42847493
Fingerprinting Text in Logical Markup Languages
Information hiding is attracting an increasing attention from the research community. Most of this research has centered around hiding information, such as watermarks and fingerprints, in images or digital audio and video signals. Text has generally been treated as a black & white image with special properties. All of the current methods of hiding information in text are vulnerable to scanning followed by optical character recognition in order to reconstruct the text.Document distribution is increasingly relying on logical markup languages like HTML and XML, where the physical presentation of the text is determined by the user's browser. Embedding the watermark in the physical presentation of the document is therefore no longer practical. We argue that embedding syntactic or semantic fingerprints in text is the only viable way to fingerprint document in logical markup languages such as HTML or XML.In this paper, we propose a new semantic fingerprinting mechanism based on synonymsubstitution. This idea is developed into an operational system and results of preliminary experiments are reported.
18687186
Trading Privacy for Trust
Both privacy and trust relate to knowledge about an entity. However, there is an inherent conflict between trust and privacy: the more knowledge a first entity knows about a second entity, the more accurate should be the trustworthiness assessment; the more knowledge is known about this second entity, the less privacy is left to this entity. This conflict needs to be addressed because both trust and privacy are essential elements for a smart working world. The solution should allow the benefit of adjunct trust when entities interact without too much privacy loss. We propose to achieve the right trade-off between trust and privacy by ensuring minimal trade of privacy for the required trust. We demonstrate how transactions made under different pseudonyms can be linked and careful disclosure of such links fulfils this right trade-off.
34386518
Privacy Recovery with Disposable Email Addresses
Disposable e-mail address (DEA) services are a privacy recovery mechanism for the growing spam problem. However, this problem is clearly more complex than simply closing DEA; as the rolling e-mail address protocols (REAP) system demonstrates, recovery approaches must accommodate different normal states.
7607582
Trust enhanced ubiquitous payment without too much privacy loss
Computational models of trust have been proposed for use in ubicomp environments for deciding whether to allow customers to pay with an e-purse or not. In order to build trust in a customer, a means to link transactions using the same e-purse is required. Roughly, trust is a result of knowledge. As the number of transactions increases, the resulting increase in knowledge about the user of the e-purse threatens privacy due to global profiling. We present a scheme (and its prototype) that mitigates this loss of privacy without forbidding the use of trust for smoothing payment by giving the opportunity to the user to divide trust (i.e. transactions) according to context (e.g. location, user's current activity or subset of shops).
2275333
Risk probability estimating based on clustering
Ubiquitous computing environments are highly dynamic, with new unforeseen circumstances and constantly changing environments, which introduces new risks that cannot be assessed through traditional means of risk analysis. Mobile entities in a ubiquitous computing environment require the ability to perform an autonomous assessment of the risk incurred by a specific interaction with another entity in a given context. This assessment will allow a mobile entity to decide whether sufficient evidence exists to mitigate the risk and allow the interaction to proceed. Such evidence might include records of prior experiences, recommendations from a trusted entity or the reputation of the other entity. We propose a dynamic mechanism for estimating the risk probability of a certain interaction in a given environment using hybrid neural networks. We argue that traditional risk assessment models from the insurance industry do not directly apply to ubiquitous computing environments. Instead, we propose a dynamic mechanism for risk assessment, which is based on pattern matching, classification and prediction procedures. This mechanism uses an estimator of risk probability, which is based on the automatic clustering of defining features of the environment and the other entity, which helps avoid subjective judgments as much as possible.
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.
41676213
Queries on Change in an Extended Relational Model
A data model that allows for the storage of detailed change history in so-called backlog relations is described. Its extended relational algebra, in conjunction with the extended data structures, provides a powerful tool for the retrieval of patterns and exceptions in change history. An operator, Sigma , based on the notion of compact active domain is introduced. It groups data not in predefined groups but in groups that fit the data. This operator further expands the retrieval capabilities of the algebra. The expressive power of the algebra is demonstrated by examples, some of which show how patterns and exceptions in change history can be detected. Sample applications of this work are statistical and scientific databases, monitoring (of databases, manufacturing plants, power plants, etc.), CAD, and CASE. >
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.
2109697
On the Ontological Expressiveness of Temporal Extensions to the Entity-Relationship Model
It is widely recognized that temporal aspects of database schemas are prevalent, but also difficult to capture using the ER model. The database research community's response has been to develop temporally enhanced ER models. However, these models have not been subjected to systematic evaluation. In contrast, the evaluation of modeling methodologies for information systems development is a very active area of research in the information systems engineering community. Based on a framework from information systems engineering, this paper evaluates the ontological expressiveness of three different temporal enhancements to the ER model. The three temporal ER model extensions are well-documented, and together the models represent a substantial range of the design space for temporal ER extensions.
2791621
R-Tree Based Indexing of Now-Relative Bitemporal Data
The databases of a wide range of applications, e.g., in data warehousing, store multiple states of time-evolving data. These databases contain a substantial part of now-relative data: data that became valid at some past time and remains valid until the current time. More specifically, two temporal aspects of data are frequently of interest, namely valid time, when data is true, and transaction time, when data is current in the database, leading to bitemporal data. Only little work, based mostly on R-trees, has addressed the indexing of bitemporal data. No indices exist that contend well with now-relative data, which leads to temporal data regions that are continuous functions of time. The paper proposes two extended R -trees that permit the indexing of data regions that grow continuously over time, by also letting the internal bounding regions grow. Internal bounding regions may be triangular as well as rectangular. New heuristics for the algorithms that govern the index structure are provided. As a result, dead space and overlap, now also functions of time, are reduced. Performance studies indicate that the best extended index is typically 3‐5 times faster than the existing R-tree based indices.
1683294
Transaction Timestamping in (Temporal) Databases
Many database applications need accountability and trace-ability that necessitate retaining previous database states. For a transaction-time database supporting this, the choice of times used to timestamp database records, to establish when records are or were current, needs to be consistent with a committed transaction serialization order. Previous solutions have chosen timestamps at commit time, selecting a time that agrees with commit order. However, SQL standard databases can require an earlier choice because a statement within a transaction may request “current time.” Managing timestamps chosen before a serialization order is established is the challenging problem we solve here. By building on two-phase locking concurrency control, we can delay a transaction’s choice of a timestamp, reducing the chance that transactions may need to be aborted in order keep timestamps consistent with a serialization order. Also, while timestamps stored with records in a transaction-time database make it possible to directly identify write-write and write-read conflicts, handling read-write conflicts requires more. Our simple auxiliary structure conservatively detects read-write conflicts, and hence provides transaction timestamps that are consistent with a serialization order.