14098973
CryptoCache: a secure sharable file cache for roaming users
Small mobile computers are now sufficiently powerful to run many applications, but storage capacity remains limited so working files cannot be cached or stored locally. Even if files can be stored locally, the mobile device is not powerful enough to act as server in collaborations with other users. Conventional distributed file systems cache everything locally or not at all; there is no possibility to cache files on nearby nodes.In this paper we present the design of a secure cache system called CryptoCache that allows roaming users to cache files on untrusted file hosting servers. The system allows flexible sharing of cached files among unauthenticated users, i.e. unlike most distributed file systems CryptoCache does not require a global authentication framework.Files are encrypted when they are transferred over the network and while stored on untrusted servers. The system uses public key cryptography, which allows roaming users to selectively grant read and write access to others by entrusting them with respectively the public key or the private key.
11578916
Adaptability in CORBA: the mobile proxy approach
Adaptability is one of the most important challenges in modern distributed systems. It may be defined as the ease with which a software application satisfies the different system constraints and the requirements of users and other applications. Adaptability is needed because distributed systems are inherently open, heterogeneous, and dynamic environments integrating a wide range of platforms, operating systems and applications from a number of different sources. We propose to use mobile proxies to provide adaptability in distributed applications integrated using the CORBA technology. Downloading stubs and skeletons at runtime allows the adaptation of either client or server interfaces as well as the protocol linking the two.
14855051
Mutual Suspicion in a Generic Object-Support System
We are currently facing the security paradox that applications must allow integration of information from various sources (like the web) and support global co-operation between users, i.e. there is a drive towards a stronger integration of information and services from weakly authenticated sources. In large networks like the Internet or enterprise wide intranets, without a common trusted computing base and no single source of authority in the system, a policy of mutual suspicion seems a prudent approach to co-operation.
16254824
Trust Propagation in Small Worlds
The possibility of a massive, networked infrastructure of diverse entities partaking in collaborative applications with each other increases more and more with the proliferation of mobile devices and the development of ad hoc networking technologies. In this context, traditional security measures do not scale well. We aim to develop trust-based security mechanisms using small world concepts to optimise formation and propagation of trust amongst entities in these vast networks. In this regard, we surmise that in a very large mobile ad hoc network, trust, risk, and recommendations can be propagated through relatively short paths connecting entities. Our work describes the design of trust-formation and risk-assessment systems, as well as that of an entity recognition scheme, within the context of the small world network topology.
14146996
Cryptographic access control in a distributed file system
Traditional access control mechanisms rely on a reference monitor to mediate access to protected resources. Reference monitors are inherently centralized and existing attempts to distribute the functionality of the reference monitor suffer from problems of scalability.Cryptographic access control is a new distributed access control paradigm designed for a global federation of information systems. It defines an implicit access control mechanism, which relies exclusively on cryptography to provide confidentiality and integrity of data managed by the system. It is particularly designed to operate in untrusted environments where the lack of global knowledge and control are defining characteristics.The proposed mechanism has been implemented in a distributed file system, which is presented in this paper along with a preliminary evaluation of the proposed mechanism.
8891155
The Claim Tool Kit for ad hoc recognition of peer entities
In ubiquitous/pervasive computing environments, it is envisaged that computing elements--entities--will start interacting in an ad hoc fashion. The peer-to-peer (p2p) paradigm is appealing for such types of interaction especially with JXTA, which supports the development of reusable p2p building blocks, which facilitate implementation on any smart device. However, the inability to rely on a centralised authentication infrastructure, the openness of the environment and the absence of an administrator (it is assumed to be too expensive to have a skilled administrator at hand due to the large number of peers) challenge the use of legacy authentication mechanisms.Supporting spontaneous interactions among previously unknown entities requires dynamic enrolment of strangers and unknown entities. Entity recognition (ER) is a process that is carried out each time an interaction happens between entities in order to dynamically recognise previously met entities.In this paper, we present the Claim Tool Kit (CTK), a Java-based implementation of ER: entities exchange messages, called Claims, and rely on their associated clues to evaluate the level of confidence in recognition.The CTK employs advanced features available with Java, such as JXTA and Java Cryptography and Security Architectures. We show that the CTK needs performance results on these features in order to increase the level of auto-configuration of the CTK. We describe how to obtain performance assessment for some of these new features. Finally, we explain how the CTK can be instrumented to take into account performance assessment. By analysing the evaluation results, the applicability of these advanced Java-based technologies for peer entity recognition is assessed.
1041340
Integrated Data Management for Mobile Services in the Real World
Market research companies predict a huge market for services to be delivered to mobile users. Services include route guidance, point-of-interest search, metering services such as road pricing and parking payment, traffic monitoring, etc. We believe that no single such service will be the killer service, but that suites of integrated services are called for. Such integrated services reuse integrated content obtained from multiple content providers. 
 
This paper describes concepts and techniques underlying the data management system deployed by a Danish mobile content integrator. While georeferencing of content is important, it is even more important to relate content to the transportation infrastructure. The data management system thus relies on several sophisticated, integrated representations of the infrastructure, each of which supports its own kind of use. The paper covers data modeling, querying, and update, as well as the applications using the system.
5224784
Nearest neighbor queries in road networks
With wireless communications and geo-positioning being widely available, it becomes possible to offer new e-services that provide mobile users with information about other mobile objects. This paper concerns active, ordered k-nearest neighbor queries for query and data objects that are moving in road networks. Such queries may be of use in many services.Specifically, we present an easily implementable data model that serves well as a foundation for such queries. We also present the design of a prototype system that implements the queries based on the data model. The algorithm used for the nearest neighbor search in the prototype is presented in detail. In addition, the paper reports on results from experiments with the prototype system.
16055581
Efficient evaluation of the valid-time natural join
Joins are arguably the most important relational operators. Poor implementations are tantamount to computing the Cartesian product of the input relations. In a temporal database, the problem is more acute for two reasons. First, conventional techniques are designed for the optimization of joins with equality predicates, rather than the inequality predicates prevalent in valid-time queries. Second, the presence of temporally-varying data dramatically increases the size of the database. These factors require new techniques to efficiently evaluate valid-time joins. The authors address this need for efficient join evaluation in databases supporting valid-time. A new temporal-join algorithm based on tuple partitioning is introduced. This algorithm avoids the quadratic cost of nested-loop evaluation methods; it also avoids sorting. Performance comparisons between the partition-based algorithm and other evaluation methods are provided. While the paper focuses on the important valid-time natural join, the techniques presented are also applicable to other valid-time joins.<<ETX>>
5130031
Temporal Data Management
A wide range of database applications manage time-varying information. Existing database technology currently provides little support for managing such data. The research area of temporal databases has made important contributions in characterizing the semantics of such information and in providing expressive and efficient means to model, store, and query temporal data. This paper introduces the reader to temporal data management, surveys stale-of-the-art solutions to challenging aspects of temporal data management, and points to research directions.
13198299
Research challenges in location-enabled m-services
Rapid, sustained advances in key computing hardware technologies combine to enable a new class of computing services that aim to meet the needs of mobile users. These ubiquitous and intelligent services adapt to each user's particular preferences and current circumstances, i.e., they are personalized. The services exploit data available front multiple sources, including data on past interactions with users, data accessible via the Internet, and data obtained from sensors. The user's geographical location is particularly central to these services. We outline some of the research challenges that aim to meet the computing of such services. In particular, focus is on update and query processing in the context of georeferenced data, where certain challenges related to the data representation, indexing and precomputation are described.