141 research outputs found
A General Definition of Network Communities and the Corresponding Detection Algorithm
Network structures, consisting of nodes and edges, have applications in
almost all subjects. A set of nodes is called a community if the nodes have
strong interrelations. Industries (including cell phone carriers and online
social media companies) need community structures to allocate network resources
and provide proper and accurate services. However, all the current detection
algorithms are motivated by the practical problems, whose applicabilities in
other fields are open to question. Thence, for a new community problem,
researchers need to derive algorithms ad hoc, which is arduous and even
unnecessary. In this paper, we represent a general procedure to find community
structures in practice. We mainly focus on two typical types of networks:
transmission networks and similarity networks. We reduce them to a unified
graph model, based on which we propose a general method to define and detect
communities. Readers can specialize our general algorithm to accommodate their
problems. In the end, we also give a demonstration to show how the algorithm
works
Data-centric Misbehavior Detection in VANETs
Detecting misbehavior (such as transmissions of false information) in
vehicular ad hoc networks (VANETs) is very important problem with wide range of
implications including safety related and congestion avoidance applications. We
discuss several limitations of existing misbehavior detection schemes (MDS)
designed for VANETs. Most MDS are concerned with detection of malicious nodes.
In most situations, vehicles would send wrong information because of selfish
reasons of their owners, e.g. for gaining access to a particular lane. Because
of this (\emph{rational behavior}), it is more important to detect false
information than to identify misbehaving nodes. We introduce the concept of
data-centric misbehavior detection and propose algorithms which detect false
alert messages and misbehaving nodes by observing their actions after sending
out the alert messages. With the data-centric MDS, each node can independently
decide whether an information received is correct or false. The decision is
based on the consistency of recent messages and new alert with reported and
estimated vehicle positions. No voting or majority decisions is needed, making
our MDS resilient to Sybil attacks. Instead of revoking all the secret
credentials of misbehaving nodes, as done in most schemes, we impose fines on
misbehaving nodes (administered by the certification authority), discouraging
them to act selfishly. This reduces the computation and communication costs
involved in revoking all the secret credentials of misbehaving nodes.Comment: 12 page
A Security Architecture for Data Aggregation and Access Control in Smart Grids
We propose an integrated architecture for smart grids, that supports data
aggregation and access control. Data can be aggregated by home area network,
building area network and neighboring area network in such a way that the
privacy of customers is protected. We use homomorphic encryption technique to
achieve this. The consumer data that is collected is sent to the substations
where it is monitored by remote terminal units (RTU). The proposed access
control mechanism gives selective access to consumer data stored in data
repositories and used by different smart grid users. Users can be maintenance
units, utility centers, pricing estimator units or analyzing and prediction
groups. We solve this problem of access control using cryptographic technique
of attribute-based encryption. RTUs and users have attributes and cryptographic
keys distributed by several key distribution centers (KDC). RTUs send data
encrypted under a set of attributes. Users can decrypt information provided
they have valid attributes. The access control scheme is distributed in nature
and does not rely on a single KDC to distribute keys. Bobba \emph{et al.}
\cite{BKAA09} proposed an access control scheme, which relies on a centralized
KDC and is thus prone to single-point failure. The other requirement is that
the KDC has to be online, during data transfer which is not required in our
scheme. Our access control scheme is collusion resistant, meaning that users
cannot collude and gain access to data, when they are not authorized to access.
We theoretically analyze our schemes and show that the computation overheads
are low enough to be carried out in smart grids. To the best of our knowledge,
ours is the first work on smart grids, which integrates these two important
security components (privacy preserving data aggregation and access control)
and presents an overall security architecture in smart grids.Comment: 12 Pages, 3 figure
Alocalized algorithm for bi-connectivity of connected mobilerobots
Teams of multiple mobile robots may communicate with each-other using a wireless ad-hoc network. Fault-tolerance in communication can be achieved by making the communication network bi-connected. We present the first localized protocol for constructing a fault-tolerant bi-connected robotic network topology from a connected network, in such a way that the total movement of robots is minimized. The proposed distributed algorithm uses p-hop neighbor information to identify critical head robots that can direct two neighbors to move toward each other and bi-connect their neighborhood. Simulation results show that the total distance of movement of robots decreases significantly (e.g. about 2.5 times for networks with density 10) with our localized algorithm when compared to the existing globalized one. Proposed localized algorithm does not guarantee bi-connectivity, may partition the network, and may even stop at connected but not bi-connected stage. However, our algorithm achieved 100% success on all networks with average degrees ≥10, and over 70% success on sparse networks with average degrees ≥
Beaconless position based routing with guaranteed delivery for wireless ad-hoc and sensor networks
Existing position-based routing algorithms, where packets are forwarded in the geographic direction of the destination, normally require that the forwarding node knows the positions of all neighbors in its transmission range. This information on direct neighbors is gained by observing beacon messages that each node sends out periodically. Several beaconless greedy routing schemes have been proposed recently. However, none of the existing beaconless schemes guarantee the delivery of packets. Moreover, they incur communication overhead by sending excessive control messages or by broadcasting data packets. In this paper, we describe how existing localized position based routing schemes that guarantee delivery can be made beaconless, while preserving the same routes. In our guaranteed delivery beaconless routing scheme, the next hop is selected through the use of control RTS/CTS messages and biased timeouts. In greedy mode, neighbor closest to destination responds first. In recovery mode, nodes closer to the source will select shorter timeouts, so that other neighbors, overhearing CTS packets, can eliminate their own CTS packets if they realize that their link to the source is not part of Gabriel graph. Nodes also cancel their packets after receiving data message sent by source to the selected neighbor. We analyze the behavior of our scheme on our simulation environment assuming ideal MAC, following GOAFR+ and GFG routing schemes. Our results demonstrate low communication overhead in addition to guaranteed delivery.1st IFIP International Conference on Ad-Hoc NetWorkingRed de Universidades con Carreras en Informática (RedUNCI
Beaconless position based routing with guaranteed delivery for wireless ad-hoc and sensor networks
Existing position-based routing algorithms, where packets are forwarded in the geographic direction of the destination, normally require that the forwarding node knows the positions of all neighbors in its transmission range. This information on direct neighbors is gained by observing beacon messages that each node sends out periodically. Several beaconless greedy routing schemes have been proposed recently. However, none of the existing beaconless schemes guarantee the delivery of packets. Moreover, they incur communication overhead by sending excessive control messages or by broadcasting data packets. In this paper, we describe how existing localized position based routing schemes that guarantee delivery can be made beaconless, while preserving the same routes. In our guaranteed delivery beaconless routing scheme, the next hop is selected through the use of control RTS/CTS messages and biased timeouts. In greedy mode, neighbor closest to destination responds first. In recovery mode, nodes closer to the source will select shorter timeouts, so that other neighbors, overhearing CTS packets, can eliminate their own CTS packets if they realize that their link to the source is not part of Gabriel graph. Nodes also cancel their packets after receiving data message sent by source to the selected neighbor. We analyze the behavior of our scheme on our simulation environment assuming ideal MAC, following GOAFR+ and GFG routing schemes. Our results demonstrate low communication overhead in addition to guaranteed delivery.1st IFIP International Conference on Ad-Hoc NetWorkingRed de Universidades con Carreras en Informática (RedUNCI
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