Secure smart contract-based digital twins for the Internet of Things

The proliferation of Internet of Things (IoT) devices that operate unattended providing a multitude of important and often sensitive services highlights the need for seamless interoperability and increased security. We argue that digital twins of IoT devices, with the right design, can enhance the security, reliability, auditability, and interoperability of IoT systems. The salient features of digital twins have made them key elements for the IoT and Industry 4.0. In this paper, we leverage advances in W3C's Web of Things (WoT) standards and distributed ledger technologies (DLTs) to present a novel design of the smart contract-based digital twins with enhanced security, transparency, interoperability, and reliability. We provide two different variations of that general design using two different blockchains (one public and one private, permissioned blockchain), and we present design trade-offs. Furthermore, we introduce an architecture for accessing and controlling IoT devices securely and reliably, providing full auditability, while at the same time using the proposed digital twins as an indirection mechanism (proxy). The proposed architecture leverages the blockchain to offer notable properties, namely,decentralization, immutability, auditability, non-repudiation, availability, and reliability. Moreover, it introduces mass actuation, easier management of IoT devices, and enhanced security to the IoT gateways, enables new business models, and makes consumer devices (vendor-)agnostic.