TY - THES A1 - Krentz, Konrad-Felix T1 - A Denial-of-Sleep-Resilient Medium Access Control Layer for IEEE 802.15.4 Networks T1 - Eine Denial-of-Sleep-Resiliente Mediumzugriffsschicht für IEEE-802.15.4-Netzwerke N2 - With the emergence of the Internet of things (IoT), plenty of battery-powered and energy-harvesting devices are being deployed to fulfill sensing and actuation tasks in a variety of application areas, such as smart homes, precision agriculture, smart cities, and industrial automation. In this context, a critical issue is that of denial-of-sleep attacks. Such attacks temporarily or permanently deprive battery-powered, energy-harvesting, or otherwise energy-constrained devices of entering energy-saving sleep modes, thereby draining their charge. At the very least, a successful denial-of-sleep attack causes a long outage of the victim device. Moreover, to put battery-powered devices back into operation, their batteries have to be replaced. This is tedious and may even be infeasible, e.g., if a battery-powered device is deployed at an inaccessible location. While the research community came up with numerous defenses against denial-of-sleep attacks, most present-day IoT protocols include no denial-of-sleep defenses at all, presumably due to a lack of awareness and unsolved integration problems. After all, despite there are many denial-of-sleep defenses, effective defenses against certain kinds of denial-of-sleep attacks are yet to be found. The overall contribution of this dissertation is to propose a denial-of-sleep-resilient medium access control (MAC) layer for IoT devices that communicate over IEEE 802.15.4 links. Internally, our MAC layer comprises two main components. The first main component is a denial-of-sleep-resilient protocol for establishing session keys among neighboring IEEE 802.15.4 nodes. The established session keys serve the dual purpose of implementing (i) basic wireless security and (ii) complementary denial-of-sleep defenses that belong to the second main component. The second main component is a denial-of-sleep-resilient MAC protocol. Notably, this MAC protocol not only incorporates novel denial-of-sleep defenses, but also state-of-the-art mechanisms for achieving low energy consumption, high throughput, and high delivery ratios. Altogether, our MAC layer resists, or at least greatly mitigates, all denial-of-sleep attacks against it we are aware of. Furthermore, our MAC layer is self-contained and thus can act as a drop-in replacement for IEEE 802.15.4-compliant MAC layers. In fact, we implemented our MAC layer in the Contiki-NG operating system, where it seamlessly integrates into an existing protocol stack. N2 - Mit dem Aufkommen des Internets der Dinge (IoT), werden immer mehr batteriebetriebene und energieerntende Geräte in diversen Anwendungsbereichen eingesetzt, etwa in der Heimautomatisierung, Präzisionslandwirtschaft, Industrieautomatisierung oder intelligenten Stadt. In diesem Kontext stellen sogenannte Denial-of-Sleep-Angriffe eine immer kritischer werdende Bedrohung dar. Solche Angriffe halten batteriebetriebene, energieerntende oder anderweitig energiebeschränkte Geräte zeitweise oder chronisch ab, in energiesparende Schlafmodi überzugehen. Erfolgreiche Denial-of-Sleep-Angriffe führen zumindest zu einer langen Ausfallzeit der betroffenen Geräte. Um betroffene batteriebetriebene Geräte wieder in Betrieb zu nehmen, müssen zudem deren Batterien gewechselt werden. Dies ist mühsam oder eventuell sogar unmöglich, z.B. wenn solche Geräte an unzugänglichen Orten installiert sind. Obwohl die Forschungsgemeinschaft bereits viele Denial-of-Sleep-Abwehrmechanismen vorgeschlagen hat, besitzen die meisten aktuellen IoT-Protokolle überhaupt keine Denial-of-Sleep-Abwehrmechanismen. Dies kann zum einen daran liegen, dass man des Problems noch nicht gewahr ist, aber zum anderen auch daran, dass viele Integrationsfragen bislang ungeklärt sind. Des Weiteren existieren bisher sowieso noch keine effektiven Abwehrmechanismen gegen bestimmte Denial-of-Sleep-Angriffe. Der Hauptbeitrag dieser Dissertation ist die Entwicklung einer Denial-of-Sleep-resilienten Mediumzugriffsschicht für IoT-Geräte, die via IEEE-802.15.4-Funkverbindungen kommunizieren. Die entwickelte Mediumzugriffsschicht besitzt zwei Hauptkomponenten. Die erste Hauptkomponente ist ein Denial-of-Sleep-resilientes Protokoll zur Etablierung von Sitzungsschlüsseln zwischen benachbarten IEEE-802.15.4-Knoten. Diese Sitzungsschlüssel dienen einerseits der grundlegenden Absicherung des Funkverkehrs und andererseits der Implementierung zusätzlicher Denial-of-Sleep-Abwehrmechanismen in der zweiten Hauptkomponente. Die zweite Hauptkomponente ist ein Denial-of-Sleep-resilientes Mediumzugriffsprotokoll. Bemerkenswert an diesem Mediumzugriffsprotokoll ist, dass es nicht nur neuartige Denial-of-Sleep-Abwehrmechanismen enthält, sondern auch dem Stand der Technik entsprechende Mechanismen zur Verringerung des Energieverbrauchs, zur Steigerung des Durchsatzes sowie zur Erhöhung der Zuverlässigkeit. Zusammenfassend widersteht bzw. mildert unsere Denial-of-Sleep-resiliente Mediumzugriffsschicht alle uns bekannten Denial-of-Sleep-Angriffe, die gegen sie gefahren werden können. Außerdem kann unsere Denial-of-Sleep-resiliente Mediumzugriffsschicht ohne Weiteres an Stelle von IEEE-802.15.4-konformen Mediumzugriffsschichten eingesetzt werden. Dies zeigen wir durch die nahtlose Integration unserer Mediumzugriffsschicht in den Netzwerk-Stack des Betriebssystems Contiki-NG. KW - medium access control KW - denial of sleep KW - internet of things KW - Mediumzugriffskontrolle KW - Schlafentzugsangriffe KW - Internet der Dinge Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439301 ER - TY - GEN A1 - Seidel, Felix A1 - Krentz, Konrad-Felix A1 - Meinel, Christoph T1 - Deep En-Route Filtering of Constrained Application Protocol (CoAP) Messages on 6LoWPAN Border Routers T2 - 2019 IEEE 5th World Forum on Internet of Things (WF-IoT) N2 - Devices on the Internet of Things (IoT) are usually battery-powered and have limited resources. Hence, energy-efficient and lightweight protocols were designed for IoT devices, such as the popular Constrained Application Protocol (CoAP). Yet, CoAP itself does not include any defenses against denial-of-sleep attacks, which are attacks that aim at depriving victim devices of entering low-power sleep modes. For example, a denial-of-sleep attack against an IoT device that runs a CoAP server is to send plenty of CoAP messages to it, thereby forcing the IoT device to expend energy for receiving and processing these CoAP messages. All current security solutions for CoAP, namely Datagram Transport Layer Security (DTLS), IPsec, and OSCORE, fail to prevent such attacks. To fill this gap, Seitz et al. proposed a method for filtering out inauthentic and replayed CoAP messages "en-route" on 6LoWPAN border routers. In this paper, we expand on Seitz et al.'s proposal in two ways. First, we revise Seitz et al.'s software architecture so that 6LoWPAN border routers can not only check the authenticity and freshness of CoAP messages, but can also perform a wide range of further checks. Second, we propose a couple of such further checks, which, as compared to Seitz et al.'s original checks, more reliably protect IoT devices that run CoAP servers from remote denial-of-sleep attacks, as well as from remote exploits. We prototyped our solution and successfully tested its compatibility with Contiki-NG's CoAP implementation. Y1 - 2019 SN - 978-1-5386-4980-0 SN - 978-1-5386-4981-7 U6 - https://doi.org/10.1109/WF-IoT.2019.8767262 SP - 201 EP - 206 PB - Institute of Electrical and Electronics Engineers CY - New York ER - TY - JOUR A1 - Krentz, Konrad-Felix A1 - Meinel, Christoph T1 - Denial-of-sleep defenses for IEEE 802.15.4 coordinated sampled listening (CSL) JF - Computer Networks N2 - Coordinated sampled listening (CSL) is a standardized medium access control protocol for IEEE 80215.4 networks. Unfortunately, CSL comes without any protection against so-called denial-of-sleep attacks. Such attacks deprive energy-constrained devices of entering low-power sleep modes, thereby draining their charge. Repercussions of denial-of-sleep attacks include long outages, violated quality-of-service guarantees, and reduced customer satisfaction. However, while CSL has no built-in denial-of-sleep defenses, there already exist denial-of-sleep defenses for a predecessor of CSL, namely ContikiMAC. In this paper, we make two main contributions. First, motivated by the fact that CSL has many advantages over ContikiMAC, we tailor the existing denial-of-sleep defenses for ContikiMAC to CSL. Second, we propose several security enhancements to these existing denial-of-sleep defenses. In effect, our denial-of-sleep defenses for CSL mitigate denial-of-sleep attacks significantly better, as well as protect against a larger range of denial-of-sleep attacks than the existing denial-of-sleep defenses for ContikiMAC. We show the soundness of our denial-of-sleep defenses for CSL both analytically, as well as empirically using a whole new implementation of CSL. (C) 2018 Elsevier B.V. All rights reserved. KW - Internet of things KW - Link layer security KW - MAC security KW - Denial of sleep Y1 - 2018 U6 - https://doi.org/10.1016/j.comnet.2018.10.021 SN - 1389-1286 SN - 1872-7069 VL - 148 SP - 60 EP - 71 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Bock, Benedikt A1 - Matysik, Jan-Tobias A1 - Krentz, Konrad-Felix A1 - Meinel, Christoph T1 - Link Layer Key Revocation and Rekeying for the Adaptive Key Establishment Scheme T2 - 2019 IEEE 5TH World Forum on internet of things (WF-IOT) N2 - While the IEEE 802.15.4 radio standard has many features that meet the requirements of Internet of things applications, IEEE 802.15.4 leaves the whole issue of key management unstandardized. To address this gap, Krentz et al. proposed the Adaptive Key Establishment Scheme (AKES), which establishes session keys for use in IEEE 802.15.4 security. Yet, AKES does not cover all aspects of key management. In particular, AKES comprises no means for key revocation and rekeying. Moreover, existing protocols for key revocation and rekeying seem limited in various ways. In this paper, we hence propose a key revocation and rekeying protocol, which is designed to overcome various limitations of current protocols for key revocation and rekeying. For example, our protocol seems unique in that it routes around IEEE 802.15.4 nodes whose keys are being revoked. We successfully implemented and evaluated our protocol using the Contiki-NG operating system and aiocoap. KW - IEEE 802.15.4 KW - key management KW - key establishment KW - key revocation KW - rekeying KW - link layer security KW - MAC security Y1 - 2019 SN - 978-1-5386-4980-0 U6 - https://doi.org/10.1109/WF-IoT.2019.8767211 SP - 374 EP - 379 PB - IEEE CY - New York ER - TY - GEN A1 - Krentz, Konrad-Felix A1 - Meinel, Christoph A1 - Graupner, Hendrik T1 - More Lightweight, yet Stronger 802.15.4 Security Through an Intra-layer Optimization T2 - Foundations and Practice of Security N2 - 802.15.4 security protects against the replay, injection, and eavesdropping of 802.15.4 frames. A core concept of 802.15.4 security is the use of frame counters for both nonce generation and anti-replay protection. While being functional, frame counters (i) cause an increased energy consumption as they incur a per-frame overhead of 4 bytes and (ii) only provide sequential freshness. The Last Bits (LB) optimization does reduce the per-frame overhead of frame counters, yet at the cost of an increased RAM consumption and occasional energy-and time-consuming resynchronization actions. Alternatively, the timeslotted channel hopping (TSCH) media access control (MAC) protocol of 802.15.4 avoids the drawbacks of frame counters by replacing them with timeslot indices, but findings of Yang et al. question the security of TSCH in general. In this paper, we assume the use of ContikiMAC, which is a popular asynchronous MAC protocol for 802.15.4 networks. Under this assumption, we propose an Intra-Layer Optimization for 802.15.4 Security (ILOS), which intertwines 802.15.4 security and ContikiMAC. In effect, ILOS reduces the security-related per-frame overhead even more than the LB optimization, as well as achieves strong freshness. Furthermore, unlike the LB optimization, ILOS neither incurs an increased RAM consumption nor requires resynchronization actions. Beyond that, ILOS integrates with and advances other security supplements to ContikiMAC. We implemented ILOS using OpenMotes and the Contiki operating system. Y1 - 2018 SN - 978-3-319-75650-9 SN - 978-3-319-75649-3 U6 - https://doi.org/10.1007/978-3-319-75650-9_12 SN - 0302-9743 SN - 1611-3349 VL - 10723 SP - 173 EP - 188 PB - Springer CY - Cham ER -