###### Abstract
Concerns regarding the security and privacy of users' identities were substantial, and several attacks on centralised systems were observed, which encouraged the exploration of decentralised identity management. Blockchain, being decentralised and one of the safest ways to process transactions anonymously, distributes control across a network of nodes. This decentralised method reduces the risk of a single point of failure and has proven to be more secure and resilient against cyberattacks and system failures [7]. The control and  
Figure 1: Timeline of Evolution of Identity and Authentication Methods. authentication process is distributed across a network of autonomous nodes (participants), ensuring that no single party controls the system. Additionally, because blockchain is immutable--meaning that data, once written, cannot be altered--it adds another layer of security against fraud, data tampering, and illegal access [2; 6]. This approach is more user-centric, giving users full control over what data they want to share and how much. Platforms such as uPort, Hyperledger Indy, and EverID have made significant progress in this area and will be discussed in detail in the upcoming sections of this paper. Companies like EarthID and Yoti (using similar decentralised methods for identity management) have gained popularity in the UK for consumer-facing and practical identity verification solutions, which are used daily across sectors such as retail, social media, finance, and the government. Their use cases include age verification, KYC, and event check-ins. Yoti, for example, is used by several large organizations, including big banks for biometric identity verification, national postal services for digital identity verification, popular social media platforms, and some nightclubs where age verification (18+) is required. Users can verify their identity or age (e.g., proving they are 18+) without sharing unnecessary details, such as their exact date of birth. Despite these advantages, decentralised authentication systems have struggled to gain widespread acceptance, particularly in real-time organizational settings. Implementing decentralised identity management systems necessitates significant infrastructure upgrades and financial investments. In addition to establishing the decentralised infrastructure, organizations must also provide staff with the necessary training to properly manage and operate these systems. This can be a costly and time-consuming process, especially for companies that are already heavily invested in centralised identity management systems [8]. Moreover, many existing applications and systems are designed with centralised architectures in mind, making the integration of decentralised authentication mechanisms a complex and challenging task. Careful planning and execution are required to ensure a smooth transition from centralised to decentralised systems [9]. While decentralised identity management systems offer superior security and resilience, they are not without risks. For example, blockchain networks are vulnerable to 51% attacks, where a group of malicious nodes gains control over the majority of the network's computational power, allowing them to manipulate transactions and potentially compromise the system's integrity [10]. As a result, even decentralised systems require continuous monitoring and updates to protect against emerging threats. This underscores the importance of having a robust and adaptable identity management infrastructure, regardless of whether the system is centralised or decentralised. This comparative study of centralised and decentralised authentication systems reveals distinct advantages and challenges with each approach. Centralised systems, which have been used for decades, are easier to implement and have evolved to address many security concerns. However, they remain vulnerable to scalability issues, privacy risks, and single points of failure.