We incorporate a prewrite operation before a write operation in a mobile transaction to improve data availability. A prewrite operation does not update the state of a data object but only makes visible the future value that the data object will have after the final commit of the transaction. Once a transaction reads all the values and declares all the prewrites, it can pre-commit at mobile host (MH) (computer connected to unreliable mobile communication network). The remaining transaction’s execution (writes on database) is shifted to the mobile service station (MSS) (computer connected to the reliable fixed network). Writes on database consume time and resources and are therefore shifted to MSS and delayed. This reduces wireless network traffic congestion. Since the responsibility of expensive part of the transaction’s execution is shifted to the MSS, it also reduces the computing expenses at mobile host. A pre-committed transaction’s prewrite values are made visible both at mobile and at fixed database servers before the final commit of the transaction. Thus, it increases data availability during frequent disconnection common in mobile computing. Since a pre-committed transaction does not abort, no undo recovery needs to be performed in our model. A mobile host needs to cache only prewrite values of the data objects which take less memory, transmission time, energy and can be transmitted over low bandwidth. We have analyzed various possible schedules of running transactions concurrently both at mobile and fixed database servers. We have discussed the concurrency control algorithm for our transaction model and proved that the concurrent execution of our transaction processing model produces only serializable schedules. Our performance study shows that our model increases throughput and decreases transaction-abort-ratio in comparison to other lock based schemes. We have briefly discussed the recovery issues and implementation of our model.

Some level of trust must be established before any collaboration or interaction can take place. Since trust and privacy are closely intertwined, a mere possibility of a privacy violation reduces trust among interacting entities. This impedes sharing and dissemination of sensitive data. Affected interactions range from simple transactions to the most complex collaborations. We want to assist users in properly protecting their privacy in such interactions. We also wish to help users give up the minimum degree of privacy necessary to gain the required level of trust—the level demanded by user’s partner as a pre-condition for a collaboration. In this paper, we focus on mechanisms for privacy-preserving dissemination of sensitive data. We next consider briefly the issues of privacy metrics and trading privacy for trust. Our test application in the area of location-based routing and services illustrates how to use the proposed privacy-for-trust approaches.

Several protocols have been proposed to defend against wormholes in ad hoc networks by adopting positioning devices, synchronized clocks, or directional antennas. In this paper, we propose a mechanism, MDS-VOW, to detect wormholes in a sensor network. MDS-VOW rst reconstructs the layout of the sensors using multi-dimensional scaling. To compensate the distortions caused by distance measurement errors, a surface smoothing scheme is adopted. MDS-VOW then detects the wormhole by visualizing the anomalies introduced by the attack. The anomalies, which are caused by the fake connections through the wormhole, bend the reconstructed surface to pull the sensors that are faraway to each other. Through detecting the bending feature, the wormhole is located and the fake connections are identified. The contributions of MDS-VOW are: (1) it does not require the sensors to be equipped with special hardware, (2) it adopts and combines the techniques from social science, computer graphics, and scientific visualization to attack the problem in network security. We examine the accuracy of the proposed mechanism when the sensors are deployed in a circle area and one wormhole exists in the network. The results show that MDS-VOW has a low false alarm ratio when the distance measurement errors are not large.

Several protocols have been proposed to defend against wormholes in ad hoc networks by adopting positioning devices, synchronized clocks, or directional antennas. In this paper, we propose a mechanism, MDS-VOW, to detect wormholes in a sensor network. MDS-VOW rst reconstructs the layout of the sensors using multi-dimensional scaling. To compensate the distortions caused by distance measurement errors, a surface smoothing scheme is adopted. MDS-VOW then detects the wormhole by visualizing the anomalies introduced by the attack. The anomalies, which are caused by the fake connections through the wormhole, bend the reconstructed surface to pull the sensors that are faraway to each other. Through detecting the bending feature, the wormhole is located and the fake connections are identified. The contributions of MDS-VOW are: (1) it does not require the sensors to be equipped with special hardware, (2) it adopts and combines the techniques from social science, computer graphics, and scientific visualization to attack the problem in network security. We examine the accuracy of the proposed mechanism when the sensors are deployed in a circle area and one wormhole exists in the network. The results show that MDS-VOW has a low false alarm ratio when the distance measurement errors are not large.

This paper studies the performance of a multi-rate mobile ad hoc network (MANET) using an extended ns-2 simulator. A link adaptation algorithm is developed and tested. The multi-rate control algorithm is based on the channel access mechanism for IEEE 802.11 with modifications. Some realistic models for radio propagation, such as lognormal fading and Walfisch/Ikagami propagation model, are used. At transport and application layer, different kinds of data traffic, including constant bit rate, TCP, voice over IP, and video are tested. The effects due to position error and mobility are also examined. The simulation results show that link layer data rate control can greatly improve network performance. Components at different layers all contribute to the system performance of a MANET. It is also shown that multimedia data transmission over MANETs deserves future study.

Due to scarce resources, such as transmission power, storage space and communication bandwidth, current broadcast approaches for general ad hoc networks can not be applied to IEEE 802.15.4 based ad hoc networks (e.g., ZigBee networks). This paper proposes a forward node selection algorithm that significantly reduces broadcast redundancy. The algorithm exploits the hierarchical address space in ZigBee networks. Only one-hop neighbor information is needed:  a partial list of two-hop neighbors is derived at a node without exchanging messages between neighboring nodes. The complexity of the proposed algorithm is polynomial in terms of both computation time and memory space. The localized algorithm provides an optimal and feasible solution of selecting the minimum number of rebroadcast nodes in ZigBee networks, which is an NP-hard problem for general ad hoc networks. The proposed algorithm is extended to deal with packet loss during data transmission. A ZigBee rebroadcast algorithm is also proposed to further reduce the number of rebroadcast nodes and cover the whole network faster by assigning a non-random rebroadcast timer determined by the number of neighbors to be covered, distance and link quality. Simulations are conducted to evaluate the broadcast redundancy, coverage time, and coverage ratio.

In this paper, we report some experiments and observations to make browsing of images more adaptable using small devices. We highlight the usability of such an alternative in mobile e-commerce and bandwidthconstrained systems.

Under-Water Sensor Networking (UWSN) is a novel network paradigm that is being proposed to explore, monitor and protect the oceans. The unique characteristics of the aquatic environment, namely huge propagation delay, absence of GPS signaling, floating node mobility, and limited (acoustic) link capacity, are very different from those of ground sensor networks. Since underwater networks are mostly autonomous and very difficult to directly monitor by humans, a very important requirement is the built-in protection from automated malicious attacks. In this paper we show that the aquatic environment is particularly vulnerable to attacks and security must be integrated into the UWSN architecture to protect its localization, synchronization and packet delivery services.

In this paper, we describe group key management protocosl for hierarchical sensor networks where instead of using pre-deployed keys, each sensor node generates a partial key dynamically using a function. The function takes partial keys of its children as input. The design of the protocol is motivated by the fact that traditional cryptographic techniques are impractical in sensor networks because of high energy and computational overheads. The group key management protocol supports the establishment of two types of group keys; one for the sensor nodes within a group, and the other in a group of cluster heads. The protocol handles freshness of the group key dynamically, and eliminates the involvement of a trusted third party (TTP). We have experimentally evaluated the time and energy consumption in broadcasting partial keys and group key under two sensor routing protocols (Tiny-AODV and Tiny-Diffusion) by varying the number of nodes and key sizes. The performance study provides the optimum number of partial keys needed for computing the group key to balance the available security and power consumption. The experimental study also concludes that the energy consumption in SPIN [9] increases rapidly as the number of group members increases in comparison to our protocol.

Trust - “reliance on the integrity, ability, or character of a person or thing” - is pervasive in social systems. We constantly apply it in interactions between people, organizations, animals, and even artifacts. We use it instinctively and implicitly in closed and static systems, or consciously and explicitly in open or dynamic systems. An epitome for the former case is a small village, where everybody knows everybody, and the villagers instinctively use their knowledge or stereotypes to trust or distrust their neighbors. A big city exemplifies the latter case, where people use explicit rules of behavior in diverse trust relationships. We already use trust in computing systems extensively, although usually subconsciously. The challenge for exploiting trust in computing lies in extending the use of trust-based solutions, first to artificial entities such as software agents or subsystems, then to human users’ subconscious choices.

In a cellular network, if there are too many data users in a cell, data may suffer long delay, and system’s quality-of-service (QoS) will degrade. Some traditional schemes such as dynamic channel-allocation scheme (DCA) will assign more channels to hot (or overloaded) cells through a central control system (CC), and the throughput increase will be upper bounded by the number of new chan- nels assigned to the cell. In mobile-assisted data forwarding (MADF), we add an ad-hoc overlay to the fixed cellular infrastructure and special channels–called forwarding channels– are used to connect mobile units in a hot cell and its surrounding cold cells without going through the hot cell’s base station. Thus, mobile units in a hot cell can forward data to other cold cells to achieve load balancing. Most of the forwarding-channel management work in MADF is done by mobile units themselves in order to relieve the load from the CC. The traffic increase in a certain cell will not be upper bounded by the number of forwarding channels. It can be more if the users in hot cell are significantly far away from one another, and these users can use the same forwarding channels to forward data to different cold neighboring cells without interference. We find that, in a system using MADF, under a certain delay requirement, the throughput in a certain cell or for the whole network can be greatly improved.

A key inhibitor to effective distance education in Information Technology is providing a “hands on” laboratory experience that allows students to acquire the application and problem solving skills expected of IT graduates. While there are instances of universities developing and deploying remote labs where students are able to perform labs through the Internet using “virtual machines” and other technologies, many have found the complexity and time required to maintain labs problematic and therefore prohibitive. This paper analyzes current trends in remote lab design and explores a design that intends to increase utilization between courses, lower costs, ease management, and reduce the time needed to implement remote labs.

Educators who have been through accreditation are well aware of the need for outcomes-based learning and assessment. However, there are misunderstandings about what outcomes based assessment is, and how it can improve teaching and learning. We understand that accreditation requirements can be a reason for adopting outcomes-based assessment, but our real goal is to convey to our readers how outcomes-based assessment can provide meaningful and useful feedback to the instructor regarding student achievement, assessment, and the quality of the instruction.

The IT2005 model curriculum describes Information Assurance and Security as a pervasive theme that must be integrated throughout the IT curriculum.  The associated knowledge area provides a minimum set of outcomes associated with this important subject.  Implementing a knowledge area that is required across the entire curriculum is a significant challenge, since security has historically been given weak coverage in computing courses.  In this paper we introduce the approaches used in two IT programs for implementing the IT2005 requirement for IAS as a “pervasive theme”.  We also include a brief introduction to IT2005 and to the Information Assurance Education community.  It is our belief that any program that is preparing students to deploy computing technology in the current world environment should include security concerns in the curriculum.  We hope that our experience can help others achieve this important goal.

In this paper we present the context of the work of the Curriculum Committee on IT2005, the IT curriculum volume described in the Overview Draft document of the Joint Task Force for Computing Curriculum 2004. We also provide a brief introduction to the history and work of the Information Assurance Education community. These two perspectives provide the foundation for the main thrust of the paper, which is a description of the Information Assurance and Security (IAS) component of the IT2005 document. Finally, we end the paper with an example of how IAS is being implemented at BYU as a “pervasive theme” that is woven throughout the curriculum and conclude with some observations about the first year’s experience.