9896890
Secure and Efficient Key Management in Mobile Ad Hoc Networks
In mobile ad hoc networks, due to unreliable wireless media, host mobility and lack of infrastructure, providing secure communications is a big challenge in this unique network environment. Usually cryptography techniques are used for secure communications in wired and wireless networks. The asymmetric cryptography is widely used because of its versatileness (authentication, integrity, and confidentiality) and simplicity for key distribution. However, this approach relies on a centralized framework of public key infrastructure (PKI). The symmetric approach has computation efficiency, yet it suffers from potential attacks on key agreement or key distribution. In fact, any cryptographic means is ineffective if the key management is weak. Key management is a central aspect for security in mobile ad hoc networks. In mobile ad hoc networks, the computational load and complexity for key management is strongly subject to restriction of the node's available resources and the dynamic nature of network topology. In this paper, we propose a secure and efficient key management framework (SEKM) for mobile ad hoc networks. SEKM builds PKI by applying a secret sharing scheme and an underlying multicast server group. In SEKM, the server group creates a view of the certification authority (CA) and provides certificate update service for all nodes, including the servers themselves. A ticket scheme is introduced for efficient certificate service. In addition, an efficient server group updating scheme is proposed.
2254959
Local-Safety-Information-Based Broadcasting in Hypercube Multicomputers with Node and Link Faults
This paper presents a method to cope with fault-tolerant broadcasting in hypercube multicomputers with both node and link faults. The local safety concept is extended to faulty hypercubes with both node and link faults. The local-safety-based algorithm is used in a fully unsafe hypercube, where there is no safe node. A fully unsafe hypercube can be split into a set of maximal safe subcubes. We show that if these maximal safe subcubes meet certain requirements given in the paper, broadcasting can still be carried out successfully and in some case optimal broadcast is still possible. The method is extended to fault-tolerant routing and multicasting when the system contains both node and link faults.
7582647
On self-similarity and hamiltonicity of dual-cubes
The dual-cube is a newly proposed topology for interconnection networks, which uses low dimensional hypercubes as building blocks. The primary advantages of the dual-cube over the hypercube are that, with the same node degree n, the dual-cube contains 2/sup n-1/ times more nodes than the hypercube and, with the same amount of nodes, the dual-cube has approximately 50% less links than the hypercube. This paper was focused on the investigations of the structural self-similarity and the Hamiltonian property of the dual-cube. It was shown that a dual-cube can be recursively constructed from lower dimensional dual-cubes and, conversely, a dual-cube can be recursively decomposed into lower dimensional dual-cubes. It was also proved that all dual-cubes are Hamiltonian. There exist multiple Hamiltonian cycles on a dual-cube, among which, [(n-1)/2] cycles are edge-disjoint. It was illustrated that rings and linear arrays can be effectively emulated on dual-cubes. Some strategies for track sharing in efficient VLSI layout design were also discussed.
17371165
QoS Routing in Hypercube Multicomputers
In this paper, we present a coding method to capture QoS information in hypercube multicomputers. The coding method is based on a localized algorithm where each node interacts with its neighbors to gather QoS information. Specifically, each node maintains a QoS vector where the k-th element represents the guaranteed QoS performance to a destination that is k hops away. The localized algorithm exhibits desirable properties of self-stabilizing, self-optimizing, and self-healing. Simulation results show that this coding method provides a good approximation of the minimum QoS value to a k-hop destination and, at the same time, uses a relatively small number of packets to propagate a change in link state (QoS value) compared with the classical distributed Bellman-Ford method.
27746153
Broadcasting in Faulty Cube-Connected-Cycles with Minimum Recovery Time
We propose a broadcasting algorithm for a faulty Cube-Connected-Cycles multiprocessor. The broadcasting algorithm delivers a message to all the nodes non-redundantly using a binomial tree. The traffic generated because of the recovery is guaranteed to be minimum.
16257632
XYZ: a scalable, partially centralized lookup service for large-scale peer-to-peer systems
Peer-to-peer (P2P) systems are characterized by direct access between peer computers, rather than through a centralized server. File sharing is the dominant P2P application on the Internet, allowing users to easily contribute, search and obtain content. P2P systems can be categorized by the degrees of centralization. For fully centralized systems, the lookup service will not be available when the central directory server is down. For purely decentralized and unstructured systems, since there is no information about which nodes are likely to have the relevant files, searching essentially amounts to random search. This makes the lookup service unscalable and unpredictable. The objective of this paper is to design a partially centralized, scalable and self-organizing lookup service (XYZ) for wide area P2P systems. A clustering method is used to create the system backbone by connecting the cluster heads together and a color clustering method is adopted to create color overlays and minimize the searching space. Simulations and analysis are also provided. Extensions are proposed to achieve better performance
36178651
The vertex linear arboricity of distance graphs
A distance graph is a graph G(R,D) with the set of all points of the real line as vertex set and two vertices u,[email protected]?R are adjacent if and only if |u-v|@?D where the distance set D is a subset of the positive real numbers. Here, the vertex linear arboricity of G(R,D) is determined when D is an interval between 1 and @d. In particular, the vertex linear arboricity of integer distance graphs G(D) is discussed, too.
6832021
Multiresolution Image Registration Based on Kullback-Leibler Distance
This paper extends our prior work on multi-modal image registration based on the a priori knowledge of the joint intensity dis- tribution that we expect to obtain, and Kullback-Leibler distance. This expected joint distribution can be estimated from pre-aligned training images. Experimental results show that, as compared with the Mutual Information and Approximate Maximum Likelihood based registration methods, the new method has longer capture range at different image resolutions, which can lead to a more robust image registration method. Moreover, with a simple interpolation algorithm based on non-grid point random sampling, the proposed method can avoid interpolation artifacts at the low resolution registration. Finally, it is experimentally demon- strated that our method is applicable to a variety of imaging modalities.
13581814
All-optical network demonstrator program centered around a testbed for verifying and validating next generation optical networks
The all-optical network (AON) demonstrator program is centered around a long-term trial testbed for the validation and verification of key network building blocks, scalable architectures, control and management solutions for next generation wavelength division multiplexing networks. The AON testbed has already validated certain system level concepts in both physical (performance characterization) and upper layers (network management). Performance characterization of optical signals was used to develop real-time monitoring techniques of the key network parameters for detection, identification and localization of signal degradations. Upper layer proof of concepts verified network level management approaches and optimizations for large and challenging applications. A prototype of a network management system was developed for customer-managed networks.
204989501
On clique partitions of split graphs
Abstract Split graphs are graphs formed by taking a complete graph and an empty graph disjoint from it and some or all of the possible edges joining the two. We prove that the problem of deciding the clique partition number is NP-complete, even when restricted to the class of split graphs.
1297042
An Access Control Scheme for Partially Ordered Set Hierarchy with Provable Security
In a hierarchical structure, an entity has access to another if and only if the former is a superior of the later. The access control scheme for a hierarchy represented by a partially ordered set (poset) has been researched intensively in the past years. In this paper, we propose a new scheme that achieves the best performance of previous schemes and is provably secure under a comprehensive security model.