Decentralized Finance (DeFi), a blockchain powered peer-to-peer financial system, is mushrooming. One year ago the total value locked in DeFi systems was approximately 600m USD, now, as of January 2021, it stands at around 25bn USD. The frenetic evolution of the ecosystem makes it challenging for newcomers to gain an understanding of its basic features. In this Systematization of Knowledge (SoK), we delineate the DeFi ecosystem along its principal axes. First, we provide an overview of the DeFi primitives. Second, we classify DeFi protocols according to the type of operation they provide. We then go on to consider in detail the technical and economic security of DeFi protocols, drawing particular attention to the issues that emerge specifically in the DeFi setting. Finally, we outline the open research challenges in the ecosystem.

翻译：分散化金融(DeFi)是一连串权力的同侪对等金融体系(DeFi)正在蓬勃发展。一年前,DeFi系统锁定的总价值约为600万美元,现在,截至2021年1月,该价值约为25美元左右。生态系统的急剧演变使得新来者难以了解其基本特征。在这个知识系统化(SoK)中,我们沿着其主要轴线划定了DeFi生态系统。首先,我们概述了DeFi原始生态系统。第二,我们根据它们提供的业务类型对DeFi协议进行了分类。我们接着详细审议DeFi协议的技术和经济安全,特别提请注意DeFi环境中出现的问题。最后,我们概述了生态系统的开放研究挑战。