# Blockchain-Based Decentralised Authentication in Closed Environments
###### Abstract  
Traditional authentication systems with an authentication server that handles authentication requests from many clients have a major weakness, i.e., a single point of failure. This study presents an authentication paradigm based on blockchain, which provides a decentralised and distributed mechanism for processing authentication. The security of the proposed design of the decentralised authentication protocol was evaluated using Gong-Needham-Yahalom (GNY) logic. The results indicated that the protocol was secure against various attacks. This protocol has significant potential for enhancing secure identity management in sectors where privacy and data integrity are most important.  
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To reduce the risk of the centralised authentication server being compromised, leading to the failure of the authentication system, existing research has attempted to apply distributed technologies or decentralisation to assist with the authentication process [5]. In recent years, the concept of decentralisation has gained popularity as a solution to the limitations of centralised systems. Decentralisation refers to the distribution of authority and data across multiple entities in a network rather than relying on a single central authority. In the context of authentication, this approach differs from traditional centralised systems, where user credentials are stored and verified by a single server, creating potential vulnerabilities, including single points of failure. In contrast, decentralised systems reduce these risks by distributing authority and data across multiple nodes. Thus, the system becomes more resilient to node failures and attacks.  
Blockchain is a technology that primarily operates on the concept of decentralisation [6]. However, although blockchain technology operates in a decentralised and distributed manner, existing research does not fully utilise its capabilities. In other words, a blockchain has only been used as a database to store authentication credentials, with one server attached to the blockchain acting as the authentication server. This implies that the problem of a single failure point persists.  
Therefore, this study designed an authentication system that fully utilised the decentralisation capability of blockchain technology to overcome the aforementioned challenges and limitations of existing blockchain-based approaches. Currently, blockchain is more than a platform for cryptocurrencies. This technology supports the creation and execution of application systems without the need for a central authority. By incorporating blockchain into the proposed design of the authentication protocol, a decentralised mechanism for processing authentication can be accomplished. This allows every node in the blockchain network to perform authentication verification without using a central authentication server. As a by-product of using a blockchain, every authentication property is recorded in the blockchain and can therefore be tracked if needed in the future.  
The proposed decentralised authentication protocol differs from other blockchain-based protocols in two ways. First, the proposed protocol improves the reliability of authentication operations through blockchain decentralisation. This solves the problem of a single failure point. Second, authentication transactions are made transparent through a blockchain consensus mechanism and traceability. We also provide proof of security for the proposed protocol by using Gong-Needham-Yahalom (GNY) logic to ensure that the protocol is not prone to attacks such as replay and man-in-the-middle attacks.  
Our study contributions are described as follows. First, we explored and designed a novel authentication protocol that applied blockchain technology to achieve decentralisation. Second, we provided a new authentication method that overcame existing problems, such as a single point of failure. Third, we analysed and proved the security of the proposed protocol using GNY logic.