In Industrial IoT (IIoT) environments and especially for applications relying on Mobile Nodes (MNs), ensuring communication security is a critical requirement, in order to prevent attacks that aim to obtain sensitive data or compromise MNs. In this paper, we focus on the security of IIoT systems based on the 6TiSCH architecture defined by the IETF, in the presence of node mobility. We propose a method for provisioning key material to MNs, enabling the enforcement of a trade-off between security and overhead. Specifically, we consider three security settings, characterized by different security levels and communication/storage overhead. For each setting, we evaluate the impact on performance through simulation. Finally, we provide a set of guidelines to help network operators in the selection of the setting to use.

The Constrained Application Protocol (CoAP) is a major application-layer protocol for the Internet of Things (IoT). The recently standardized security protocol Object Security for Constrained RESTful Environments (OSCORE) efficiently provides end-to-end security of CoAP messages at the application layer, also in the presence of untrusted intermediaries. At the same time, CoAP supports one-to-many communication, targeting use cases such as smart lighting and building automation, firmware update, or emergency broadcast. Securing group communication for CoAP has additional challenges. It can be done using the novel Group Object Security for Constrained RESTful Environments (Group OSCORE) security protocol, which fulfills the same security requirements of OSCORE in group communication environments. While evaluations of OSCORE are available, no studies exist on the performance of Group OSCORE on resource-constrained IoT devices. This article presents the results of our extensive performance evaluation of Group OSCORE over two popular constrained IoT platforms, namely Zolertia Zoul and TI Simplelink. We have implemented Group OSCORE for the Contiki-NG operating system and made our implementation available as open source software. We compared Group OSCORE against unprotected CoAP as well as OSCORE. To the best of our knowledge, this is the first comprehensive and experimental evaluation of Group OSCORE over real constrained IoT devices.

The 6TiSCH architecture has been gaining attraction as a promising solution to ensure reliability and security for communication in applications for the Industrial Internet of Things (IIoT). While many different aspects of the architecture have been investigated in literature, an in-depth analysis of the security features included in its design is still missing. In this paper, we assess the security vulnerabilities of the 6top protocol, a core component of the 6TiSCH architecture for enabling network nodes to negotiate communication resources. Our analysis highlights two possible attacks against the 6top protocol that can impair network performance and reliability in a significant manner. To prove the feasibility of the attacks in practice, we implemented both of them on the Contiki-NG Operating System and tested their effectiveness on a simple deployment with three Zolertia RE-Mote sensor nodes. Also, we carried out a set of simulations using Cooja in order to assess their impact on larger networks. Our results show that both attacks reduce reliability in the overall network and increase energy consumption of the network nodes.

The MAC standard amendment IEEE 802.15.4e is designed to meet the requirements of industrial and critical applications. In particular, the Time Slotted Channel Hopping (TSCH) mode divides time into periodic, equally sized, slotframes composed of transmission timeslots. Then, it combines time slotted access with multichannel and channel hopping capabilities, providing large network capacity, high reliability, and predictable latency while ensuring energy efficiency. Since every network node considers the same timeslots at each slotframe and selects physical channels according to a periodic function, TSCH produces a steady channel utilization pattern. This can be exploited by a selective jammer to entirely thwart communications of a victim node in a way that is stealthy, effective, and extremely energy efficient. This article shows how a selective jamming attack can be successfully performed even though TSCH uses the IEEE 802.15.4e security services. Furthermore, we propose DISH, a countermeasure which randomly permutes the timeslot and channel utilization patterns at every slotframe in a consistent and completely distributed way without requiring any additional message exchange. We have implemented DISH for the Contiki OS and tested its effectiveness on TelosB sensor nodes. Quantitative analysis for different network configurations shows that DISH effectively contrasts selective jamming with negligible performance penalty.

Time division multiple access (TDMA) is often used in wireless sensor networks (WSNs), especially for critical applications, as it provides high energy efficiency, guaranteed bandwidth, bounded and predictable latency, and absence of collisions. However, TDMA is vulnerable to selective jamming attacks. In TDMA transmission, slots are typically pre-allocated to sensor nodes, and each slot is used by the same node for a number of consecutive superframes. Hence, an adversary could thwart a victim node's communication by simply jamming its slot(s). Such attack turns out to be effective, energy efficient, and extremely difficult to detect. In this paper, we present JAMMY, a distributed and dynamic solution to selective jamming in TDMA-based WSNs. Unlike traditional approaches, JAMMY changes the slot utilization pattern at every superframe, thus making it unpredictable to the adversary. JAMMY is decentralized, as sensor nodes determine the next slot utilization pattern in a distributed and autonomous way. Results from performance analysis of the proposed solution show that JAMMY introduces negligible overhead yet allows multiple nodes to join the network, in a limited number of superframes.

This article presents Axiom, a DTLS-based approach to efficiently secure multicast group communication among IoT-constrained devices. Axiom provides an adaptation of the DTLS record layer, relies on key material commonly shared among the group members, and does not require one to perform any DTLS handshake. We made a proof-of-concept implementation of Axiom based on the tinyDTLS library for the Contiki OS and used it to experimentally evaluate performance of our approach on real IoT hardware. Results show that Axiom is affordable on resource-constrained platforms and performs significantly better than related alternative approaches.

This paper presents GREP, a highly scalable and efficient group rekeying protocol with the following merits. First, it rekeys the group with only two messages, introducing an overhead which is small, constant, and independent of the group size. Second, GREP considers collusion as a first-class attack. Third, GREP efficiently recovers the group from a collusion attack without recourse to a total member reinitialization. The recovery cost smoothly grows with the group size, and gradually increases with the attack severity. GREP achieves these results by organizing nodes into logical subgroups and exploiting the history of node joining events. This allows GREP to establish a total ordering among subgroups and among nodes in each subgroup, so making collusion recovery highly scalable and efficient. We evaluate performance from several standpoints, and show that GREP is deployable in large-scale networks of customary, even resource constrained, platforms.

Internet of Things (IoT) commonly identifies the upcoming network society where all connectable devices will be able to communicate with one another. In addition, IoT devices are supposed to be directly connected to the Internet, and many of them are likely to be battery powered. Hence, they are particularly vulnerable to Denial of Service (DoS) attacks specifically aimed at quickly draining battery and severely reducing device lifetime. In this paper, we propose SMACK, a security service which efficiently identifies invalid messages early after their reception, by checking a short and lightweight Message Authentication Code (MAC). So doing, further useless processing on invalid messages can be avoided, thus reducing the impact of DoS attacks and preserving battery life. In particular, we provide an adaptation of SMACK for the standard Constrained Application Protocol (CoAP). Finally, we experimentally evaluate SMACK performance through our prototype implementation for the resource constrained CC2538 platform. Our results show that SMACK is efficient and affordable in terms of memory requirements, computing time, and energy consumption.

DTLS is a standardized security protocol designed to provide end-to-end secure communication among two peers, and particularly considered for the emerging Internet of Things. In order to protect group communication, the IETF is currently working on a method to secure multicast messages through the same DTLS security services. However, such an approach relies on traditional DTLS sessions to protect unicast responses to multicast messages. This increases the amount of security material stored by group members and can have a relevant impact on network performance. In this paper we propose an extension to the IETF approach which allows to efficiently protect group responses by reusing the same group key material. Our proposal does not require to establish additional DTLS sessions, thus preserving high communication performance within the group and limiting storage overhead on group members. Furthermore, we discuss a suitable key management policy to provision and renew group key material.

Wireless Sensor Networks (WSNs) are frequently adopted in industrial applications. However, they are particularly prone to cyber-physical attacks. Since addressing all possible attacks is not viable, due to performance and economic reasons, it is vital to choose which attacks to address and which countermeasures to adopt. Hence, a quantitative analysis of attack impact is crucial to make an effective choice. In this paper, we present a simulative approach to attack impact analysis, and show that simulation results provide valuable insights on the attack severity. To fix ideas, we refer to a WSN monitoring pollutant emissions of a critical infrastructure. We analyze effects of cyber-physical attacks against the network, and rank them according to their impact severity. This supports designers in deciding which attacks to address and which countermeasures to select.

Wireless Sensor Networks (WSNs) are currently used in many application scenarios, including industrial applications and factory automation. In such scenarios, Time Division Multiple Access (TDMA) is typically used for data communication among sensor nodes. However, TDMA-based WSNs are particularly prone to Selective Jamming attack, a specific form of Denial of Service attack aimed at severely thwarting network reliability. In this paper, we present SAD-SJ, a self-adaptive and decentralized MAC-layer solution against selective jamming in TDMA-based WSNs. SAD-SJ does not need a central entity, requires sensor nodes to rely only on local information, and allows them to join and leave the network without hindering other nodes activity. We show that SAD-SJ introduces a limited overhead, in terms of computation, communication and energy consumption.

Group communication is a suitable and effective communication model for large-scale distributed systems. To be fully exploitable, group communication must be protected. This is normally achieved by providing members with a group key which is revoked and redistributed upon every member's joining (backward security) or leaving (forward security). Such a rekeying process must be efficient and highly scalable. In this paper, we present HISS, a highly scalable group rekeying scheme that efficiently rekeys the group into two broadcast rekeying messages. HISS features two novel contributions. First, it exhibits a rekeying cost which is constant and independent of the group size, thus being highly scalable with the number of users. At the same time, memory occupancy and computational overhead are affordable on customary platforms. Second, HISS considers collusion as a first-class attack and recovers the group in such a way that it does not require a total group recovery. Efficiency of collusion recovery gracefully decreases with the attack severity. We prove the correctness of HISS, analytically evaluate its performance and argue that it is deployable on customary platforms. Finally, we show that it is possible to practically contrast or even prevent collusion attacks by properly allocating users to subgroups.

Wireless Sensor Networks are vulnerable to quite a good deal of logical and physical security attacks. However, providing security countermeasures for every possible attack is practically unfeasible for cost and performance reasons. Thus, it is vital to properly rank security attacks in order to establish priorities and then select appropriate countermeasures. In this paper, we present ASF, an attack simulation framework that allows us to describe attacks and quantitatively evaluate their effects on the application and network behavior and performance. ASF helps users to evaluate the impact of an attack, a crucial step in the attacks ranking activity. Also, we present an early prototype of ASF built on top of the popular simulator Castalia. Finally, we show the capabilities of ASF by analysing four attacks against a realistic application scenario.