Survey of Directed Acyclic Graph Based Blockchain Technology

Blockchain technology has been widely used in finance, public services, the Internet of Things(IoT), network security, supply chains, and other fields.However, the traditional blockchain with a single chain structure has some deficiencies in throughput, transaction confirmation speed, and scalability, which makes it difficult to apply it in some short-term and high concurrency data scenarios.In this paper, the Directed Acyclic Graph(DAG) based blockchain technology has attracted extensive attention and studied by scholars because of its advantages, such as concurrent transaction confirmation, high throughput, and strong scalability.By analyzing and studying the development and evolution, evaluation methods, optimization direction, and application scenarios of the existing DAG based blockchains, this paper explores the feasibility of DAG based blockchains in landing applications.Through the development of a mainstream DAG based blockchain, it compares the advantages and disadvantages of traditional blockchains and DAG based blockchains, analyzes the existing blockchain attribute evaluation methods, and summarizes the current DAG based blockchain evaluation results.On this basis, this paper summarizes the optimization methods of the existing DAG based blockchain from the aspects of transaction confirmation speed, system throughput, system security, and storage structure, and summarizes the application of a DAG based blockchain in data management, data sharing based on edge computing and federated learning, and data security for access control and privacy protection.Finally, it points out the main problems and challenges in the current studies, and provides further research directions.