A comprehensive survey on security, privacy and authentication in blockchain

In this paper, a comprehensive survey of security, privacy and authentication issues of blockchain is conducted. Additionally, a comparative analysis of existing security mechanisms that are adopted in literature to make the systems secure is presented. A brief survey of closely related survey papers is also provided after critically analysing their contributions and organisation. Besides, a mathematical equation is formulated to compute the recency score of a particular survey paper based on the number of recent papers included in it. Furthermore, critical analysis of the existing techniques and strategies is provided. In addition, the most frequently asked question by the researchers, i.e., when should we use blockchain?, is answered via an extended version of a decision tree. At the end, future research directions are provided to lay a solid research foundation for the upcoming researchers.