Censuses protocols is one of the blockchain framework architecture layer that is critical to the privacy of the technology. Therefore, any attempt to improve on privacy and Performance of blockchain technology will focus on the consensus layer. Understanding the consensus mechanism underly the layer is paramount. This paper focuses on two of the mainstream consensus mechanism; PoW and PoA with a comparison of the advantages and disadvantages of each of the consensus algorithm. The privacy of these algorithms has been evaluated based on the metrics selected from the existing literature. The paper used SLR research method. It consists of three activities: Planning, Execution, and reporting. The activities have several processes and steps that were undertaken. A total of 72 papers were selected for analysis and they were those published between 2019-2023. The review highlighted the wide range of application areas for PoW and PoA, including healthcare, IoT, and industry 4.0. However, PoW`s popularity seemed to decline due to the introduction of faster and more secure blockchain algorithms. Privacy was a common theme, with decentralization, strong encryption, mutability, and scalability being key factors discussed in various studies. Overall, the systematic literature review Future Directions: Future research on PoW should focus on addressing concerns related to diminishing algorithm rewards and incentives for participants. Scholars should put effort in development of more hybrid algorithms that combine PoW with other blockchain algorithms to overcome challenges and gain benefits. In addition, the authors propose that more studies to focus on improving performance of PoA and explore on defining more decentralized algorithms.

Proof of Work, Proof of Stake, Proof Action, Privacy, Blockchain, performance

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