Guest Editorial: Special Issue on Frontiers in Trust Management

Information and Communication Technologies (ICT) are becoming increasingly important in the way we organize our lives, our workplaces and our societies. ICT allows people and organisations, that have never interacted with each other in the past, to initiate new and mutually beneficial businesses across the world. This means that personal and business information is increasingly being communicated across interpersonal, inter-business and international borders. Keeping this information safe and protecting the fragile IT infrastructure from criminals is a growing problem in most societies. Unfortunately, traditional security technologies based on a strong perimeter defence work poorly in an inter-connected world that obeys Metcalfe’s law which states that “the value of a network is proportional to the square of the number of connected users of the system”, i.e., where there is a strong incentive for interactions across the different borders. During the past decade, trust management has emerged as a promising solution to many challenges in networks and distributed systems as well as emerging problems in computer security and privacy. This special issue on “Frontiers in Trust Management” attempts to highlight some of the latest re- search addressing those challenges. It collects a series of papers on trust management issues that extends papers and ideas presented at the Fifth IFIP WG 11.11 International Conference on Trust Management or one of the affiliated workshops in Copenhagen, June 27 – July 1, 2011

An efficient PHR service system supporting fuzzy keyword search and fine-grained access control

Outsourcing of personal health record (PHR) has attracted considerable interest recently. It can not only bring much convenience to patients, it also allows efficient sharing of medical information among researchers. As the medical data in PHR is sensitive, it has to be encrypted before outsourcing. To achieve fine-grained access control over the encrypted PHR data becomes a challenging problem. In this paper, we provide an affirmative solution to this problem. We propose a novel PHR service system which supports efficient searching and fine-grained access control for PHR data in a hybrid cloud environment, where a private cloud is used to assist the user to interact with the public cloud for processing PHR data. In our proposed solution, we make use of attribute-based encryption (ABE) technique to obtain fine-grained access control for PHR data. In order to protect the privacy of PHR owners, our ABE is anonymous. That is, it can hide the access policy information in ciphertexts. Meanwhile, our solution can also allow efficient fuzzy search over PHR data, which can greatly improve the system usability. We also provide security analysis to show that the proposed solution is secure and privacy-preserving. The experimental results demonstrate the efficiency of the proposed scheme.Peer ReviewedPostprint (author's final draft

Efficient Multi-User Keyword Search over Encrypted Data in Cloud Computing

As cloud computing becomes prevalent, more and more sensitive information are being centralized into the cloud. For the protection of data privacy, sensitive data usually have to be encrypted before outsourcing, which makes effective data utilization a very challenging task. In this paper, we propose a new method to enable effective fuzzy keyword search in a multi-user system over encrypted cloud data while maintaining keyword privacy. In this new system, differential searching privileges are supported, which is achieved with the technique of attribute-based encryption. Edit distance is utilized to quantify keywords similarity and develop fuzzy keyword search technique, which achieve optimized storage and representation overheads. We further propose a symbol-based trie-traverse searching scheme to improve the search efficiency. Through rigorous security analysis, we show that our proposed solution is secure and privacy-preserving, while correctly realizing the goal of fuzzy keyword search with multiple users

Database Security System for Applying Sophisticated Access Control via Database Firewall Server

Database security, privacy, access control, database firewall, data break masking Recently, information leakage incidents have occurred due to database security vulnerabilities. The administrators in the traditional database access control methods grant simple permissions to users for accessing database objects. Even though they tried to apply more strict permissions in recent database systems, it was difficult to properly adopt sophisticated access control policies to commercial databases due to performance degradations. This paper proposes a database security system including a database firewall server as an enhanced database access control system which can efficiently enforce sophisticated security policies to provide database with confidentiality using a data masking technique for diverse conditions such as the date, time, SQL string, and table columns to database systems

Supporting Concurrency and Multiple Indexes in Private Access to Outsourced Data

Data outsourcing has recently emerged as a successful solution allowing individuals and organizations to delegate data and service management to external third parties. A major challenge in the data outsourcing scenario is how to guarantee proper privacy protection against the external server. Recent promising approaches rely on the organization of data in indexing structures that use encryption and the dynamic allocation of encrypted data to physical blocks for destroying the otherwise static relationship between data and the blocks in which they are stored. However, dynamic data allocation implies the need to re-write blocks at every read access, thus requesting exclusive locks that can affect concurrency. Also, these solutions only support search conditions on the values of the attribute used for building the indexing structure. In this paper, we present an approach that overcomes such limitations by extending the recently proposed shuffle index structure with support for concurrency and multiple indexes. Support for concurrency relies on the use of several differential versions of the data index that are periodically reconciled and applied to the main data structure. Support for multiple indexes relies on the definition of secondary shuffle indexes that are then combined with the primary index in a single data structure whose content and allocation is unintelligible to the server. We show how using such differential versions and combined index structure guarantees privacy, provides support for concurrent accesses and multiple search conditions, and considerably increases the performance of the system and the applicability of the proposed solution

Better Security for Queries on Encrypted Databases

Private database query (PDQ) processing has received much attention from the fields of both cryptography and databases. While previous approaches to design PDQ protocols exploit several cryptographic tools concurrently, recently the appearance of fully homomorphic encryption (FHE) schemes enables us to design PDQ protocols without the aid of additional tools. However, to the best of our knowledge, all currently existing FHE-based PDQ protocols focus on protecting only constants in query statements, together with the client\u27s data stored in the database server. In this paper, we provide a FHE-based PDQ protocol achieving better security, protecting query types as well as constants in query statements for conjunctive, disjunctive, and threshold queries with equality comparison. Our contributions are three-fold: First, we present a new security definition that reflects our enhanced security model which additionally protects query types in query statements. Second, we provide a new design for PDQ protocols using FHE schemes. To do this, we come up with a method to homomorphically evaluate our encrypted target queries on the encrypted database. Thereafter, we apply it to construct a protocol and show its security under our enhanced security definition in the semi-honest model. Finally, we provide proof-of-concept implementation results of our PDQ protocol. According to our rudimentary experiments, it takes 40 seconds to perform a query on 2352 elements consisting of 11 attributes of 40-bit using Brakerski-Gentry-Vaikuntanathan\u27s leveled FHE with SIMD techniques for 80-bit security, yielding an amortized rate of just 0.12 seconds per element

Selective and private access to outsourced data centers

The advancements in the Information Technology and the rapid diffusion of novel computing paradigms have accelerated the trend of moving data to the cloud. Public and private organizations are more often outsourcing their data centers to the cloud for economic and/or performance reasons, thus making data confidentiality an essential requirement. A basic technique for protecting data confidentiality relies on encryption: data are encrypted by the owner before their outsourcing. Encryption however complicates both the query evaluation and enforcement of access restrictions to outsourced data. In this chapter, we provide an overview of the issues and techniques related to the support of selective and private access to outsourced data in a scenario where the cloud provider is trusted for managing the data but not for reading their content. We therefore illustrate methods for enforcing access control and for efficiently and privately executing queries (at the server side) over encrypted data. We also show how the combined adoption of approaches supporting access control and for efficient query evaluation may cause novel privacy issues that need to be carefully handled