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Outsourcing of data is a very common scenario in the present-day world and quite often we need to outsource confidential data whose privacy is of utmost concern. Performing encryption before outsourcing the data is a simple solution to preserve privacy. Preferably a public-key encryption technique is used to encrypt the data. A demerit of encrypting data is that while requesting the data from the cloud we need to have some technique which supports search functionality on encrypted data. Without the searchable encryption technique, the cloud is forced to send the whole database, which is highly inefficient and impractical. To address this problem, we consider the email scenario, in which the sender of the email will encrypt email contents using receiver's public key; hence, only the receiver can decrypt email contents. We propose a scheme that will have encrypted emails stored on the cloud and have capabilities that support searching through the encrypted database. This enables the cloud to reply to a request with a more precise response without compromising any privacy in terms of email contents and also in terms of access patterns. We provide a solution for the email scenario in which we can tag or associate emails with some keywords, and during retrieval, the email owner can request all the emails associated with a particular keyword. Although attempts are seen in the literature to solve this issue they do not have the flexibility of dissociating keywords from an email. Keyword dissociation is essential to modify the association between keywords and emails to enable better filtering of emails. Our technique also supports the functionality of keyword dissociation. The solution allows single-database private information retrieval writing in an oblivious way with sublinear communication cost. We have theoretically proved the correctness and security of our technique. [ABSTRACT FROM AUTHOR]

Let us consider the following situation: $$t$$ entities (e.g., hospitals) hold different databases containing different records for the same type of confidential (e.g., medical) data. They want to deliver a protected version of this data to third parties (e.g., pharmaceutical researchers), preserving in some way both the utility and the privacy of the original data. This can be done by applying a statistical disclosure control (SDC) method. One possibility is that each entity protects its own database individually, but this strategy provides less utility and privacy than a collective strategy where the entities cooperate, by means of a distributed protocol, to produce a global protected dataset. In this paper, we investigate the problem of distributed protocols for SDC protection methods. We propose a simple, efficient and secure distributed protocol for the specific SDC method of rank shuffling. We run some experiments to evaluate the quality of this protocol and to compare the individual and collective strategies for solving the problem of protecting a distributed database. With respect to other distributed versions of SDC methods, the new protocol provides either more security or more efficiency, as we discuss through the paper. [ABSTRACT FROM AUTHOR]

This paper investigates insider threat in relational database systems. It discusses the problem of inferring unauthorized information by insiders and proposes methods to prevent such threats. The paper defines various types of dependencies as well as constraints on dependencies that may be used by insiders to infer unauthorized information. It introduces the constraint and dependency graph (CDG) that represents dependencies and constraints. In addition, CDG shows the paths that insiders can follow to acquire unauthorized knowledge. Moreover, the paper presents the knowledge graph (KG) that demonstrates the knowledgebase of an insider and the amount of information that the insider has about data items. To predict and prevent insider threat, the paper defines and uses the threat prediction graph (TPG). A TPG shows the threat prediction value (TPV) of each data item in insiders' KG, where TPV is used to raise an alert when an insider threat occurs. The paper provides solutions to prevent insider threat without limiting the availability of data items. Algorithms, theorems, proofs and experiments are provided to show the soundness, the completeness and the effectiveness of the proposed approaches. [ABSTRACT FROM AUTHOR]

Since the concept of private information retrieval (PIR) was first formalized by Chor et al., various constructions have been proposed with a common goal of reducing communication complexity. Unfortunately, none of them is suitable for practical settings mainly due to the prohibitively high cost for either communications or computations. The booming of the Internet and its applications, especially, the recent trend in outsourcing databases, fuels the research on practical PIR schemes. In this paper, we propose a hardware-assisted PIR scheme with a novel shuffle algorithm. Our PIR construction entails O( n) offline computation cost, and constant online operations and O(log n) communication cost, where n is the database size. [ABSTRACT FROM AUTHOR]

Information is considered to be the most valuable asset of any organization and hence, it should be securely maintained. However, rapid proliferation of the Internet and Web applications has increased the threat of information security breaches. Traditional database security mechanisms are often not sufficient to protect sensitive information against novel attacks. Intrusion detection systems (IDS) are used to detect any such intrusion, once traditional security mechanisms have been compromised. User-level profile is effective for database intrusion detection, but maintaining such profiles is not practical for an organization with a large number of users. Thus, an IDS needs to be flexible enough to choose a profile granularity according to the type of the organization. Further, only intra-transactional pattern matching for intrusion detection is not quite effective for detecting intrusion in a database. We propose an IDS that uses inter-transactional as well as intra-transactional features for intrusion detection. It supports selection of profile and transactional feature granularity as well. We use sequence alignment as a tool for comparing database access patterns of genuine users and intruders. [ABSTRACT FROM AUTHOR]

Even state of the art database protection mechanisms often fail to prevent occurrence of malicious attacks. Since in a database environment, the modifications made by one transaction may affect the execution of some of the later transactions, it leads to spreading of the damage caused by malicious (bad) transactions. Following traditional log-based recovery schemes, one can rollback (undo) the effect of all the transactions, both malicious as well as non-malicious. In such a scenario, even the unaffected transactions are also rolled back. In this paper, we propose a column dependency-based approach to identify the affected transactions which need to be compensated along with the malicious transactions. To ensure durability, committed non-malicious transactions are then re-executed in a manner that retains database consistency. We present a static recovery algorithm as well as an on-line version of the same and prove their correctness. A detailed performance evaluation of the proposed scheme with TPC-C benchmark suite is also presented. [ABSTRACT FROM AUTHOR]

Controlled query evaluation (CQE) preserves confidentiality in information systems at runtime. A confidentiality policy specifies the information a certain user is not allowed to know. At each query, a censor checks whether the answer would enable the user to learn any classified information. In that case, the answer is distorted, either by lying or by refusal. We introduce a framework in which CQE can be analyzed wrt. possibly incomplete logic databases. For each distortion method, lying and refusal, a class of confidentiality-preserving mechanisms is presented. Furthermore, we specify a third approach that combines lying and refusal and compensates the disadvantages of the respective uniform methods. The enforcement methods are compared to the existing methods for complete databases. [ABSTRACT FROM AUTHOR]

A set DB of data elements can be represented in terms of its complement set, known as a negative database. That is, all of the elements not in DB are represented, and DB itself is not explicitly stored. This method of representing data has certain properties that are relevant for privacy enhancing applications. The paper reviews the negative database ( NDB) representation scheme for storing a negative image compactly, and proposes using a collection of NDBs to represent a single DB, that is, one NDB is assigned for each record in DB. This method has the advantage of producing negative databases that are hard to reverse in practice, i.e., from which it is hard to obtain DB. This result is obtained by adapting a technique for generating hard-to-solve 3-SAT formulas. Finally we suggest potential avenues of application. [ABSTRACT FROM AUTHOR]

We examine the popular proof models for group key establishment of Bresson et al. (LNCS 2248: 290–309, 2001; Proceedings of the 8th ACM conference on computer and communications security (CCS-8), 2001) and point out missing security properties addressing malicious protocol participants. We show that established group key establishment schemes from CRYPTO 2003 and ASIACRYPT 2004 do not fully meet these new requirements. Next to giving a formal definition of these extended security properties, we prove a variant of the explored proposal from ASIACRYPT 2004 secure in this stricter sense. Our proof builds on the Computational Diffie Hellman (CDH) assumption and the random oracle model. [ABSTRACT FROM AUTHOR]

Presents the preface for the August 8, 2004 issue of "International Journal of Information Security."