25,276 research outputs found

    A Random Structure for Optimum Cache Size Distributed hash table (DHT) Peer-to-Peer design

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    We propose a new and easily-realizable distributed hash table (DHT) peer-to-peer structure, incorporating a random caching strategy that allows for {\em polylogarithmic search time} while having only a {\em constant cache} size. We also show that a very large class of deterministic caching strategies, which covers almost all previously proposed DHT systems, can not achieve polylog search time with constant cache size. In general, the new scheme is the first known DHT structure with the following highly-desired properties: (a) Random caching strategy with constant cache size; (b) Average search time of O(log2(N))O(log^{2}(N)); (c) Guaranteed search time of O(log3(N))O(log^{3}(N)); (d) Truly local cache dynamics with constant overhead for node deletions and additions; (e) Self-organization from any initial network state towards the desired structure; and (f) Allows a seamless means for various trade-offs, e.g., search speed or anonymity at the expense of larger cache size.Comment: 13 pages, 2 figures, preprint versio

    A Diffie-Hellman based key management scheme for hierarchical access control

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    All organizations share data in a carefully managed fashion\ud by using access control mechanisms. We focus on enforcing access control by encrypting the data and managing the encryption keys. We make the realistic assumption that the structure of any organization is a hierarchy of security classes. Data from a certain security class can only be accessed by another security class, if it is higher or at the same level in the hierarchy. Otherwise access is denied. Our solution is based on the Die-Hellman key exchange protocol. We show, that the theoretical worst case performance of our solution is slightly better than that of all other existing solutions. We also show, that our performance in practical cases is linear in the size of the hierarchy, whereas the best results from the literature are quadratic

    ARIES WP3 ā€“ Needs and Requirements Analyses

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    Information and communication technologies have increasingly influenced and changed our daily life. They allow global connectivity and easy access to distributed applications and digital services over the Internet. This report analysis security requirements on trust establishment and trust evaluation based on two different use case scenarios: "Trusted Communication using COTS" and "Trust Establishment for Cross-organizational Crises Management". A systematic needs analysis is performed on both scenarios which haver resulted in a large and well documented set of requirements. This is the first step in a large effort to define a security architecture for the two use case scenarios.

    Concurrent Lexicalized Dependency Parsing: A Behavioral View on ParseTalk Events

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    The behavioral specification of an object-oriented grammar model is considered. The model is based on full lexicalization, head-orientation via valency constraints and dependency relations, inheritance as a means for non-redundant lexicon specification, and concurrency of computation. The computation model relies upon the actor paradigm, with concurrency entering through asynchronous message passing between actors. In particular, we here elaborate on principles of how the global behavior of a lexically distributed grammar and its corresponding parser can be specified in terms of event type networks and event networks, resp.Comment: 68kB, 5pages Postscrip

    A Logic for Constraint-based Security Protocol Analysis

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    We propose PS-LTL, a pure-past security linear temporal logic that allows the specification of a variety of authentication, secrecy and data freshness properties. Furthermore, we present a sound and complete decision procedure to establish the validity of security properties for symbolic execution traces, and show the integration with constraint-based analysis techniques
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