Abstract
LoRaWAN (Long Range Wide Area Network) is a Low-Power Wide Area Networks (LPWAN) technology with very rapid uptake during the previous years, developed by the LoRa (Long Range) Alliance as an open standard operating over the unlicensed band. Current LoRaWAN architecture foresees specific techniques for bootstrapping end-to-end encryption during network initialization. In particular, this work focuses on the Over-The-Air Activation (OTAA) method, which uses two keys (Network key (NwkKey) and Application key (AppKey)) that are hard-coded into the device and do not change throughout the entire lifetime of the deployment. The inability to refresh these two keys is as a weak point in terms of the overall security of the network especially when considering deployments that are expected to operate for at least 10–15 years. In this paper, the security issues of OTAA are presented in detail highlighting the vulnerabilities against the specific type of attacks. A new scheme for network activation is proposed that builds upon the current LoRaWAN architecture in a way that maintains backwards compatibility while resolving certain vulnerabilities. Under the new mechanism, the devices periodically negotiate new keys securely based on elliptic-curve cryptography. The security properties of the proposed mechanism are analyzed against a specific type of attacks. The analysis indicates that the new secure rejoin mechanism guarantees (i) computational key secrecy, (ii) decisional key secrecy, and (iii) key independence, forward and backward, for both root keys thus properly addressing the considered security vulnerabilities of LoRaWAN. Moreover, the method is implemented in software using the RIOT-OS, a hardware-independent operating system that supports many different architectures for 8 bit, 16 bit, 32 bit and 64 bit processors. The resulting software is evaluated on the FIT IoT-Lab real-world experimentation facility under a diverse set of ARM Cortex-M* devices targeting a broad range of IoT applications, ranging from advanced wearable devices to interactive entertainment devices, home automation and industrial cyber-physical systems. The experiments indicate that the overall overhead incurred in terms of energy and time by the proposed rejoin mechanism is acceptable given the low frequency of execution and the improvements to the overall security of the LoRaWAN1.1 OTAA method.
Highlights
The need to deliver scalable and long-term networks of devices that integrate sensing, computation and wireless communication in small, low-power devices that can be seamlessly embedded in complex physical indoor and outdoor environments has given rise to sub-GHz wireless communication [1,2]
This paper looks into the Over-The-Air activation of end devices, the proposed mechanism does not look into how the keys are stored within the Network/Application Servers
Since this paper looks into the key agreement process between the end-device and the Join/Application Server, it is assumed that the goal of a potential attacker is to collect any information that will be useful when trying to guess the session and integrity keys used to encrypt the communication between the end-devices and the application server
Summary
Elliptic-Curve Cryptography. J. Sens. Academic Editors: Lei Shu, Mário Alves, Adnan Al-Anbuky, Joel José Puga Coelho Rodrigues and Stefan Fischer Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Licensee MDPI, Basel, Switzerland. 4.0/).
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