Kemal Bicakci

Denial-of-Service attacks and countermeasures in IEEE 802.11 wireless networks

IEEE 802.11 access points deployed in shopping malls, university campuses, crowded streets, airports, and many other locations provide ubiquitous Internet access to millions of stations. However, these hot spots are vulnerable to Denial-of-Service (DoS) attacks due to the broadcast nature of wireless communication. It does not require specialized hardware or particularly high level of experience to render 802.11 networks inoperable through DoS attacks. Standard off-the-shelf equipment is sufficient for a malicious station to disrupt the service between access points and stations. In this paper we present a systematic survey of DoS attacks, which exploits MAC and physical layer vulnerabilities of 802.11 networks. Available countermeasures against DoS attacks are discussed and compared. Future research directions and open issues are also discussed.

A survey of visual sensor network platforms

Recent developments in low-cost CMOS cameras have created the opportunity of bringing imaging capabilities to sensor networks. Various visual sensor platforms have been developed with the aim of integrating visual data to wireless sensor applications. The objective of this article is to survey current visual sensor platforms according to in-network processing and compression/coding techniques together with their targeted applications. Characteristics of these platforms such as level of integration, data processing hardware, energy dissipation, radios and operating systems are also explored and discussed.

The Impact of Transmission Power Control Strategies on Lifetime of Wireless Sensor Networks

Transmission power control has paramount importance in the design of energy-efficient wireless sensor networks (WSNs). In this paper, we systematically explore the effects of various transmission power control strategies on WSN lifetime with an emphasis on discretization of power levels and strategies for transmission power assignment. We investigate the effects of the granularity of power levels on energy dissipation characteristics through a linear programming framework by modifying a well known and heavily utilized continuous transmission power model (HCB model). We also investigate various transmission power assignment strategies by using two sets of experimental data on Mica motes. A novel family of mathematical programming models are developed to analyze the performance of these strategies. Bandwidth requirements of the proposed transmission power assignment strategies are also investigated. Numerical analysis of our models are performed to characterize the effects of various design parameters and to comparethe relative performance of transmission power assignment strategies. Our results show that the granularity of discrete energy consumption has a profound impact on WSN lifetime, furthermore, more fine-grained control of transmission power (i.e., link level control) can extend network lifetime up to 20% in comparison to optimally-assigned network-level single transmission power.

The impact of one-time energy costs on network lifetime in wireless sensor networks

In this letter, we present a mixed binary linear programming framework to investigate the impact of one-time energy costs on the overall system lifetime in wireless sensor networks. We use public-key cryptography as our representative one-time initialization operation. We show that the effect of public-key cryptography on optimal routes selection depends on the ratio of electronics energy to amplifier energy. The simulation results also reveal that the impact of public key cryptography on the maximum achievable lifetime of a sensor network is not negligible and it does not steadily increase with the size of the network.

Infinite length hash chains and their applications

Hash chains are used extensively in various cryptography applications such as one-time passwords, server-supported signatures and micropayments. In this paper, we present a method, called infinite length hash chains to improve the flexibility of this chaining idea by using public-key techniques. One of its distinguishing features is that communication and computation overhead of restarting of the system is avoided For the owner of the chain it is possible to go in either way in the chain at any time without any restriction in the chain length, but others see no difference as the functionality it provides with respect to traditional hash chains. On the other hand the drawback here is the increased computation cost due to public-key operations. Part of our work would be considered as one additional step after traditional one-time passwords in the natural progression from fixed password schemes to challenge-response identification protocols.

Maximizing lifetime of event-unobservable wireless sensor networks

In wireless sensor networks (WSNs) contextual information such as the information regarding whether, when, and where the data is collected cannot be protected using only traditional measures (e.g., encryption). Contextual information can be protected against global eavesdroppers by periodic packet transmission combined with dummy traffic filtering at proxy nodes. In this paper, through a Linear Programming (LP) framework, we analyze lifetime limits of WSNs preserving event-unobservability with different proxy assignment methodologies. We show that to maximize the network lifetime data flow should pass through multiple proxies that are organized as a general directed graph rather than as a tree.

Prolonging network lifetime with multi-domain cooperation strategies in wireless sensor networks

Abstract In wireless sensor networks nodes forward the data they acquire from the environment towards the base station by relaying through multiple intermediate sensor nodes used as relays. If multiple sensor networks are deployed in close proximity then they can help each others’ data forwarding so that all parties involved in such cooperation benefit from this collaborative effort (i.e., energy consumption for packet relaying reduces and the lifetime of each network is prolonged). There are many parameters that affect the impact of cooperation on sensor network lifetime such as number of domains, node density, network area, propagation environment, network topology, and base station deployment. In this paper we investigate cooperation strategies for prolonging sensor network lifetime in multi-domain wireless sensor networks through a linear programming framework. While our model is detailed enough to capture the essence of the multi-domain cooperation we intentionally avoid implementation specific details. Hence, we use our framework to determine almost achievable performance benchmarks in idealized yet practical settings. Our results show that under certain conditions (sparse network deployment and harsh propagation environment) multi-domain cooperation can extend the wireless network lifetime more than an order of magnitude when compared to non-cooperating domains of wireless sensor networks.

Towards Usable Solutions to Graphical Password Hotspot Problem

Click based graphical passwords that use background images suffer from hot-spot problem. Previous graphical password schemes based on recognition of images do not have a sufficiently large password space suited for most Internet applications. In this paper, we propose two novel graphical password methods based on recognition of icons to solve the hotspot problem without decreasing the password space. The experiment we have conducted that compares the security and usability of proposed methods with earlier work (i.e. Passpoints) shows that hotspot problem can be eliminated if a small increase in password entrance and confirmation times is tolerable.

How to construct optimal one-time signatures

One-time signature (OTS) offer a viable alternative to public key-based digital signatures. OTS security is typically based only on the strength of the underlying one-way function and does not depend on the conjectured difficulty of some mathematical problem. Although many OTS methods have been proposed in the past, no solid foundation exists for judging their efficiency or optimality. This paper develops a methodology for evaluating OTS methods and presents optimal OTS techniques for a single OTS or a tree with many OTSs. These techniques can be used in a seesaw mode to obtain the desired tradeoff between various parameters such as the cost of signature generation and its subsequent verification.

Lifetime Bounds of Wireless Sensor Networks Preserving Perfect Sink Unobservability

In wireless sensor networks an attack to the base station (sink) can render the whole network useless. Hence, concealing the physical location of the sink may be necessary in certain circumstances. Previous studies addressing this challenging problem assume a weak adversary model. The problem has not been studied in the presence of an eavesdropper who has global knowledge for the entire network. Here, a naive solution is to employ fake sinks so that nodes send their data not only to the real sink but also to other locations. An alternative solution with less overhead could be provided when all nodes including base station equalize the values of their total incoming and outgoing flows as well as their energy expenditure. This way, no information about the sink location is revealed even when all communication within the network is monitored. In this paper, through a Linear Programming (LP) framework we analyze and compare lifetime limits of wireless sensor networks preserving sink location privacy with the aforementioned two approaches.