Tuesday, August 25, 2009

IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 8, NO. 3, MARCH 2009

A FLEXIBLE PRIVACY-ENHANCED LOCATION-BASED SERVICES SYSTEM FRAMEWORK AND PRACTICE

Location-based services (LBSs) are becoming increasingly important to the success and attractiveness of next-generation wireless systems. However, a natural tension arises between the need for user privacy and the flexible use of location information. In this paper, we present a framework to support privacy-enhanced LBSs.

We classify the services according to several basic criteria, And we propose a hierarchical key distribution method to support these services. The main idea behind the system is to hierarchically encrypt location information under different keys, and distribute the appropriate keys only to group members with the necessary permission. Four methods are proposed to deliver hierarchical location information while maintaining privacy.

We propose a key tree-rebalancing algorithm to maintain the rekeying performance of the group key management. Furthermore, we present a practical LBS system implementation. Hierarchical location information coding offers flexible location information access which enables a rich set of LBSs.

Our load tests show such a system is highly practical with good efficiency and scalability.

Index Terms

Location-based services, location privacy, social networks, hierarchical key distribution.


IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 8, NO. 2,

FEBRUARY 2009

CONTENTION-AWARE PERFORMANCE ANALYSIS OF MOBILITY-ASSISTED ROUTING

A large body of work has theoretically analyzed the performance of mobility-assisted routing schemes for intermittently connected mobile networks. However, the vast majority of these prior studies have ignored wireless contention.

Recent papers have shown through simulations that ignoring contention leads to inaccurate and misleading results, even for sparse networks. In this paper, we analyze the performance of routing schemes under contention.

First, we introduce a mathematical framework to model contention. This framework can be used to analyze any routing scheme with any mobility and channel model. Then, we use this framework to compute the expected delays for different representative mobility-assisted routing schemes under random direction, random waypoint, and community-based mobility models.

Finally, we use these delay expressions to optimize the design of routing schemes while Demonstrating that designing and optimizing routing schemes using analytical expressions that ignore contention can lead to sub optimal or even erroneous behavior.

Index Terms

Delay-tolerant networks, wireless contention, performance analysis, mobility-assisted routing.


IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 17, NO. 1,

FEBRUARY 2009

NODE ISOLATION MODEL AND AGE-BASED NEIGHBOR SELECTION IN UNSTRUCTURED P2P NETWORKS

Previous analytical studies of unstructured P2P resilience have assumed exponential user lifetimes and only considered age-independent neighbor replacement. In this paper, we overcome these limitations by introducing a general node-isolation model for heavy-tailed user lifetimes and arbitrary neighbor-selection algorithms.

Using this model, we analyze two age-biased neighbor-selection strategies and show that they significantly improve the residual lifetimes of chosen users, which dramatically reduces the probability of user isolation and graph partitioning compared with uniform selection of neighbors.

In fact, the second strategy based on random walks on age-proportional graphs demonstrates that, for lifetimes with infinite variance, the system monotonically increases its resilience as its age and size grow.

Specifically, we show that the probability of isolation converges to zero as these two metrics tend to infinity. We finish the paper with simulations in finite-size graphs that demonstrate the effect of this result in practice.

Index Terms

Age-based selection, heavy-tailed lifetimes, node isolation, peer-to-peer networks, user churn.


Computer Science and Network Security, VOL.9 No.3, March 2009

A NOVEL APPROACH FOR COMPUTATION-EFFICIENT REKEYING FOR MULTICAST KEY DISTRIBUTION

An important problem for secure group communication is key distribution. Most of the centralized group key management schemes employ high rekeying cost.

Here we introduce a novel approach for computation efficient rekeying for multicast key distribution. This approach reduces the rekeying cost by employing a hybrid group key management scheme (involving both centralized and contributory key management schemes).

The group controller uses the MDS Codes, a class of error control codes, to distribute the multicast key dynamically. In order to avoid frequent rekeying as and when the user leaves, a novel approach is introduced where clients recompute the new group key with minimal computation.

This approach ensures forward secrecy as well as backward secrecy and significantly reduces the rekeying cost and communication cost. This scheme well suits wireless applications where portable devices require low computation.

Index Terms

Erasure decoding, Key Distribution, MDS Codes, Multicast.


IEEE TRANSACTIONS ON COMPUTERS, VOL. 58, NO. 7, JULY 2009

COLLUSIVE PIRACY PREVENTION IN P2P CONTENT DELIVERY NETWORKS

Collusive piracy is the main source of intellectual property violations within the boundary of a P2P network. Paid clients (colluders) may illegally share copyrighted content files with unpaid clients (pirates). Such online piracy has hindered the use of open P2P networks for commercial content delivery.

We propose a proactive content poisoning scheme to stop colluders and pirates from alleged copyright infringements in P2P file sharing. The basic idea is to detect pirates timely with identity-based signatures and time stamped tokens.

The scheme stops collusive piracy without hurting legitimate P2P clients by targeting poisoning on detected violators, exclusively. We developed a new peer authorization protocol (PAP) to distinguish pirates from legitimate clients. Detected pirates will receive poisoned chunks in their repeated attempts. Pirates are thus severely penalized with no chance to download successfully in tolerable time.

Based on simulation results, we find 99.9 percent prevention rate in Gnutella, KaZaA, and Freenet. We achieved 85- 98 percent prevention rate on eMule, eDonkey, Morpheus, etc. The scheme is shown less effective in protecting some poison-resilient networks like BitTorrent and Azureus. Our work opens up the low-cost P2P technology for copyrighted content delivery.

The advantage lies mainly in minimum delivery cost, higher content availability, and copyright compliance in exploring P2P network resources.

Index Terms

Peer-to-peer networks, content poisoning, copyright protection, network security.


OPPORTUNISTIC SCHEDULING WITH RELIABILITY GUARANTEES IN COGNITIVE RADIO NETWORKS - 2009

We develop opportunistic scheduling policies for cognitive radio networks that maximize the throughput utility of thesecondary (unlicensed) users subject to maximum collision constraints with the primary (licensed) users.

We consider a cognitive network with static primary users and potentially mobile secondary users.

We use the technique of Lyapunov Optimization to design an online flow control, scheduling, and resource allocation algorithm that meets the desired objectives and provides explicit performance guarantees.

Index Terms

Cognitive radio, queuing analysis, resource allocation, Lyapunov optimization.

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