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Given the growing number of group applications in many existing and evolving domains recent attention has been focused on secure multicasting over the Internet. When such systems are required to manage large groups that undergo frequent fluctuations in group membership, the need for efficient encryption key management becomes critical. This paper presents a… (More)

Low dilation embeddings are used to compare similarities between star and pancake networks. The pancake network of dimension n, Pn, has n! nodes, one for each permutation, and an undirected edge between permutations (nodes) when some prefix reversal transforms one permutation into the other. The star network of dimension n, Sn, has n! nodes, one for each… (More)

There are numerous applications that require secure group communication. Much recent attention has been focused on secure multicasting over the Internet. When such systems are required to manage large groups which undergo frequent fluctuations in group membership, the need for efficient encryption key management becomes critical. This paper presents a… (More)

Applications in information security, data mining, e-commerce, information retrieval and network management require the analysis of large graphs in order to discover homogeneous groupings of rows and columns, called cross associations. We show that finding an optimal cross association is NP-complete. Furthermore, we give a heuristic algorithm with an O(n 4)… (More)

Secure multicast has a variety of applications in e-commerce, e-banking, command and control, video-on-demand, and other internet-based services. In this paper, we present algorithms to improve on the number of re-keying messages (overhead) needed to add and delete sets of users to a secure multicast group. We present upper and lower bounds on the number of… (More)

The pancake problem asks for the minimum number of prefix reversals sufficient for sorting any permutation of length n. We improve the upper bound for the pancake problem to

A technique for clustering data by common attribute values involves grouping rows and columns of a binary matrix to make the minimum number of submatrices all 1's. As binary matrices can be viewed as adjacency matrices of bipartite graphs, the problem is equivalent to partitioning a bipartite graph into the smallest number of complete bipartite sub-graphs… (More)

Block sorting is used in connection with optical character recognition (OCR). Recent work has focused on finding good strategies which perform well in practice. Block sorting is N P-hard and all of the previously known heuristics lack proof of any approximation ratio. We present here an approximation algorithm for the block sorting problem with… (More)