  Citation: Ghovanlooy Ghajar, F.; Sikora, A.; Welte, D. Schloss: Blockchain-Based System Architecture for Secure Industrial IoT. Electronics 2022, 11, 1629. https:// doi.org/10.3390/electronics11101629 Academic Editors: Junaid Arshad, Jonathan Loo and Omair Shafiq Received: 19 April 2022 Accepted: 18 May 2022 Published: 20 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). electronics Article Schloss: Blockchain-Based System Architecture for Secure Industrial IoT Fatemeh Ghovanlooy Ghajar * , Axel Sikora and Dominik Welte Institute of Reliable Embedded Systems and Communication Electronics (ivESK), Offenburg University of Applied Sciences, 77652 Offenburg, Germany; axel.sikora@hs-offenburg.de (A.S.); dominik.welte@hs-offenburg.de (D.W.) * Correspondence: fatemeh.ghovanlooy@hs-offenburg.de Abstract: Industrial companies can use blockchain to assist them in resolving their trust and security issues. In this research, we provide a fully distributed blockchain-based architecture for industrial IoT, relying on trust management and reputation to enhance nodes’ trustworthiness. The purpose of this contribution is to introduce our system architecture to show how to secure network access for users with dynamic authorization management. All decisions in the system are made by trustful nodes’ consensus and are fully distributed. The remarkable feature of this system architecture is that the influence of the nodes’ power is lowered depending on their Proof of Work (PoW) and Proof of Stake (PoS), and the nodes’ significance and authority is determined by their behavior in the network. This impact is based on game theory and an incentive mechanism for reputation between nodes. This system design can be used on legacy machines, which means that security and distributed systems can be put in place at a low cost on industrial systems. While there are no numerical results yet, this work, based on the open questions regarding the majority problem and the proposed solutions based on a game-theoretic mechanism and a trust management system, points to what and how industrial IoT and existing blockchain frameworks that are focusing only on the power of PoW and PoS can be secured more effectively. Keywords: security; trust management; authorization; authentication; blockchain; Industry 4.0; game theory 1. Introduction The Internet of Things (IoT) has fundamentally altered how individuals interact with their environment during the last several years [1]. However, it may also be used in indus- trial domains, such as machinery, control systems, and information systems, as part of the so-called Industrial Internet of Things (IIoT) [2]. The IIoT seeks to revolutionize conven- tional production and usher in an intelligent age of highly linked machines. Industrial data should be collected and then utilized to improve production performance and management efficiency. However, owing to the geographical dispersion of IIoT devices and the variance of standards, connectivity is difficult [1]. Additionally, there are concerns about the security of the device’s massive volume of data. Despite the technical challenges, a vast number of companies have embraced IIoT solutions as a way to enhance their operations. However, as was quickly discovered, one of the major problems with this approach is that these new technologies greatly increase the industrial environment’s exposure to cyberattacks [3]. Moreover, with the emergence of IIoT, the security vulnerabilities posed by it are even more devastating. As a distributed ledger and decentralized database, blockchain has the ability to establish a secure value exchange system. Due to its appealing characteristics, blockchain is an excellent option for use in IIoT systems [4]. Although IIoT and blockchain are two distinct technologies, their convergence represents a paradigm change that is predicted to boost industrial communication. Electronics 2022, 11, 1629. https://doi.org/10.3390/electronics11101629 https://www.mdpi.com/journal/electronics