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We consider the problem of efficiently proving the integrity of data stored at untrusted servers. In the provable data possession (PDP) model, the client preprocesses the data and then sends it to an untrusted server for storage, while keeping a small amount of meta-data. The client later asks the server to prove that the stored data has not been tampered(More)
A directed graph is upward planar if it can be drawn in the plane such that every edge is a monotonically increasing curve in the vertical direction, and no two edges cross. An undirected graph is recti-linear planar if it can be drawn in the plane such that every edge is a horizontal or vertical segment, and no two edges cross. Testing upward planarity and(More)
We present a collection of new techniques for designing and analyzing eecient external-memory algorithms for graph problems and illustrate how these techniques can be applied to a wide variety of speciic problems. Our results include: Proximate-neighboring. We present a simple method for deriving external-memory lower bounds via reductions from a problem we(More)
We study the problem of providing privacy-preserving access to an outsourced honest-but-curious data repository for a group of trusted users. We show that such privacy-preserving data access is possible using a combination of probabilistic encryp-tion, which directly hides data values, and stateless oblivious RAM simulation, which hides the pattern of data(More)
We study a general version of the multicast authentica-tion problem where the underlying network, controlled by an adversary, may drop chosen packets, rearrange the order of the packets in an arbitrary way, and inject new packets into the transmitted stream. Prior work on the problem has focused on less general models, where random, rather than(More)
In the context of methodologies intended to confer robustness to geometric algorithms , we elaborate on the exact-computation paradigm and formalize the notion of degree of a geometric algorithm as a worst-case quantification of the precision (number of bits) to which arithmetic calculation have to be executed in order to guarantee topological correctness.(More)
This paper considers the problem of verifying the correctness of geometric structures. In particular, we design simple optimal checkers for convex polytopes in two and higher dimensions, and for various types of planar subdivisions, such as triangulations, Delaunay triangulations, and convex subdivisions. Their performance is analyzed also in terms of the(More)