On securing IEEE 802.15.4 networks through a standard compliant framework Savio Sciancalepore, Giuseppe Piro, Elvis Vogli, Gennaro Boggia, and Luigi Alfredo Grieco Department of Electrical and Information Engineeering (DEI) Politecnico di Bari, Italy Email: {name.surname}@poliba.it Abstract—The IEEE 802.15.4 standard is widely recognized as one of the most successful enabling technologies for short range low rate wireless communications. Although it provides all the details of both MAC and PHY layers of the protocol stack, the standard also explains specific methodologies to protect MAC packets through symmetric-key cryptography techniques under several security options. However, the orchestration of available security profiles and the management of key negotiation schemes is delegated to upper layers. In support of this feature, this work describes a standard compliant security framework aimed at proposing: (i) different kind of security architectures, (ii) an efficient mechanism for initializing a secure IEEE 802.15.4 domain, and (iii) a lightweight mechanism to negotiate link keys among devices. Experimental tests have been conducted to demonstrate the behavior of the proposed solution in real environments. Obtained results clearly show that the enabling of security features in constrained nodes requires additional computational efforts, which involve a not negligible growth of communication latencies. Such findings have to be carefully considered when designing and developing enhanced applications in future and secured Internet of Things (IoT) systems. Keywords—IoT, IEEE 802.15.4, security, key negotiation, ex- perimental evaluation I. I NTRODUCTION The Internet of Things (IoT) paradigm refers to a system where different objects (i.e., sensors, machines, vehicles, smart phones, tablets, motes etc.) realize a capillary networking infrastructure connected to the Internet [1], thus offering the opportunity to develop many novel pervasive services in a number of application domains, like health care, smart city, energy management, military, environmental monitoring, industry-automation [2][3]. Such evident potentials have driven researchers, industries, and standardization bodies to define novel and efficient protocol stacks, which are more suitable for constrained devices [2][4][5]. Among of all the most important proposals, the IEEE 802.15.4 standard is widely recognized as one of the most successful enabling technologies for short range low rate wireless communications and provides all the details for both MAC and PHY layers [6]. More recently, the IEEE 802.15.4e specification introduced some amendments to the aforemen- tioned standard, among which we can consider the Time- Slotted Channel Hopping (TSCH), i.e., a novel MAC protocol properly designed to better support multi-hop communications in industrial applications [7][8]. However, to actualize the IoT vision and easy plug and play operations of smart devices in IPv6 networks, if properly combined in a communication stack for Low-power and Lossy Networks (LLNs) based on IEEE 802.15.4 radios, the Internet Engineering Task Force (IETF) has recently proposed and standardized novel interesting pro- tocols at different layers of the protocol stack (i.e., for taking into account several issues, like routing [9], compression [10], security [8], and so on). The risks arising from a potential lack of security and privacy of the involved stakeholders could actually hinder the deployment of the IoT. To overcome such an issue, several solutions have been introduced in both IEEE and IETF contexts and in literature (Tab. I reports a summary of the most important proposals). First, the IEEE 802.15.4 specification allows the possibility to protect MAC packets by means of symmetric-key cryptography techniques, based on the AES- CCM* algorithm, with several security options. Nevertheless, it does not explain how to handle the initialization of a secure IEEE 802.15.4 domain, the generation and the exchange of keys, and the management of joining operations in a secure 802.15.4 network already configured in the past. While a prac- tical solution devoted to the distribution of keys in 802.15.4 networks has been conceived within the ZigBee IP specifi- cation, a number of scientific publications have suggested, so far, to adapt well-known security solutions, already highly exploited in conventional IP networks, to the IoT domain, as well as specific implementation of Key Management Protocols (KMPs) more suitable for LLN domains. In addition, very valuable proposals have been formulated in various IETF working groups focusing on different layers of the protocol stack of a LLN. Unfortunately, at the time of this writing, such works are still in progress or they have not been yet translated in implementations on real testbeds, thus preventing the demonstration of their universal effectiveness. To provide a significant breakthrough in this direction, we developed a simple and standard compliant framework supporting a number of security features in the IEEE 802.15.4 MAC (this work has been presented in its preliminary ver- sion in [11] and [12]). The code is open-source and freely available from http://telematics.poliba.it/security-iot. It covers: (i) the identification of potential security configurations that could be supported in an IoT domain, (ii) the definition of schemes enabling the data confidentiality and integrity protec- tion of messages, (iii) the design of an efficient mechanism to configure and maintain a secured IoT domain, and (iv) the development of a lightweight KMP used by smart objects to negotiate link keys. Moreover, to demonstrate its concrete effectiveness, this novel proposal has been also implemented in the well known OpenWSN stack [13] and experimental tests