8669872
Efficient and secure keys management for wireless mobile communications
This paper presents an efficient algorithm for the secure group key management of mobile users. The most promising protocols to deal with group key management are those based on logical key hierarchy (LKH). The LKH model reduces to logarithmic size the resources needed: computation time, message exchanged, and memory space. In the framework of the LKH model, we present a new protocol LKH++ that outperforms the other proposed solutions in the literature. Such performance improvements are obtained exploiting both the properties of one-way hash functions and the information that the users already share in the LKH model. In particular, when a user eviction occurs in LKH++, each remaining user autonomously constructs a new key along the path from the evicted user to the root as a function of a specific logical child key. Therefore, the center can carry on the re-keying phase by distributing only a subset of the new keys and by reducing the number of communications to the users. When a join occurs, a minimal information is broadcast, while most of the communications are unicast toward just the joining user. The proposed LKH++ protocol establishes a group communication of n users requiring to unicast ((n-1)logn)/2 keys, while standard algorithms require to deliver nlogn keys. Such a solution allows the users to form promptly a new group if the wireless ad hoc network should be reconfigured. Moreover, the proposed extension to deal with mass leave and mass join allows a considerable savings in the messages sent by the center, as well as in the computations required by both the center and the users. Finally, the LKH++ protocol enhances the reliability of the key management due to the reduced number of communications needed in the re-keying phase.
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.
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.
31726649
Scalable Group Rekeying for Secure Multicast: A Survey
Many group key management approaches have been recently proposed for providing scalable group rekeying to support secure communications for large and dynamic groups. We give an overview of these approaches and show the research trends. Finally, we discuss some new research directions on this subject.
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.
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.
21910023
On Universal and Representative Instances for Inconsistent Databases
18022126
Construction of Universal Instances for Loop-Free Network Databases Using a Join-Like Operation
In this paper, we give a polynomial-time method to construct effectively the unique universal instance, using as few nulls as possible, from any loop-free network database, via a "minimal information" extension of natural join. Our results can be seen as concretely and quickly implementing the universal relation view for databases which are not pairwise consistent.
14539530
The Problem of Equivalence for Entity-Relationship Diagrams
We investigate the question of when two entity-relationship diagrams (ERD's) should be considered equivalent, in the sense of representing the same information. This question is very important for a database design process which uses the ERD model, and can be interpreted in various ways. We give three natural and increasingly stricter criteria for developing concepts of equivalence for ERD's. We first give a notion of "domain data compatibility" which ensures that the ERD's in question represent the same universe of data in an aggregate sense. Then we define the set of functional dependencies which are naturally embedded in each ERD, and use it to develop a concept of "data dependency equivalence" which ensures that the ERD's satisfy the same constraints (functional dependencies) among the represented data. Finally, we give our strongest criterion, instance data equivalence, which requires the ERD's to have the same power to represent instances of data. We develop several alternate forms of this third notion, including some giving efficient tableaux tests for its occurrence. Indeed, for each type of equivalence, we give a polynomial-time algorithm to test for it.
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.