Evaluating DAG-Based Blockchains for IoT

Blockchain has been considered as the enabler to provide automated and trust-less Internet of things (IoT) services. However, legacy consensus mechanisms applied in most of the blockchain networks pose obstacles for deployment in IoT in respect of decentralization and scalability. The emerging Directed Acyclic Graph (DAG)-based models aim at delivering the benefits of blockchain without making compromise on performance. This paper gives a critical analysis on the two representative DAG-based models, IOTA and Hashgraph. In particular, we provide an insightful overview of the two blockchains, with their features and functionalities. We define desired criteria for evaluating these two blockchains, provide an in-depth analysis on the two systems, and identify open challenges IOTA and Hashgraph are facing for their application in IoT.