Yee Wei Law

Survey and benchmark of block ciphers for wireless sensor networks

Cryptographic algorithms play an important role in the security architecture of wireless sensor networks (WSNs). Choosing the most storage- and energy-efficient block cipher is essential, due to the facts that these networks are meant to operate without human intervention for a long period of time with little energy supply, and that available storage is scarce on these sensor nodes. However, to our knowledge, no systematic work has been done in this area so far. We construct an evaluation framework in which we first identify the candidates of block ciphers suitable for WSNs, based on existing literature and authoritative recommendations. For evaluating and assessing these candidates, we not only consider the security properties but also the storage- and energy-efficiency of the candidates. Finally, based on the evaluation results, we select the most suitable ciphers for WSNs, namely Skipjack, MISTY1, and Rijndael, depending on the combination of available memory and required security (energy efficiency being implicit). In terms of operation mode, we recommend Output Feedback Mode for pairwise links but Cipher Block Chaining for group communications.

KLEIN: a new family of lightweight block ciphers

Resource-efficient cryptographic primitives are essential for realizing both security and efficiency in embedded systems like RFID tags and sensor nodes. Among those primitives, lightweight block cipher plays a major role as a building block for security protocols. In this paper, we describe a new family of lightweight block ciphers named KLEIN, which is designed for resource-constrained devices such as wireless sensors and RFID tags. Compared to related proposals, KLEIN has advantage in the software performance on legacy sensor platforms, while its hardware implementation can be compact as well.

LKHW: a directed diffusion-based secure multicast scheme for wireless sensor networks

In this paper, we present a mechanism for securing group communications in Wireless Sensor Networks (WSN). First, we derive an extension of logical key hierarchy (LKH). Then we merge the extension with directed diffusion. The resulting protocol, LKHW, combines the advantages of both LKH and directed diffusion: robustness in routing, and security from the tried and tested concepts of secure multicast. In particular, LKHW enforces both backward and forward secrecy, while incurring an energy cost that scales roughly logarithmically with the group size. This is the first security protocol that leverages directed diffusion, and we show how directed diffusion can be extended to incorporate security in an efficient manner.

Energy-efficient link-layer jamming attacks against wireless sensor network MAC protocols

A typical wireless sensor node has little protection against radio jamming. The situation becomes worse if energy-efficient jamming can be achieved by exploiting knowledge of the data link layer. Encrypting the packets may help to prevent the jammer from taking actions based on the content of the packets, but the temporal arrangement of the packets induced by the nature of the protocol might unravel patterns that the jammer can take advantage of, even when the packets are encrypted. By looking at the packet interarrival times in three representative MAC protocols, S-MAC, LMAC, and B-MAC, we derive several jamming attacks that allow the jammer to jam S-MAC, LMAC, and B-MAC energy efficiently. The jamming attacks are based on realistic assumptions. The algorithms are described in detail and simulated. The effectiveness and efficiency of the attacks are examined. In addition, we validate our simulation model by comparing its results with measurements obtained from actual implementation on our sensor node prototypes. We show that it takes little effort to implement such effective jammers, making them a realistic threat. Careful analysis of other protocols belonging to the respective categories of S-MAC, LMAC, and B-MAC reveals that those protocols are, to some extent, also susceptible to our attacks. The result of this investigation provides new insights into the security considerations of MAC protocols.

Link-layer jamming attacks on S-MAC

We argue that among denial-of-service (DoS) attacks, link-layer jamming is a more attractive option to attackers than radio jamming is. By exploiting the semantics of the link-layer protocol (aka MAC protocol), an attacker can achieve better efficiency than blindly jamming the radio signals alone. In this paper, we investigate some jamming attacks on S-MAC, the level of effectiveness and efficiency the attacks can potentially achieve and a countermeasure that can be implemented against one of these attacks.

A cellular-centric service architecture for machine-to-machine (M2M) communications

A machine-to-machine (M2M) communications system is a large-scale network with diverse applications and a massive number of interconnected heterogeneous machines (e.g., sensors, vending machines and vehicles). Cellular wireless technologies will be a potential candidate for providing the last mile M2M connectivity. Thus, the Third Generation Partnership Project (3GPP) and IEEE 802.16p, have both specified an overall cellular M2M reference architecture. The European Telecommunications Standards Institute (ETSI), in contrast, has defined a service- oriented M2M architecture. This article reviews and compares the three architectures. As a result, the 3GPP and 802.16p M2M architectures, which are functionally equivalent, complement the ETSI one. Therefore, we propose to combine the ETSI and 3GPP architectures, yielding a cellular-centric M2M service architecture. Our proposed architecture advocates the use of M2M relay nodes as a data concentrator. The M2M relay implements a tunnel-based aggregation scheme which coalesces data from several machines destined to the same tunnel exit-point. The aggregation scheme is also employed at the M2M gateway and the cellular base station. Numerical results show a significant reduction in protocol overheads as compared to not using aggregation at the expense of packet delay. However, the delay rapidly decreases with increasing machine density.

How to Secure a Wireless Sensor Network

The security of wireless sensor networks (WSNs) is a complex issue. While security research of WSNs is progressing at a tremendous pace, and many security techniques have been proposed, no comprehensive framework has so far emerged that attempts to tie the bits and pieces together to ease the implementors adoption of the technologies. We answer the challenge by proposing a guidelines according to which WSN security can be implemented in practice.

A Formally Verified Decentralized Key Management Architecture for Wireless Sensor Networks

We present a decentralized key management architecture for wireless sensor networks, covering the aspects of key deployment, key refreshment and key establishment. Our architecture is based on a clear set of assumptions and guidelines. Balance between security and energy consumption is achieved by partitioning a system into two interoperable security realms: the supervised realm trades off simplicity and resources for higher security whereas in the unsupervised realm the vice versa is true. Key deployment uses minimal key storage while key refreshment is based on the well-studied scheme of Abdalla et al. The keying protocols involved use only symmetric cryptography and have all been verified with our constraint solving-based protocol verification tool CoProVe.

WAKE: Key management scheme for wide-area measurement systems in smart grid

A wide-area measurement system (WAMS) is a system that provides a time-synchronized view of electrical conditions over a large geographical area, thereby enhancing the situational awareness of the energy management system of a power grid. With this enhanced situational awareness, utilities would be able to react promptly to contingencies, and prevent large-scale blackouts. To secure WAMS communications, we propose WAMS key management (WAKE), a comprehensive key management scheme targeting a concrete set of security objectives derived from NISTs security impact level ratings. For security objectives involving unicast, WAKE employs industry- standard security protocols. For security objectives involving multicast, we show the scheme standardized by the IEC is inadequate, and identify multicast authentication as a requirement. We investigate two recent multicast authentication schemes designed for power grid communications: TV-HORS and tunable signing and verification (TSV), which supposedly improves on TV-HORS. We show that TSV is vulnerable, and propose a patched version of TSV called TSV+. Systematic comparison of TV-HORS and TSV+ shows that TV-HORS provides significantly more efficient signing and verification for the same security level at the expense of signature size. Consequently, TV-HORS is chosen as part of WAKE for multicast authentication.

Demand Response Architectures and Load Management Algorithms for Energy-Efficient Power Grids: A Survey

A power grid has four segments: generation, transmission, distribution and demand. Until now, utilities have been focusing on streamlining their generation, transmission and distribution operations for energy efficiency. While loads have traditionally been a passive part of a grid, with rapid advances in ICT, demand-side technologies now play an increasingly important role in the energy efficiency of power grids. This paper starts by introducing the key concepts of demand-side management and demand-side load management. Classical demand-side management defines six load shape objectives, of which peak clipping and load shifting are most widely applicable and most relevant to energy efficiency. At present, the predominant demand-side management activity is demand response (DR). This paper surveys DR architectures, which are ICT architectures for enabling DR programs as well as load management. This paper also surveys load management solutions for responding to DR programs, in the form of load reduction and load shifting algorithms. A taxonomy for group load shifting is proposed. Research challenges and opportunities are identified and linked to ambient intelligence, wireless sensor networks, nonintrusive load monitoring, virtual power plants, etc.