Research Article Low-Cost Authentication Protocol for D2D Communication in m- Health with Trust Evaluation Ana Paula G. Lopes and Paulo R. L. Gondim Electrical Engineering Department, University of Brasilia, Brasília, Distrito Federal, Brazil Correspondence should be addressed to Paulo R. L. Gondim; prgond@gmail.com Received 24 May 2020; Revised 9 August 2020; Accepted 16 September 2020; Published 27 October 2020 Academic Editor: Yujin Lim Copyright © 2020 Ana Paula G. Lopes and Paulo R. L. Gondim. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Relay-assisted device-to-device (D2D) communication serves users at the edge of system coverage of 5G networks, enabling communication among sensors and patients’ mobile devices, and improving spectral and power efficiency. The security of D2D- based m-health applications requires attention due to the delicacy of the data treated in the collection, transmission, and storage of information on patients, whose devices must be adequately authenticated. However, traditional authentication and key agreement schemes are not suitable for D2D scenarios, since they might expose patients to security vulnerabilities and lead to an excessive use of resources. This article proposes a secure and lightweight scheme based on Shamir secret sharing for the mutual authentication of m-health devices in relay-assisted D2D communications, which provides security robustness and reduces resources (energy, processing) consumption. The manuscript also addresses the trustworthiness of devices involved in data relay and device discovery procedures. 1. Introduction Mobile device communication has grown over the past few years due to the development of thousands of new applica- tions and devices. The Internet of Things (IoT), the main responsible actor for such a revolution, enables the connec- tion of several applications (e.g., those based on smart- phones, smart watches, smart TVs, smart homes and vehicles, and smart metering). Mobile-health (m-health), which is an interesting human health-related application, provides the monitoring and evaluation of vital signs and other important health information on patients, preventing the escalation of diseases and affording immediate relief in emergencies. The m-health system commonly works with a group of sensors coupled to a patient’s body and a mobile device that receives the measurements from such sensors and sends the information to the respective health center. Huang et al. [1] observed high-quality healthcare services, such as remote monitoring, mobile telemedicine, remote disease diagnosis, and emergency care require the assurance of security of both the system and the communication channels through which messages are exchanged. On the other hand, D2D communication refers to direct and low-power communication between two mobile devices [1]; it offers services based on their proximity, and its advan- tages include higher throughput, low latency, and instanta- neous communications between devices [2]. Moreover, trafficoffloading/traffic steering between cellular and D2D networks is an excellent alternative for the bandwidth demands imposed over cellular networks, increasing spectral efficiency, and reducing energy consumption [1]. Device-to-device communication (D2D) is a strong can- didate for communication of devices involved in m-health applications. For example, in a scenario of remote telemoni- toring of patients implemented on a large scale by cellular and wireless body area networks (WBAN), the high volume of data exchanged, jointly with concurrent data traffic from other applications, requires a new perspective on the com- munication of near devices for providing important health information on patients’ health, 24 hours a day and seven days a week. As another example, in emergency care Hindawi Wireless Communications and Mobile Computing Volume 2020, Article ID 8876807, 16 pages https://doi.org/10.1155/2020/8876807