21321848
Reasoning with advanced policy rules and its application
to access control
This paper presents a formal framework to represent and manage advanced policy rules, which incorporate the notions of provision and obligation. Provisions are those conditions that need to be satisfied or actions that must be performed by a user or an agent before a decision is rendered, while obligations are those conditions or actions that must be fulfilled by either the user or agent or by the system itself within a certain period of time after the decision. This paper proposes a specific formalism to express provisions and obligations within a policy and investigates a reasoning mechanism within this framework. A policy decision may be supported by more than one rule-based derivation, each associated with a potentially different set of provisions and obligations (called a global PO set). The reasoning mechanism can derive all the global PO sets for each specific policy decision and facilitates the selection of the best one based on numerical weights assigned to provisions and obligations as well as on semantic relationships among them. The formal results presented in the paper hold for many applications requiring the specification of policies, but this paper illustrates the use of the proposed policy framework in the security domain only.
31223197
Modeling Multilevel Entities Using Single Level Objects
An earlier paper by Jajodia and Kogan [5] introduced an approach for building multilevel secure object-oriented database systems based on a secure message filtering mechanism. Under this approach each object has a unique security level and, therefore, multilevel objects are not supported. In the present paper, we discuss an approach, based on composite objects, that allows multilevel entities to be represented in terms of single level objects. The main qualifying aspect of our approach is that the object interfaces can be provided to users as if multilevel objects were directly supported.
17632069
Secure Selective Exclusion in Ad Hoc Wireless Network
A wireless sensor network can be seen as a large number (hundreds of thousand) of small (a few cubic millimetres) devices, battery powered, with very limited hardware resources. Such a network has been studied specifically in the ad hoc model, where the sensors autonomously set up a network infrastructure. We propose here an extension to the current wireless ad hoc sensor network (WSN) model (in particular the base station model), by introducing a Supervisor which has very few interactions with the network, it is mobile in itself, it could have more powerful hardware and it is asynchronous with respect to the sensors. Nevertheless, the Supervisor has to interact with the sensor network, for example to invoke the command to exclude from the network a selected sensor. We believe such a model is particularly suitable for, but not limited to, military applications. We then propose a distributed, cooperative, parallel algorithm for this model that assures the following properties: it enforces both the secure exclusion of a selected compromised sensor from the network and the rekeying of the remaining sensors. It has an overall low overhead both in terms of computation and required transmitted messages. It is scalable, since the algorithm requires only limited, local knowledge of the network topology. Finally, it can be adopted, as an independent layer, to enforce secure exclusion in other models.
28618164
Bootstrapping a data mining intrusion detection system
The application of data mining techniques in intrusion detection has received a lot of attention lately. Most of the approaches require of a training phase based on the availability of labelled data, where the labels indicate whether the points correspond to normal events or attacks. Unfortunately, this labelled data is not readily available in practice. In this paper we present a novel method based in intersecting segments of unlabelled data and using the intersection as the base data for unsupervised learning (clustering). The clustering algorithm, along with a method to find outliers with respect to the base clusters form the basis for separation of unlabelled data into groups of points that are normal (attack-free) and points that correspond to attacks. We show that the technique is very sucessful in separating points of the data sets of the DARPA, Lincoln Labs evaluation of 1999.
33341357
Information Release Control: A Learning-Based Architecture
Modern information system applications involve collaboration in the form of information flow through organization boundaries. Indeed, organizations have vast amounts of information that is shared with other organizations and even the general public for various purposes. In addition to the standard network-level protections, systems usually use some access control mechanisms to protect data. However, access control systems are not designed to deal with deliberate and accidental release of information, to which the user has the authority to access but is not supposed to be released. Moreover, effective access control assumes a perfect categorization of information, which is increasingly difficult in a complex information system. Information release control is viewed as complementary to access control, and aims at restricting the outgoing information flow at the boundary of information systems. This paper presents a general architectural view of a release control system, and discusses the integration in the proposed architecture of a module for learning release control constraints. Continuous learning is applied to adjust the release control constraints in order to reduce both mistakenly released and mistakenly restricted documents. The paper describes in detail the process of learning keyword-based release control constraints.
6012377
Discovering calendar-based temporal association rules
A temporal association rule is an association rule that holds during specific time intervals. An example is that eggs and coffee are frequently sold together in morning hours. The paper studies temporal association rules during the time intervals specified by user-given calendar schemas. Generally, the use of calendar schemas makes the discovered temporal association rules easier to understand. An example of calendar schema is (year, month, day), which yields a set of calendar-based patterns of the form (d/sub 3/, d/sub 2/, d/sub 1/), where each d/sub i/ is either an integer or the symbol *. For example, (2000, *, 16) is such a pattern, which corresponds to the time intervals, each consisting of the 16th day of a month in year 2000. This paper defines two types of temporal association rules: precise-match association rules require that the association rule holds during every interval, and fuzzy-match ones require that the association rule holds during most of these intervals. The paper extends the well-known a priori algorithm, and also develops two optimization techniques to take advantage of the special properties of the calendar-based patterns. The experiments show that the algorithms and optimization techniques are effective.
120699
Enhancements to the Voting Algorithm
There are several consistency control algorithms for managing replicated files in the face of network partitioning due to site or communication link failures. In this paper, we consider the popular voting scheme along with three enhancements: voting with a primary site, dynamic voting, and dynamic voting with linearly ordered copiee. We develop a stochastic model which compares the file availabilities afforded by each of these schemes. We show that in this model dynamic voting with linearly ordered copies provides the greatest availability.
13277150
Mutual consistency in decentralized distributed systems
In this paper we set forth a simple and efficient algorithm for managing replicated data in a decentralized distributed system, which allows for inserts, deletes, updates, and synonyms and which achieves a high degree of availability in the face of node or communication failures. We focus on the approach developed recently by Fischer and Michael and exploit the knowledge of the semantics of the database operations.
13942242
A Scheme of Parallel Processing for MIMD Systems
This paper presents a recognition procedure for parallel tasks in the user program written in a conventional programming language. To establish our program model, it describes the parallelism of the program in tenns of a process flow graph in which the relationships among processes are of predecessors and successors. And finally it presents a parallel processing scheme which realizes automatically the recognition of parallel tasks and schedules these tasks for parallel execution.
45139817
Alternative methods for the reconstruction of trees from their traversals
It is well-known that given the inorder traversal of a binary tree's nodes, along with either one of its preorder or postorder traversals, the original binary tree can be reconstructed using a recursive algorithm. In this short note we provide a short, elegent, iterative solution to this classical problem.
24298643
Translation of entity-relationship diagrams into relational structures
Abstract An entity-relationship diagram (ERD) is considered to have two conceptual domains: its upper and lower conceptual domains. The semantic properties intrinsic in the upper conceptual domain were studied recently by Lien. In this paper, we discuss the properties inherent in the lower conceptual domain. We show that the latter contains a significant portion of the semantic information of an ERD and helps determine its data representation power. We develop the notions of fundamental functional dependencies (FDs) which can be readily recognized for the lower conceptual domain of an ERD, and regular ERDs which are ERDs such that all the FDs present among their attributes can be derived from their fundamental FDs. Then we give conditions under which a large number of ERDs are equivalent to their underlying relational structures.