Cryptocurrency Solutions to Enable Micropayments in Consumer IoT

The successful amalgamation of cryptocurrency and consumer Internet-of-Things (IoT) devices can pave the way for novel applications in machine-to-machine economy. However, the lack of scalability and heavy resource requirements of initial blockchain designs hinder the integration, and it is unclear how consumer devices will be adopting cryptocurrency. Therefore, in this article, we critically review the existing integration approaches and cryptocurrency designs that strive to enable micropayments among consumer devices. We identify and discuss solutions under three main categories; direct integration, payment channel network, and new cryptocurrency design. The first approach utilizes a full node to interact with the payment system. Offline channel payment is suggested as a second-layer solution to solve the scalability issue and enable instant payment with low fee. New designs converge to semicentralized scheme and focus on lightweight consensus protocol that does not require high computation power. We evaluate the pros and cons of each of these approaches and then point out future research challenges. Our goal is to help researchers and practitioners to better focus their efforts to facilitate micropayment adoptions.