Blockchain is a technology making the shared registry concept from distributed systems a reality for a number of application domains, from the cryptocurrency one to potentially any industrial system requiring decentralized, robust, trusted, and automated decision making in a multi-stakeholder situation. Nevertheless, the actual advantages in using blockchain instead of any other traditional solution (such as centralized databases) are not completely understood to date, or at least there is a strong need for a vademecum guiding designers toward the right decision about when to adopt blockchain or not, which kind of blockchain better meets use-case requirements, and how to use it. In this paper, we aim at providing the community with such a vademecum, while giving a general presentation of blockchain that goes beyond its usage in Bitcoin and surveying a selection of the vast literature that emerged in the last few years. We draw the key requirements and their evolution when passing from permissionless to permissioned blockchains, presenting the differences between proposed and experimented consensus mechanisms, and describing existing blockchain platforms.

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关于区块链技术的 Vademecum：何时、何地以及如何

区块链是一种技术，使分布式系统中的共享注册表概念成为许多应用领域的现实，从加密货币到可能需要在多利益相关者情况下进行分散、稳健、可信和自动化决策的任何工业系统。然而，迄今为止，使用区块链而不是任何其他传统解决方案（例如集中式数据库）的实际优势尚未完全了解，或者至少强烈需要 vademecum 指导设计人员正确决定何时采用区块链或不是，哪种区块链更能满足用例需求，以及如何使用它。在本文中，我们旨在为社区提供这样的 vademecum，同时对超越其在比特币中的使用范围的区块链进行一般性介绍，并调查了过去几年出现的大量文献。我们绘制了从无许可区块链到许可区块链的关键要求及其演变，展示了提议的和实验的共识机制之间的差异，并描述了现有的区块链平台。