I. Introduction
A digital identity is a set of attributes used to identify a particular user in order to gain access to resources and services in the digital world. This identity management process has been organised using a dedicated system called Identity Management (IDM), which is continuously evolving to fulfil the requirements of this domain. Originally, Centralised IDM systems reliant on a central authority were designed to provide services to small and closed environments [1]. This IDM was generally limited to an organisation and requires a separate identity for each organisation [2]. In this IDM, there was no inter-organisation accessibility available for the global interconnection, which led to the development of a new IDM model called Federated IDM system [3], wherein, an IDentity Provider (IDP) was responsible for managing an identity to provide single sign-on for many organisations by establishing the trust relationship [4]. However, this IDM system had some issues such as the control of an identity was still not with the user and the user details were stored at the identity provider [5]. This led to the development of a user-centric identity management system called Self-Sovereign IDM system, which replaced the traditional central authority with a distributed ledger and offered overall control of an identity and its related data to the user.