# Blockchain-based Multifactor Authentication for Future 6G Cellular Networks: A Systematic Review
## 6 Recent Exploration of MFA Applications and Blockchain Authentication
[96] and uses an adaptable and decomposable 3-factor authentication system that can be applied simultaneously to ensure efficiency and speed. The tests on this system showed that it could provide an ideal efficiency in terms of transparency of action, security, and speed. However, further testing and real-time application are required. [PERSON] et al. [98] also presented a 3-factor authentication scheme to ensure a high-security environment for communicating parties and integrates biometrics, password, and smart card authentication into a single system. Multiple server technologies are used to ensure that performance is quick and transparent. However, the technique still poses a communication cost. There is limited research on the integration of multifactor analysis in blockchain-based applications. However, some papers were reviewed that can be valuable to indicate the benefits of these integrations. [PERSON] et al. [32] presented a multifactor analysis named 2 FA for WordPress pages by using Hydro Raindrop multifactor authentication technology. In this paper, the researcher summarized the use of a blockchain-based two-factor authentication solution by a page on WordPress that contributes to securing user information. The study is not experimental, however, and the entire proposal is based on other theoretical and practical evidence. Overall, it suggested that the use of a decentralized technique provided by the integration of blockchain can enable multifactor and transparent user authentication, strengthening the security of information and the assets of individuals. Several studies also indicate the use of blockchain-based authentication procedures for autonomous vehicles [99; 100; 101]. In the study by [PERSON] et al. [10], Blockchain-assisted privacy-preserving authentication system (BPAS) is presented to secure the data generated by vehicular ad hoc networks. This technique was proposed for ensuring accuracy as well as trust in the systems. However, there was a lack of support for batch verification in this paper that could provide an optimized verification in the form of blocks of data and hence reduce load on the resource consumption. [PERSON] et al. [15] also proposed an MFA based on Blockchain technology that proposed the use of an embedded Digital Signature (MFBC_eDS) that was found to be a suitable technique for countering the adversarial attacks on the Internet of vehicles in the past. [PERSON] et al. [8] proposed a framework for authentication based on Blockchain technology as they claimed it could add more security to the authentication process. In this framework, the one-time password (OTP) is encrypted and sent to the application/website to complete the authentication process. This system was claimed to be safer than SMS-based authentication mechanisms, but it was less efficient in terms of time efficiency. [PERSON] et al. [11] proposed an out-of-band 2 factor authentication mechanism for IoT devices by use of blockchain to enable flexible, secure, and reliable authentication [102; 103; 104; 105; 106]. The overheads of blockchain use, however, were high. Table 4 summarizes all the studies related to MFA and Blockchain.