A decentralized API registration and discovery system on the Ethereum blockchain utilized for smart cities

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Παππάς, Θωμάς

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The rapid emergence of the Internet of Things (IoT) technology has prospered the concept of smart city, which refers to an urban area that facilitates the coexistence of people, organizations, environment and technology. IoT plays a major role, as it enables the sensing of physical events that occur, along with actuating on various objects in a city, thus granting valuable information and services for the citizens. Usually, the architecture of a smart city IoT implementation can be conceptualized in five distinct layers. The realization of IoT in smart cities faces a significant obstacle in the form of interoperability challenges inside and between these five layers. Interoperability denotes the capacity of various systems to communicate and exchange data smoothly, without requiring manual intervention. The absence of interoperability between IoT devices and software systems can lead to information silos, wherein data cannot be accessed or utilized by other systems. This thesis focuses on the discoverability of Layer 3 platform systems by Layer 4 applications, without prior knowledge of them, in a complex city scenario. Layer 3 platforms abstract the sensor and networking layers from the end-user applications and are responsible for the registration, discovery and management of devices (sensors, actuators), security, semantics and communication management with other software systems. Generally, platforms expose RESTful northbound APIs, so applications can onboard and receive data and functionality. The proliferation of these APIs is a prominent issue and a common place for the accumulation of the API specifications of the platforms is necessary. After examining the importance of transparency of operations in a collaborative environment such as a smart city, the utilization of Peer-to-Peer systems is unfolded. Taking into consideration the advantages, but also the limitations of blockchain networks, the solution proposed is a decentralized API Directory that can be deployed in any Ethereum Virtual Machine (EVM) compatible public or private blockchain. This API Directory can be used as a common place for smart-city IoT platforms to publish their API specifications, formulated on the OpenAPI specification standard, and for end-user applications to discover them based on location and desired category. Finally, a smart parking use case is demonstrated as a proof of concept for the system.



Blockchain network, Internet of Things (IoT), API directories, Smart cities