored in IPFS, with only some key information being stored on the chain; verifiers need this information to verify whether a certificate is valid in the chain. To improve supply chain security, the authors in [18] also implemented a Hyperledger Fabric framework to ensure each registered device in the supply chain is tracked and to improve system security. Furthermore, reference [19] proposed a supply chain traceability system, though this proposed system tracks and validates both sides of the transaction. Additionally, reference [20] used a permissioned blockchain network in order to take advantage of smart contract features and to increase supply chain management security. The proposed framework provides the user with control over the data and increases identity protection by using cryptographic proof. In recent years, telehealth has become a necessity, especially since the COVID-19 pandemic started. In [31], the authors addressed the problem of trusting e-health application service providers and not knowing whether they comply with regulations to ensure privacy and security.