## 1 Introduction
This paradigm offers opportunities to improve privacy, security, and process efficiency in multiple sectors, thanks to the greater control it gives individuals over their personal information. For example, banks can use this paradigm to simplify customer onboarding processes, and governments can use this paradigm to improve citizen authentication, streamline online services and ensure personal data protection, or to issue and verify certificates and diplomas digitally, reducing fraud. In the healthcare sector, an SSI allows for the secure and private management of patients' personal information, facilitating data sharing between different healthcare entities and improving patient privacy, and in the IoT sector, an SSI can ensure that devices communicate securely and that users have control over the information they share. The model proposal presented in this article focuses on these last two sectors. Specifically, this article presents a smart healthcare model proposal that is based on an SSI to return the control of data to individuals and that relies on blockchains to ensure data integrity. Focused on the most innovative information technologies, this article aims to propose an identity management model for all healthcare professionals and all entities that are involved with healthcare facilities, such as patients or general practitioners, without neglecting that of the medical devices connected through IoT technology to healthcare systems, and whose number has grown further with the COVID-19 pandemic to limit patient movements and risks for medical personnel. Current data management in the healthcare system presents several challenges and issues, such as data security, interoperability among healthcare IT systems, data quality, and data access, which can affect the quality of care, patient safety, and operational efficiency. All healthcare institutions can be vulnerable to cyber attacks, and different IT systems often do not communicate with each other effectively, making it difficult to transfer and share information. In addition, a lack of standardization or errors in data entry can lead to the creation of incomplete, inaccurate, or outdated databases, and the access to data by medical personnel necessary to make informed decisions can be difficult, reducing the effectiveness of care and increasing the risk of medical errors. When investigating current data management in the healthcare system, we cannot ignore the data coming from IoT medical devices that are transforming the system by making it more efficient, accessible, and patient-centered, and all the challenges and issues associated with them. IoT medical devices can also be vulnerable to security breaches; the data collected by them must be treated in compliance with privacy regulations, and the quality and accuracy of the data must be guaranteed. Furthermore, to ensure the integration of data into a single healthcare information system, the use of common formats and protocols must be a priority. The proposal aims to manage a massive amount of health data coming from the healthcare digitization process and that represent invaluable sources of information, both for a better delivery of health services and for medical research and prevention. The model proposal takes into account the creation and exchange of any type of medical documentation, such as medical reports issued by a specialist after a visit or data collected by a precise medical device. The owner of such medical reports can share them with other doctors through their DDO, the service endpoint that allows us to create a secure connection by using a DIDcomm protocol. Such medical documentation is shared as verifiable credentials (VCs) or verifiable presentations (VPs), which represent key concepts of the SSI paradigm. All stakeholders share data through secure channels thanks to encryption.