## 2 Materials and Methods
The key distinctions among these methods pertain to the algorithm's complexity, criteria weighting techniques, the representation of preference evaluation criteria, the handling of uncertain data, and the type of data aggregation. Furthermore, each type of MCDM method comes with its specific merits and drawbacks that need detailed explanation based on the methodology. The reference architecture for blockchain technology includes the consensus layer. This layer manages the consensus between the nodes of the network and ensures that the state of the ledger is agreed upon by all nodes. It includes consensus protocols that are used to establish and maintain consensus, as well as to ensure network security, accuracy, and security of the ledger. Consensus can significantly affect the performance and security of a blockchain system. There are currently over a thousand initiatives in the field of blockchain technology, including over a hundred different consensus protocols. In recent years, there has been a noticeable increase in publications devoted to blockchain and distributed ledger technologies. Given that consensus mechanisms are a core aspect of these systems, it is not surprising that an increasing number of studies have been devoted to the design, evaluation, comparison, and selection of consensus protocols. For example, studies such as [4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16], have reviewed, analyzed, and compared various consensus protocols using various criteria. These works provide a comprehensive understanding of the characteristics of the protocols and the factors affecting their performance and security. And, to understand and analyze this huge number of consensus algorithms, researchers create their own classifications, taxonomies, and ontologies. Several works appeared recently in the literature, where different MCDM approaches were used in the field of DLT and blockchain, mainly for the choice of the blockchain platform, but also for the choice of the consensus protocol, for example [6; 19; 20; 21]. In Ref. [6] [PERSON] (2021) introduced the Boolean decision tree (BDT) technique-based framework based on the results of the classification framework introduced in the article. The proposed decision process starts with the accessibility of the blockchain following the design, performance, and security choices. In Ref. [19] [PERSON] (2020) et al. proposed a new approach to selecting blockchain consensus algorithms using multi-criteria decision-making (MCDM). The authors began by conducting a thorough review of the existing literature on blockchain consensus, identifying the various criteria used to evaluate consensus protocols. From this review, they identified the most important criteria and used a pairwise comparison technique to assign weights to each criterion. They then used a traditional benchmarking technique to compare ten consensus algorithms using a set of criteria in two parts. However, this study was only a starting point for an end-to-end MCDM approach, as further steps were required to define criteria values, select appropriate MCDM techniques, analyze results, and provide guidance for practitioners. In Ref. [21] [PERSON] et al. (2022) developed a MCDM framework to help select the most appropriate consensus protocol for a blockchain system based on its specific requirements. The authors viewed the consensus protocol ranking process as a MCDM problem that evaluated different alternatives (protocols) using decision criteria (features) and considering the defined weights (priorities) by decision-makers (experts). They gathered quantitative and qualitative data on 18 state-of-the-art consensus protocols from various sources and combined it into an open-source data repository. They demonstrated the potential of the framework by using the collected data set to identify the best consensus protocols for public, consortium, and private blockchains. Furthermore, the authors used the pro posed framework to determine the most suitable consensus protocol for a blockchain-based bike renting system.