10575596
Trust-based privacy preservation for peer-to-peer data sharing
Privacy preservation in a peer-to-peer (P2P) system tries to hide the association between the identity of a participant and the data that it is interested in. This paper proposes a trust-based privacy-preservation method for P2P data sharing. It adopts the trust relation between a peer and its collaborators (buddies). The buddy works as a proxy to send the request and acquire the data. This provides a shield under which the identity of the requester and the accessed data cannot be linked. A privacy measuring method is presented to evaluate the proposed mechanism. Dynamic trust assessment and the enhancement to supplier's privacy are discussed
1177051
Visualization assisted detection of sybil attacks in wireless networks
In wireless networks,the authenticity and uniqueness of node identities are essential to the fundamental operations such as routing, resource allocation, and intrusion detection. In this paper, we investigate Sybil attack, an attack in which a malicious node illegitimately acquires multiple identities and performs as these nodes simultaneously. We propose an effective approach to monitoring and detecting such attacks by integrating network security and visualization methods. The security component explores the time-varying network topology and its statistical and geometry information to detect the existence of Sybil attacks. The visualization component incorporates the detection results and provides an effective mechanism to illustrate abnormal topology patterns and locate fake identities. These two components are integrated into a practical system that takes advantage of both interactive visualization and intelligent security methods. Experimental studies are conducted to investigate the impacts of the network parameters such as node connectivity on the detection capability of the proposed mechanism.
270863
Study of distance vector routing protocols for mobile ad hoc networks
We investigate the performance issues of destination-sequenced distance vector (DSDV) and ad-hoc on-demand distance vector (AODV) routing protocols for mobile ad hoc networks. Four performance metrics are measured by varying the maximum speed of mobile hosts, the number of connections, and the network size. The correlation between network topology change and mobility is investigated by using linear regression analysis. The simulation results indicate that AODV outperforms DSDV in less stressful situations, while DSDV is more scalable with respect to the network size. It is observed that network congestion is the dominant reason for packet drop for both protocols. We propose a new routing protocol, congestion-aware distance vector (CADV), to address the congestion issues. CADV outperforms AODV in delivery ratio by about 5%, while introduces less protocol load. The result demonstrates that integrating congestion avoidance mechanisms with proactive routing protocols is a promising way to improve performance.
47778
Key distribution and update for secure inter-group multicast communication
Group communication has become an important component in wireless networks. In this paper, we focus on the environments in which multiple groups coexist in the system, and both intra and inter group multicast traffic must be protected by secret keys. We propose a mechanism that integrates polynomials with flat tables to achieve personal key share distribution and efficient key refreshment during group changes. The proposed mechanism distributes keys via true broadcast. The contributions of the research include: (1) By switching from asymmetric algorithms to symmetric encryption methods, the proposed mechanism avoids heavy computation, and improves the processing efficiency of multicast traffic and the power usage at the wireless nodes. The group managers do not have to generate public-private key pairs when the group member changes. (2) It becomes more difficult for an attacker to impersonate another node since personal key shares are adopted. The additional storage overhead at the wireless nodes and the increased broadcast traffic during key refreshment are justified. In addition, we describe techniques to improve the robustness of the proposed mechanism under the complicated scenarios such as collusive attacks and batch group member changes.
1103015
Visualization of wormholes in sensor networks
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 first 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.
12276338
User-oriented reliability modeling for a Web system
We develop a user-oriented reliability model, a simple yet effective approach, to address huge amounts of Web contents, and more importantly tackle users' dynamic navigation behaviors for a Web system. The users' intrinsic capabilities and behaviors, unlike programs' common recurring behaviors, call for a new approach for modeling the reliability of an organization's Web system. Our approach differs in the modeling scope of the Web system and the means of modeling user behaviors. We exploit the idea of cyclomatic complexity to cover the maximum number of independent paths, which overcome the less likely repetitive user navigations, and still maintain the dynamic nature of Web surfing. The modeling process takes Web senders' access, error, and referrer information as inputs, and translates them into a flow graph. A transition tree is then derived from the flow graph, based on depth-first traversal and dynamic programming. Accordingly, the reliability of the Web system can be computed by excluding those unreliable paths. This model is further applied to prioritize the error removal sequence to assist in allocating resources and effort.
62579240
A Selective Rendering Method for Data Visualization
Author(s): Wang, Wencheng; Wu, En-Hua; Max, Nelson | Abstract: Selective visualization is a solution for visualizing data of large size and dimensionality. In this paper a new method is proposed for effectively rendering certain chosen parts among the full set of data in terms of a colour buffer, referred to as the virtual plane, for storing intermediate results. By this method, scientists may concentrate their attention on the contents of data in which they are interested. Besides, the method could be easily integrated with all the current direct volume rendering techniques, especially progressive refinement methods and selective methods.
12798864
BASS: approximate search on large string databases
In this paper, we study the problem on how to build an index structure for large string databases to efficiently support various types of string matching without the necessity of mapping the substrings to a numerical space (e.g., string B-tree and MRS-index) nor the restriction of in-memory practice (e.g., suffix tree and suffix array). Towards this goal, we propose a new indexing scheme, BASS-tree, to efficiently support general approximate substring match (in terms of certain symbol substitutions and misalignments) in sublinear time on a large string database. The key idea behind the design is that all positions in each string are grouped recursively into a fully balanced tree according to the similarities of the subsequent segments starting at those positions. Each node is labeled with a regular expression that describes the commonality of the substrings indexed through the subtree. Any search can then be properly directed to the portion in the database with a high potential of matching quickly. With the BASS-tree in place, wild card(s) in the query pattern can also be handled in a seamless way. In addition, search of a long pattern can be decomposed into a series of searches of short segments followed by a process to join the results. It has been demonstrated in our experiments that the potential performance improvement brought by BASS-tree is in an order of magnitude over alternative methods.
29035045
Genetic algorithms for determining fuzzy measures from data
A synthetic evaluation of a given object in terms of multiple factors that contribute to some feature of the object (quality, performance, etc.) may be regarded as a system with multiple inputs and one output. Traditionally, the output is expressed as the weighted average of the inputs. Unfortunately, this method is severely limited as it cannot capture any inherent relation among the factors involved. This limitation can be overcome by using the Choquet integral or the fuzzy integral with respect to a fuzzy measure that captures the relation among the factors. The crux of this method is to determine the right fuzzy measure. In this paper, we describe an efficient genetic algorithm for constructing a suitable fuzzy measure from relevant input-output data. This algorithm has a broad applicability in various problem areas, such as decision making, cluster analysis, pattern recognition, image and speech processing, and expert systems.
12623712
A transparent rate adaptation algorithm for streaming video over the Internet
The lack of end-to-end quality of service support in the current Internet has caused significant difficulties to ensuring playback continuity in video streaming applications. This study addresses this challenge by investigating a new adaptation algorithm to adjust the bit-rate of video data in response to the network bandwidth available to improve playback continuity. Unlike previous works, the proposed algorithm is transparent to the video client, requires no parameter tuning, and yet can outperform existing algorithms. This paper presents this algorithm, evaluates and compares its performance with the best algorithm currently available using extensive trace-driven simulations.