Leveraging Blockchain for Device Registration and Authentication in tSIP-Based Phone-of-Things (PoT) Systems

Phone of Things (PoT) is a new paradigm in IoT that has been recently coined in the literature. PoT provides a framework for leveraging the ubiquitous phone network assets and infrastructure by making them part of the IoT architecture to manage and control IoT gadgets. PoT proposes a lightweight SIP-based messaging protocol, which we call tSIP, that we can map to its corresponding original SIP protocol messages with the help of a proxy (i.e., the PoT gateway). tSIP facilitates communication between resource-constrained smart objects and the communication server using mature phone technologies with abstractions that people are already familiar with. In this context, the paper proposes a lightweight decentralized registration and authentication mechanism based on blockchain technology for smart gadgets in the PoT system to facilitate their association with the communication server. The proposed mechanism provides a secure, trustless, and scalable environment for PoT without requiring high-end communication servers, affecting the existing SIP-based VoIP architecture, or mandating trust in third-party entities. The proposed mechanism uses the Ethereum blockchain and smart contracts to implement a programmatic, immutable access control mechanism to administer the association of IoT devices with the communication server. As a proof of concept, we provide a prototype implementation of the proposed mechanism using a private blockchain due to its privacy characteristics, fast transaction processing, and cost-effectiveness. We conduct a feasibility study of the proposed mechanism and a security analysis. The analysis demonstrates that the proposed mechanism complies with the security standards of the SIP protocol and fits the constraints of embedded smart objects.