JUCS - Journal of Universal Computer Science - Data
http://www.jucs.org/jucs_articles_by_category/E.
JUCS Topic E. - DataVerlag der Technischen Universität GrazUniversiti Malaysia Sarawak2011-07-28T11:21:46+02:00Cloud Warehousing
http://www.jucs.org/jucs_17_8/cloud_warehousing
Data warehouses integrate and aggregate data from various sources to support decision making within an enterprise. Usually, it is assumed that data are extracted from operational databases used by the enterprise. Cloud warehousing relaxes this view permitting data sources to be located anywhere on the world-wide web in a so-called "cloud", which is understood as a registry of services. Thus, we need a model of dataintensive web services, for which we adopt the view of the recently introduced model of abstract state services (AS2s). An AS2 combines a hidden database layer with an operation-equipped view layer, and thus provides an abstraction of web services that can be made available for use by other systems. In this paper we extend this model to an abstract model of clouds by means of an ontology for service description. The ontology can be specified using description logics, where the ABox contains the set of services, and the TBox can be queried to find suitable services. Consequently, AS2 composition can be used for cloud warehousing.Thalheim, Bernhard; Ma, Hui; Schewe, Klaus-Dieter; Wang, Qing2011-07-20T10:35:19+02:00cloud computingdata warehouseservice compositionservice ontologyservice-oriented computingtenantsCloud WarehousingThalheim, BernhardMa, HuiSchewe, Klaus-DieterWang, Qingcloud computing,data warehouse,service composition,service ontology,service-oriented computing,tenantsJUCS - Journal of Universal Computer Science Vol. 172011041183-1201Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaOn Compound Purposes and Compound Reasons for Enabling Privacy
http://www.jucs.org/jucs_17_3/on_compound_purposes_and
This paper puts forward a verification method for compound purposes and compound reasons to be used during purpose limitation.</P> <P>When it is absolutely necessary to collect privacy related information, it is essential that privacy enhancing technologies (PETs) protect access to data - in general accomplished by using the concept of purposes bound to data. Compound purposes and reasons are an enhancement of purposes used during purpose limitation and binding and are more expressive than purposes in their general form. Data users specify their access needs by making use of compound reasons which are defined in terms of (compound) purposes. Purposes are organised in a lattice with purposes near the greatest lower bound (GLB) considered weak (less specific) and purposes near the least upper bound (LUB) considered strong (most specific).</P> <P>Access is granted based on the verification of the statement of intent (from the data user) against the compound purpose bound to the data; however, because purposes are in a lattice, the data user is not limited to a statement of intent that matches the purposes bound to the data exactly - the statement can be a true reflection of their intent with the data. Hence, the verification of compound reasons against compound purposes cannot be accomplished by current published verification algorithms.</P> <P>Before presenting the verification method, compound purposes and reasons, as well as the structures used to represent them, and the operators that are used to define compounds is presented. Finally, some thoughts on implementation are provided.Olivier, Martin S.; Staden, Wynand van2011-04-24T11:15:18+02:00Compound PurposesDatabasesPrivacy Enhancing TechnologiesPurpose LatticesPurposesOn Compound Purposes and Compound Reasons for Enabling PrivacyOlivier, Martin S.Staden, Wynand vanCompound Purposes,Databases,Privacy Enhancing Technologies,Purpose Lattices,PurposesJUCS - Journal of Universal Computer Science Vol. 17201102426-450Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaWatermarking Techniques for Relational Databases: Survey, Classification and Comparison
http://www.jucs.org/jucs_16_21/watermarking_techniques_for_relational
Digital watermarking for relational databases emerged as a candidate solution to provide copyright protection, tamper detection, traitor tracing, maintaining integrity of relational data. Many watermarking techniques have been proposed in the literature to address these purposes. In this paper, we survey the current state-of-theart and we classify them according to their intent, the way they express the watermark, the cover type, the granularity level, and their verifiability.Cortesi, Agostino; Halder, Raju; Pal, Shantanu2011-03-18T16:20:43+01:00digital watermarkingfingerprintingrelational databasesWatermarking Techniques for Relational Databases: Survey, Classification and ComparisonCortesi, AgostinoHalder, RajuPal, Shantanudigital watermarking,fingerprinting,relational databasesJUCS - Journal of Universal Computer Science Vol. 162010123164-3190Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaXML Database Transformations
http://www.jucs.org/jucs_16_20/xml_database_transformations
Database transformations provide a unifying umbrella for queries and updates. In general, they can be characterised by five postulates, which constitute the database analogue of Gurevich's sequential ASM thesis. Among these postulates the background postulate supposedly captures the particularities of data models and schemata. For the characterisation of XML database transformations the natural first step is therefore to define the appropriate tree-based backgrounds, which draw on hereditarily finite trees, tree algebra operations, and extended document type definitions. This defines a computational model for XML database transformation using a variant of Abstract State Machines. Then the incorporation of weak monadic second-order logic provides an alternative computational model called XML machines. The main result is that these two computational models for XML database transformations are equivalent.Schewe, Klaus-Dieter; Wang, Qing2011-01-31T10:32:41+01:00Abstract State MachineMonadic Second-order LogicTree Algebracomputation backgrounddatabase transformationeXtensible Markup LanguageXML Database TransformationsSchewe, Klaus-DieterWang, QingAbstract State Machine,Monadic Second-order Logic,Tree Algebra,computation background,database transformation,eXtensible Markup LanguageJUCS - Journal of Universal Computer Science Vol. 162010113043-3072Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaA Geometrically Enhanced Conceptual Model and Query Language
http://www.jucs.org/jucs_16_20/a_geometrically_enhanced_conceptual
Motivated by our experiences with spatial modelling for the sustainable land use initiative we present a geometrically enhanced ER model (GERM), which preserves the key principles of entity-relationship modelling and at the same time introduces bulk constructors and geometric features. The model distinguishes between a syntactic level of types and an explicit internal level, in which types give rise to polyhedra that are defined by algebraic varieties. It further emphasises the stability of algebraic operations by means of a natural modelling algebra that extends the usual Boolean operations on point sets.Ma, Hui2011-01-31T10:32:32+01:00conceptual modelentity-relationship modelgeometric modelnatural modelling algebraquery languagespatial modelA Geometrically Enhanced Conceptual Model and Query LanguageMa, Huiconceptual model,entity-relationship model,geometric model,natural modelling algebra,query language,spatial modelJUCS - Journal of Universal Computer Science Vol. 162010112986-3015Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaLemmaGen: Multilingual Lemmatisation with Induced Ripple-Down Rules
http://www.jucs.org/jucs_16_9/lemma_gen_multilingual_lemmatisation
Lemmatisation is the process of finding the normalised forms of words appearing in text. It is a useful preprocessing step for a number of language engineering and text mining tasks, and especially important for languages with rich inflectional morphology. This paper presents a new lemmatisation system, LemmaGen, which was trained to generate accurate and efficient lemmatisers for twelve different languages. Its evaluation on the corresponding lexicons shows that LemmaGen outperforms the lemmatisers generated by two alternative approaches, RDR and CST, both in terms of accuracy and efficiency. To our knowledge, LemmaGen is the most efficient publicly available lemmatiser trained on large lexicons of multiple languages, whose learning engine can be retrained to effectively generate lemmatisers of other languages.Mozetič, Igor; Juršič, Matjaž; Lavrač, Nada; Erjavec, Tomaž2010-06-15T12:42:13+02:00lemmatisationnatural language processingripple-down rulesrule inductionLemmaGen: Multilingual Lemmatisation with Induced Ripple-Down RulesMozetič, IgorJuršič, MatjažLavrač, NadaErjavec, Tomažlemmatisation,natural language processing,ripple-down rules,rule inductionJUCS - Journal of Universal Computer Science Vol. 162010051190-1214Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaAlgebras and Update Strategies
http://www.jucs.org/jucs_16_5/algebras_and_update_strategies
The classical (Bancilhon-Spyratos) correspondence between view update translations and views with a constant complement reappears more generally as the correspondence between update strategies and meet complements in the order based setting of S. Hegner. We show that these two theories of database view updatability are linked by the notion of "lens" which is an algebra for a monad. We generalize lenses from the category of sets to consider them in categories with finite products, in particular the category of ordered sets.Johnson, Michael; Wood, Richard; Rosebrugh, Robert2010-07-04T18:32:44+02:00algebralensupdate strategyAlgebras and Update StrategiesJohnson, MichaelWood, RichardRosebrugh, Robertalgebra,lens,update strategyJUCS - Journal of Universal Computer Science Vol. 16201003729-748Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaGraph-Based Approach to the Edit Distance Cryptanalysis of Irregularly Clocked Linear Feedback Shift Registers
http://www.jucs.org/jucs_15_15/graph_based_approach_to
This paper proposes a speed-up of a known-plaintext attack on some stream ciphersbased on Linear Feedback Shift Registers (<I>LFSRs</I>). The algorithm consists of two basic steps: first, to guess the initial seed value of one of the <I>LFSRs</I>, and then to use the resulting binarysequence in order to deduce useful information about the cipher parameters. In particular, the proposed divide-and-conquer attack is based on a combination of graph-based techniques withedit distance concepts. While the original edit distance attack requires the exhaustive search over the set of all possible initial states of the involved <I>LFSR</I>, this work presents a new heuristic op-timization that avoids the evaluation of an important number of initial states through the identification of the most promising branches of the search graph. The strongest aspects of the proposalare the facts that the obtained results from the attack are absolutely deterministic, and that many inconsistent initial states of the target <I>LFSRs</I> are recognized and avoided during search.Fúster-Sabater, Amparo; Hernández-Goya, Candelaria; Caballero-Gil, Pino2010-11-25T11:07:15+01:00attacklinear feedback shift registersymmetric cryptographyGraph-Based Approach to the Edit Distance Cryptanalysis of Irregularly Clocked Linear Feedback Shift RegistersFúster-Sabater, AmparoHernández-Goya, CandelariaCaballero-Gil, Pinoattack,linear feedback shift register,symmetric cryptographyJUCS - Journal of Universal Computer Science Vol. 152009092981-2998Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaInformation Theoretically Secure Encryption with Almost Free Authentication
http://www.jucs.org/jucs_15_15/information_theoretically_secure_encryption
In cryptology, secure channels enable the exchange of messages in a confidential andauthenticated manner. The literature of cryptology is rich with proposals and analysis that address the secure communication over public (insecure) channels. In this work, we propose an informa-tion theoretically secure direction for the construction of secure channels. First, we propose a method of achieving unconditionally secure authentication with half the amount of key materialrequired by traditional unconditionally secure message authentication codes (MACs). Key reduction is achieved by utilizing the special structure of the authenticated encryption system. That is,authentication exploits the secrecy of the message to reduce the key material required for authentication. After the description of our method, since key material is the most important concernin unconditionally secure authentication, given the message is encrypted with a perfectly secret one-time pad cipher, we extend our method to achieve unconditionally secure authentication withalmost free key material. That is, we propose a method for unconditionally authenticating arbitrarily long messages with much shorter keys. Finally, we will show how the special structure ofthe authenticated encryption systems can be exploited to achieve provably secure authentication that is very efficient for the authentication of short messages.Alomair, Basel; Poovendran, Radha2010-11-25T11:07:05+01:00authenticationencryptionunconditional securityInformation Theoretically Secure Encryption with Almost Free AuthenticationAlomair, BaselPoovendran, Radhaauthentication,encryption,unconditional securityJUCS - Journal of Universal Computer Science Vol. 152009092937-2956Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaIdeal Homogeneous Access Structures Constructed from Graphs
http://www.jucs.org/jucs_15_14/ideal_homogeneous_access_structures
Starting from a new relation between graphs and secret sharing schemes introduced by Xiao, Liu and Zhang, we show a method to construct more general ideal homogeneous access structures. The method has some advantages: it efficiently gives an ideal homogeneous access structure for the desired rank, and some conditions can be imposed (such as forbidden or necessary subsets of players), even if the exact composition of the resulting access structure cannot be fully controlled. The number of homogeneous access structures that can be constructed in this way is quite limited; for example, we show that (<I>t</I>, <I>l</I>)-threshold access structures can be constructed from a graph only when <I>t</I> = 1, <I>t</I> = <I>l</I> - 1 or <I>t</I> = <I>l</I>.Herranz, Javier2010-11-15T11:10:43+01:00cryptographygraph connectivityideal secret sharingIdeal Homogeneous Access Structures Constructed from GraphsHerranz, Javiercryptography,graph connectivity,ideal secret sharingJUCS - Journal of Universal Computer Science Vol. 152009052881-2893Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaRough Classification - New Approach and Applications
http://www.jucs.org/jucs_15_13/rough_classification_new_approach
Rough classification has been known as the concept of Pawlak within the Rough Set Theory. In this paper the novel rough classification approach and its applications in e-learning systems and user interface management for recommendation processes will be presented.Nguyen, Ngoc Thanh2010-11-24T16:39:50+01:00E-learning systemsrough classificationuser managementRough Classification - New Approach and ApplicationsNguyen, Ngoc ThanhE-learning systems,rough classification,user managementJUCS - Journal of Universal Computer Science Vol. 152009072622-2628Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaUpdates, Schema Updates and Validation of XML Documents - Using Abstract State Machines with Automata-Defined States
http://www.jucs.org/jucs_15_10/updates_schema_updates_and
The exact validation of streaming XML documents can be realised by using visibly push-down automata (VPA) that are defined by Extended Document Type Definitions (EDTD). It is straightforward to represent such an automaton as an Abstract State Machine (ASM). In doing so we enable computations on abstract states that are defined by a certain class of automata, in this case VPAs. In this paper we elaborate on this approach by taking also updates of XML documents into account. In this way the ASM-approach combines vertical refinements, which first make states explicit and then instantiate by a specific EDTD, with horizontal refinements, which replace streaming XML documents by stored ones and then add updates. Furthermore, as the EDTD appears as part of the abstract state, updating it is another natural extension by horizontal refinement. In this way we obtain consistently integrated updates and schema updates for XML documents, which can even be extended to become fault-tolerant by taking at most k errors in the document into consideration. It further provides an example of ASM-based computation with automata-defined states.Thalheim, Bernhard; Schewe, Klaus-Dieter; Wang, Qing2010-11-24T12:32:06+01:00Abstract State MachinesValidationXMLUpdates, Schema Updates and Validation of XML Documents - Using Abstract State Machines with Automata-Defined StatesThalheim, BernhardSchewe, Klaus-DieterWang, QingAbstract State Machines,Validation,XMLJUCS - Journal of Universal Computer Science Vol. 152009052028-2057Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaCertificate-based Signatures Revisited
http://www.jucs.org/jucs_15_8/certificate_based_signatures_revisited
Certificate-based encryption was introduced in Eurocrypt'03 to solve the certificate management problem in public key encryption. Recently, this idea was extended to certificate-based signatures. Several new schemes and security models of certificate-based signatures have been proposed. In this paper, we first take a closer look at the certificate-based signature by comparing it with digital signatures in other popular public key systems. We introduce a new security model of certificate-based signature, which defines several new types of adversaries against certificate-based signatures, along with the security model of certificate-based signatures against them. The new model is clearer and more elaborated compared with other existing ones. We then investigate the relationship between certificate-based signatures and certificateless signatures, and propose a generic construction of certificate-based signatures. We prove that the generic construction is secure (in the random oracle model) against all types of adversaries defined in this paper, assuming the underlying certificateless signatures satisfying certain security notions. Based on our generic construction, we are able to construct new certificate-based signature schemes, which are more efficient in comparison with other schemes with similar security levels.Wu, Wei; Susilo, Willy; Huang, Xinyi; Mu, Yi2010-11-18T13:59:42+01:00certificate-based signaturescertificateless signaturesconcrete schemegeneric constructionsecurity modelCertificate-based Signatures RevisitedWu, WeiSusilo, WillyHuang, XinyiMu, Yicertificate-based signatures,certificateless signatures,concrete scheme,generic construction,security modelJUCS - Journal of Universal Computer Science Vol. 152009041659-1684Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, Austria<I>Light-Weight</I> Key Exchange with Different Passwords in the Standard Model
http://www.jucs.org/jucs_15_5/light_weight_key_exchange
In this paper, we consider password-based authenticated key exchange with different passwords, where the users only share a password with the trusted server but do not share between themselves. The server helps the users share a cryptographically secure session key by using their different passwords. We propose a light-weight password-based authenticated key exchange protocol with different passwords, i.e., it requires only 2 rounds and 4 modular exponentiations per user. The protocol provides forward secrecy, known-key secrecy, key secrecy against the curious server, and security against undetectable online dictionary attacks <I>without</I> random oracles.Lee, Dong Hoon; Jeong, Ik Rae; Kwon, Jeong Ok2010-11-18T10:28:07+01:00different passwordsforward secrecykey secrecypassword-based key exchange<I>Light-Weight</I> Key Exchange with Different Passwords in the Standard ModelLee, Dong HoonJeong, Ik RaeKwon, Jeong Okdifferent passwords,forward secrecy,key secrecy,password-based key exchangeJUCS - Journal of Universal Computer Science Vol. 152009031042-1064Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaSecurity Analysis of the Full-Round CHESS-64 Cipher Suitable for Pervasive Computing Environments
http://www.jucs.org/jucs_15_5/security_analysis_of_the
Wireless networks, telecommunications, and information technologies connected de-vices in pervasive computing environments require a high speed encryption for providing a high security and a privacy. The CHESS-64 based on various controlled operations is designed forsuch applications. In this paper, however, we show that CHESS-64 doesn't have a high security level, more precisely, we present two related-key differential attacks on CHESS-64. The first at-tack requires about 2<sup>44</sup> data and 2<sup>44</sup> time complexities (recovering 20 bits of the master key)while the second attack needs about 2<sup>39</sup> data and 2<sup>39</sup> time complexities (recovering 6 bits of themaster key). These works are the first known cryptanalytic results on CHESS-64 so far.Lee, Changhoon; Kim, Jongsung; Hong, Seokhie; Lee, Yang-Sun2010-11-18T10:27:56+01:00Block CipherCHESS-64Data-Dependent OperationData-Dependent PermutationDifferential CryptanalysisRelated-Key AttackSecurity Analysis of the Full-Round CHESS-64 Cipher Suitable for Pervasive Computing EnvironmentsLee, ChanghoonKim, JongsungHong, SeokhieLee, Yang-SunBlock Cipher,CHESS-64,Data-Dependent Operation,Data-Dependent Permutation,Differential Cryptanalysis,Related-Key AttackJUCS - Journal of Universal Computer Science Vol. 152009031007-1022Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaComplexity Analysis of Ontology Integration Methodologies:a Comparative Study
http://www.jucs.org/jucs_15_4/complexity_analysis_of_ontology
Most previous research on ontology integration has focused on similarity measure-ments between ontological <I>entities</I>, e.g., <I>lexicons</I>, <I>instances</I>, <I>schemas</I> and <I>taxonomies</I>, resulting in high computational costs of considering all possible pairs between two given ontologies. In this paper, we propose a novel approach to reducing computational complexity in ontology integration. Thereby, we address the <I>importance</I> and <I>types of concepts</I>, for priority matching anddirect matching between concepts, respectively. <I>Identity-based similarity</I> is computed, to avoid comparisons of all properties related to each concept, while matching between concepts. Theproblem of conflict in ontology integration has initially been explored on the <I>instance-level</I> and <I>concept-level</I>. This is useful to avoid many cases of mismatching.Jo, Geun Sik; Jung, Jason J.; Nguyen, Ngoc Thanh; Duong, Trong Hai2010-11-15T16:00:07+01:00conflictidentity-based similarityimportance conceptsontology integrationComplexity Analysis of Ontology Integration Methodologies:a Comparative StudyJo, Geun SikJung, Jason J.Nguyen, Ngoc ThanhDuong, Trong Haiconflict,identity-based similarity,importance concepts,ontology integrationJUCS - Journal of Universal Computer Science Vol. 15200902877-897Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaAdvances in Homomorphic Cryptosystems
http://www.jucs.org/jucs_15_3/advances_in_homomorphic_cryptosystems
During the last few years homomorphic encryption techniques have been studied extensively since they have become more and more important in many different cryptographic protocols such as voting protocols, lottery protocols, anonymity, privacy, and electronic auctions.</P> <P> This paper critically summarizes the current state-of-art of homomorphic cryptosystems. It recalls the basic ideas, discusses their parameters, performances and security issues. And, finally we present their capabilities in the future applications.Akinwande, Mufutau2010-11-15T15:16:24+01:00cryptosystemshomomorphic encryptionprobability encryptionAdvances in Homomorphic CryptosystemsAkinwande, Mufutaucryptosystems,homomorphic encryption,probability encryptionJUCS - Journal of Universal Computer Science Vol. 15200902506-522Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaLearner Course Recommendation in e-Learning Based on Swarm Intelligence
http://www.jucs.org/jucs_14_16/learner_course_recommendation_in
This paper analyses aspects about the recommendation process in distributed information systems. It extracts similarities and differences between recommendations in e-stores and the recommendations applied to an e-learning environment. It also explains the phenomena of self-organization and cooperative emergence in complex systems coupled with bio-inspired algorithms to improve knowledge discovery and association rules. Finally, the present recommendation is applied to e-learning by proposing recommendation by emergence in a Multi-Agent System architecture.Gil, Ana-Belén; García-Peñalvo, Francisco J.2009-08-04T21:26:54+02:00E-learningSwarm Intelligenceemergencemulti-agent systemrecommendationLearner Course Recommendation in e-Learning Based on Swarm IntelligenceGil, Ana-BelénGarcía-Peñalvo, Francisco J.E-learning,Swarm Intelligence,emergence,multi-agent system,recommendationJUCS - Journal of Universal Computer Science Vol. 142008082737-2755Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaNon-repudiation Mechanism of Agent-based Mobile Payment Systems: Perspectives on Wireless PKI
http://www.jucs.org/jucs_14_14/non_repudiation_mechanism_of
Non-repudiation of a mobile payment transaction ensures that when a buyer (B) sends some messages to a seller (S), neither B nor S can deny having participated in this transaction. An evidence of a transaction is generated by wireless PKI (WPKI) mechanism such that B and S cannot repudiate sending and receiving the purchase order respectively. Broker generates a mobile agent for B which carries encrypted purchase order to S. A trusted third party (TTP) acts as a lightweight notary for evidence generations. One advantage of this agent-based non-repudiation protocol is to reduce inconvenience for mobile clients such as connection time and search for suitable merchant servers, etc.; it provides necessary security mechanisms for fair mobile payment transactions.Ou, Chung-Ming; Ou, Chung-Ren2009-10-23T13:29:23+02:00WPKImobile agentnon-repudiationsecuritytrusted third partyNon-repudiation Mechanism of Agent-based Mobile Payment Systems: Perspectives on Wireless PKIOu, Chung-MingOu, Chung-RenWPKI,mobile agent,non-repudiation,security,trusted third partyJUCS - Journal of Universal Computer Science Vol. 142008072309-2328Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaSpatial Queries in Road Networks Based on PINE
http://www.jucs.org/jucs_14_4/spatial_queries_in_road
Over the last decade, due to the rapid developments in information technology (IT), a new breed of information systems has appeared such as geographic information systems that introduced new challenges for researchers, developers and users. One of its applications is the car navigation system, which allows drivers to receive navigation instructions without taking their eyes off the road. Using a Global Positioning System (GPS) in the car navigation system enables the driver to perform a wide range of queries, from locating the car position, to finding a route from a source to a destination, or dynamically selecting the best route in real time. Several types of spatial queries (e.g., nearest neighbour - NN, K nearest neighbours - KNN, continuous k nearest neighbours - CKNN, reverse nearest neighbour - RNN) have been proposed and studied in the context of spatial databases. With spatial network databases (SNDB), objects are restricted to move on pre-defined paths (e.g., roads) that are specified by an underlying network. In our previous work, we proposed a novel approach, termed Progressive Incremental Network Expansion (PINE), to efficiently support NN and KNN queries. In this work, we utilize our developed PINE system to efficiently support other spatial queries such as CKNN. The continuous K nearest neighbour (CKNN) query is an important type of query that finds continuously the K nearest objects to a query point on a given path. We focus on moving queries issued on stationary objects in Spatial Network Database (SNDB) (e.g., continuously report the five nearest gas stations while I am driving.) The result of this type of query is a set of intervals (defined by split points) and their corresponding KNNs. This means that the KNN of an object travelling on one interval of the path remains the same all through that interval, until it reaches a split point where its KNNs change. Existing methods for CKNN are based on Euclidean distances. In this paper we propose a new algorithm for answering CKNN in SNDB where the important measure for the shortest path is network distances rather than Euclidean distances. Our solution addresses a new type of query that is plausible to many applications where the answer to the query not only depends on the distances of the nearest neighbours, but also on the user or application need. By distinguishing between two types of split points, we reduce the number of computations to retrieve the continuous KNN of a moving object. We compared our algorithm with CKNN based on VN3 using IE (Intersection Examination). Our experiments show that our approach has better response time than approaches that are based on IE, and requires fewer shortest distance computations and KNN queries.Safar, Maytham2008-09-17T14:40:13+02:00PINEVoronoicontinuous nearest neighbornearest neighborroad networkSpatial Queries in Road Networks Based on PINESafar, MaythamPINE,Voronoi,continuous nearest neighbor,nearest neighbor,road networkJUCS - Journal of Universal Computer Science Vol. 14200804590-611Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaParallel Formulations of Scalar Multiplication on Koblitz Curves
http://www.jucs.org/jucs_14_3/parallel_formulations_of_scalar
We present an algorithm that by using the τ and τ<sup>-1</sup> Frobenius operators concurrently allows us to obtain a parallelized version of the classical τ-and-add scalar multiplicationalgorithm for Koblitz elliptic curves. Furthermore, we report suitable irreducible polynomials that lead to efficient implementations of both τ and τ<sup>-1</sup>, thus showing that our algorithm canbe effectively applied on all the NIST-recommended curves. We also present design details of software and hardware implementations of our procedure. In a two-processor workstation soft-ware implementation, we report experimental data showing that our parallel algorithm is able to achieve a speedup factor of almost 2 when compared with the standard sequential point multipli-cation. In our hardware implementation, the parallel version yields a more modest acceleration of 17% when compared with the traditional point multiplication algorithm. Although the focus ison Koblitz curves, analogous strategies are discussed for other curves, in particular for random curves over binary fields.Hankerson, Darrel; Rodríguez-Henríquez, Francisco; Ahmadi, Omran2008-09-17T13:43:20+02:00Koblitz curveselliptic curve cryptographyfast cryptographic algorithmsfinite field arithmeticParallel Formulations of Scalar Multiplication on Koblitz CurvesHankerson, DarrelRodríguez-Henríquez, FranciscoAhmadi, OmranKoblitz curves,elliptic curve cryptography,fast cryptographic algorithms,finite field arithmeticJUCS - Journal of Universal Computer Science Vol. 14200702481-504Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaCertificateless Public Key Encryption Secure against Malicious KGC Attacks in the Standard Model
http://www.jucs.org/jucs_14_3/certificateless_public_key_encryption
Recently, Au <I>et al.</I> [Au et al. 2007] pointed out a seemingly neglected security concern for certificateless public key encryption (CL-PKE) scheme, where a malicious key generation center (KGC) can compromise the confidentiality of the messages by embedding extra trapdoors in the system parameter. Although some schemes are secure against such an attack, they require random oracles to prove the security. In this paper, we first show that two existing CL-PKE schemes without random oracles are not secure against malicious KGC, we then propose the first CL-PKE scheme secure against malicious KGC attack, with proof in the standard model.Liu, Joseph K.; Chow, Sherman S.M.; Hwang, Yong Ho2008-09-17T13:43:16+02:00certificateless encryptionmalicious KGC attackstandard modelCertificateless Public Key Encryption Secure against Malicious KGC Attacks in the Standard ModelLiu, Joseph K.Chow, Sherman S.M.Hwang, Yong Hocertificateless encryption,malicious KGC attack,standard modelJUCS - Journal of Universal Computer Science Vol. 14200702463-480Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaBilateral Unknown Key-Share Attacks in Key Agreement Protocols
http://www.jucs.org/jucs_14_3/bilateral_unknown_key_share
Unknown Key-Share (UKS) resilience is a basic security attribute in authenticated key agreement protocols. In this paper we revisit the definitions of this attribute and the method of proving this attribute under the Bellare-Rogaway (BR) model in the literature. We propose a new type of UKS attack, which coerces two entities <I>A</I> and <I>B</I> into sharing a key with each other but in fact <I>A</I> thinks that he is sharing the key with another entity <I>C</I> and <I>B</I> thinks that he is sharing the key with another entity <I>D</I>, where <I>C</I> and <I>D</I> might or might not be the same entity. We call this attack a Bilateral Unknown Key-Share (BUKS) attack. We demonstrate that a few well-known authenticated key agreement protocols are vulnerable to this attack. We then explore a gap between the conventional BR-type proof and a BUKS adversary's behavior, and extend the BR model to cover the BUKS resilience attribute. At the end of the paper, we provide a general countermeasure and its security proof under the extended model and the assumption that a collision-resistance function exists.Chen, Liqun; Tang, Qiang2008-09-17T13:43:07+02:00authenticated key agreementbilateral unknown key-share resiliencethe Bellare-Rogaway modelunknown key-share resilienceBilateral Unknown Key-Share Attacks in Key Agreement ProtocolsChen, LiqunTang, Qiangauthenticated key agreement,bilateral unknown key-share resilience,the Bellare-Rogaway model,unknown key-share resilienceJUCS - Journal of Universal Computer Science Vol. 14200702416-440Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaParallel Key Exchange
http://www.jucs.org/jucs_14_3/parallel_key_exchange
In the paper we study parallel key exchange among multiple parties. The status of parallel key exchange can be depicted by a <I>key graph</I>. In a key graph, a vertex represents a party and an edge represents a relation of two parties who are to share a key.</P> <P>We first propose a security model for a key graph, which extends the Bellare-Rogaway model for two-party key exchange. Next, we clarify the relations among the various security notions of key exchange. Finally, we construct an efficient key exchange protocol for a key graph using the <I>randomness re-use</I> technique. Our protocol establishes the multiple keys corresponding to all edges of a key graph in a <I>single</I> session. The security of our protocol is proven in the standard model.Lee, Dong Hoon; Jeong, Ik Rae2008-09-17T13:43:03+02:00key exchangekey graphrandomness re-usesecurity notionsParallel Key ExchangeLee, Dong HoonJeong, Ik Raekey exchange,key graph,randomness re-use,security notionsJUCS - Journal of Universal Computer Science Vol. 14200702377-396Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaNew Results on NMAC/HMAC when Instantiated with Popular Hash Functions
http://www.jucs.org/jucs_14_3/new_results_on_nmac
Message Authentication Code (MAC) algorithms can provide cryptographically secure authentication services. One of the most popular algorithms in commercial applications is HMAC based on the hash functions MD5 or SHA-1. In the light of new collision search methods for members of the MD4 family including SHA-1, the security of HMAC based on these hash functions is reconsidered.</P> <P>We present a new method to recover both the inner- and the outer key used in HMAC when instantiated with a concrete hash function by observing text/MAC pairs. In addition to collisions, also other non-random properties of the hash function are used in this new attack. Among the examples of the proposed method, the first theoretical full key recovery attack on NMAC-MD5 is presented. Other examples are distinguishing, forgery and partial or full key recovery attacks on NMAC/HMAC-SHA-1 with a reduced number of steps (up to 62 out of 80). This information about the new, reduced security margin serves as an input to the selection of algorithms for authentication purposes.Rechberger, Christian; Rijmen, Vincent2008-09-17T13:42:59+02:00authenticationcryptographysecurityNew Results on NMAC/HMAC when Instantiated with Popular Hash FunctionsRechberger, ChristianRijmen, Vincentauthentication,cryptography,securityJUCS - Journal of Universal Computer Science Vol. 14200702347-376Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, AustriaEfficient k-out-of-n Oblivious Transfer Schemes
http://www.jucs.org/jucs_14_3/efficient_k_out_of
Oblivious transfer is an important cryptographic protocol in various security applications. For example, in on-line transactions, a <I>k</I>-out-of-<I>n</I> oblivious transfer scheme allows a buyer to <I>privately</I> choose <I>k</I> out of <I>n</I> digital goods from a merchant without learning information about other <I>n-k</I> goods. In this paper, we propose several efficient two-round <I>k</I>-out-of-<I>n</I> oblivious transfer schemes, in which the receiver <I>R</I> sends <I>O</I>(<I>k</I>) messages to the sender <I>S</I>, and <I>S</I> sends <I>O</I>(<I>n</I>) messages back to <I>R</I>. The schemes provide unconditional security for either sender or receiver. The computational security for the other side is based on the Decisional Diffie-Hellman (DDH) or Chosen-Target Computational Diffie-Hellman (CT-CDH) problems. Our schemes have the nice property of universal parameters, that is, each pair of <I>R</I> and <I>S</I> need not hold any secret before performing the protocol. The system parameters can be used by all senders and receivers without any trapdoor specification. In some cases, our OT<I><sup>k</sup><sub>n</sub></I> schemes are the most efficient ones in terms of the communication cost, either in rounds or the number of messages. Moreover, one of our schemes is extended to an adaptive oblivious transfer scheme. In that scheme, <I>S</I> sends <I>O</I>(<I>n</I>) messages to <I>R</I> in one round in the commitment phase. For each query of <I>R</I>, only <I>O</I>(1) messages are exchanged and <I>O</I>(1) operations are performed. The preliminary version of this paper was published at PKC '05 [Chu and Tzeng 2005].Chu, Cheng-Kang; Tzeng, Wen-Guey2008-09-17T13:42:41+02:00electronic commerceoblivious transferprivacy protectionEfficient k-out-of-n Oblivious Transfer SchemesChu, Cheng-KangTzeng, Wen-Gueyelectronic commerce,oblivious transfer,privacy protectionJUCS - Journal of Universal Computer Science Vol. 14200702397-415Verlag der Technischen Universität GrazUniversiti Malaysia SarawakGraz, Austria