Received: 19 November 2020 Revised: 27 December 2020 Accepted: 28 December 2020 DOI: 10.1002/ett.4224 RESEARCH ARTICLE CTrust-RPL: A control layer-based trust mechanism for supporting secure routing in routing protocol for low power and lossy networks-based Internet of Things applications Temur ul Hassan 1 Muhammad Asim 1 Thar Baker 2 Jawad Hassan 1 Noshina Tariq 1 1 Department of Computer Science, National University of Computer and Emerging Sciences, Islamabad, Pakistan 2 Department of Computer Science, University of Sharjah, Sharjah, UAE Correspondence to: Muhammad Asim, Department of Computer Science, National University of Computer and Emerging Sciences, Islamabad, Pakistan. Email:muhammad.asim@nu.edu.pk Abstract Internet of Things (IoT) fostered a new epoch of innovation by interconnect- ing digital devices to make human life more convenient and attractive. These smart objects are largely deployed as low power and lossy networks (LLNs) and use routing protocol for LLNs (RPL) for routing. Unfortunately, it is extremely vulnerable to a large variety of external and internal attacks to cause devas- tating and calamitous effects. However, this article’s scope revolves around internal attacks only, where nodes are already part of a legitimate network. Var- ious trust-based mechanisms have been proposed to secure the RPL protocol from insider attackers. Existing trust mechanisms cause high energy depletion due to complex computation on the node level, which consequently decreases the performance of LLNs. Therefore, this article presents a novel hierarchical trust-based mechanism “CTrust-RPL” by assessing the trust of nodes based on their forwarding behaviors. This study ships complex trust-related computations to the higher layer, known as the controller, to save computational, storage, and energy resources at the node level. We also compare the proposed mechanism with a state-of-the-art technique called Sec-trust. Our mechanism demonstrates superior performance in detecting and isolating blackhole attacks. The results depict that CTrust-RPL detects and isolates 10% more malicious nodes than Sec-trust in the same time-lapse. The average packet loss ratio difference is less for our proposed mechanism, with 35% more energy efficiency. 1 INTRODUCTION Internet of Things (IoT) has become an essential part of our personal lives. It is emerging as an epoch of innovation, where devices belonging to digital and machine ecosystems are interconnected over the Internet to yield efficacy and conve- nience in academia, industries, and human lives. 1-3 Technologies like 5G and 6G enable the next generation of wireless communication systems in compliance with sophisticated techniques for security. 4,5 They support the huge IoT infras- tructures, which can be defined as a link, management, and communication of a large number of smart and sensing things (also known as objects). These things are capable of interacting with each other, especially, for transferring information in a network. 6-8 They are largely deployed as low power and lossy networks (LLN). The LLN is a class of networks where Trans Emerging Tel Tech. 2021;32:e4224. wileyonlinelibrary.com/journal/ett © 2021 John Wiley & Sons, Ltd. 1 of 20 https://doi.org/10.1002/ett.4224