# Blockchain-based Multifactor Authentication for Future 6G Cellular Networks: A Systematic Review
## 1 Introduction  
Blockchain technology involves recording information that makes it hard to change, cheat, or hack the system [1, 2]. An exciting aspect of blockchain is the application with authentication, which formulates a system with multiple layers of security and authentications [3]. Blockchain-based mechanisms solve authentication problems for distributed ledger technologies [4, 5, 6]. Still, a significant amount of work is required to assist with machine learning models to predict incoming attacks or security threats [7]. So, similarly, the 6G applications and cellular networks also have specific vulnerabilities, which need to be addressed through the application of blockchain-based multifactor authentication technologies [8]. As the former applications are mainly based on artificial intelligence Visible light communication (VLC) technology, both are significantly vulnerable when itcomes to encryption, malicious behavior, and data transmission, which can be considerably problematic [9; 10]. Blockchain technology can establish a creditworthy ecosystem among different participants in a non-trustable distributed environment. For example, in cybersecurity, the use cases of the blockchain depend on different security parameters that are applied for authentication, identification, and authorization in organizations which have also become penetrable [11]. After introducing the cloud-based applications and other extensive cloud-based technologies, the challenges of authentication are enhancing, presenting various challenges and threats to individuals and organizations. Moreover, the threats related to authentication, identity management, and access control security in different environments and organizations also serve as challenges to various industries [11]. Communications between devices and things that are enabled to receive and process information due to embedded computing components, such as the Internet of vehicles or the Internet of Things, are significantly impacted by the challenges of authentication and security. As a result of these threats, different studies have proposed some access control technologies to address the extensive authentication and security issues faced by organizations, individuals, and industries [12; 13]. Apart from the exchange of images, voices, and video-based information available in 5G cellular networks, the researchers are now focusing on the new dimensions of interactions that involve five senses of communication, including the ubiquitous instant communications, internet of skills, virtual or augmented reality, pervasive intelligence, wireless brain-computer interfaces, and holographic communications, leading towards the emergence of the distant environment [14; 15]. The researchers are now analyzing and focusing on smart communication in different sectors, including autonomous driving, industry Internet, remote learning sector, health care sector, smart cities provided by 5G networks, and the secured transactions sector [16]. However, the smart cities connected to 5G networks have faced some limitations concerning the networks' reliability, security, and speed. This has increased the focus of researchers and practitioners on the 6G network developments as it promises to overcome the issues of latency, speed, and security associated with prior networks [17; 18]. Various researchers and experts have envisioned the 6G wireless networks to provide data-intensive smart societies in the future, having a significant level of automation and seamless wireless network integration throughout the underwater area, to the ground, air, and space [19]. With significant enhancement and growth of the emerging multimedia applications and data traffic, the 6G wireless network is predicted to cater to 607 exabytes of data traffic by 2025 and, in 2030, around 5016 exabytes per month [13].