Fuzzy role-based access control

RBAC (Role-Based Access Control) is a widely used access control model, which reduces the maintenance cost of classical identity-based access control. However, despite the benefits of RBAC, there are environments in which RBAC can hardly be applied. We present FRBAC (Fuzzy Role-Based Access Control), a generalization of RBAC through fuzzy relations that extends the applicability of RBAC to environments where authorization-related information is vague. Moreover, FRBAC deals with environments where the actions that can be executed over the resources have a fractional meaning, as data lying in databases and risk-based access control

Mitigating Insider Threat in Relational Database Systems

The dissertation concentrates on addressing the factors and capabilities that enable insiders to violate systems security. It focuses on modeling the accumulative knowledge that insiders get throughout legal accesses, and it concentrates on analyzing the dependencies and constraints among data items and represents them using graph-based methods. The dissertation proposes new types of Knowledge Graphs (KGs) to represent insiders\u27 knowledgebases. Furthermore, it introduces the Neural Dependency and Inference Graph (NDIG) and Constraints and Dependencies Graph (CDG) to demonstrate the dependencies and constraints among data items. The dissertation discusses in detail how insiders use knowledgebases and dependencies and constraints to get unauthorized knowledge. It suggests new approaches to predict and prevent the aforementioned threat. The proposed models use KGs, NDIG and CDG in analyzing the threat status, and leverage the effect of updates on the lifetimes of data items in insiders\u27 knowledgebases to prevent the threat without affecting the availability of data items. Furthermore, the dissertation uses the aforementioned idea in ordering the operations of concurrent tasks such that write operations that update risky data items in knowledgebases are executed before the risky data items can be used in unauthorized inferences. In addition to unauthorized knowledge, the dissertation discusses how insiders can make unauthorized modifications in sensitive data items. It introduces new approaches to build Modification Graphs that demonstrate the authorized and unauthorized data items which insiders are able to update. To prevent this threat, the dissertation provides two methods, which are hiding sensitive dependencies and denying risky write requests. In addition to traditional RDBMS, the dissertation investigates insider threat in cloud relational database systems (cloud RDMS). It discusses the vulnerabilities in the cloud computing structure that may enable insiders to launch attacks. To prevent such threats, the dissertation suggests three models and addresses the advantages and limitations of each one. To prove the correctness and the effectiveness of the proposed approaches, the dissertation uses well stated algorithms, theorems, proofs and simulations. The simulations have been executed according to various parameters that represent the different conditions and environments of executing tasks

Enforcing privacy via access control and data perturbation.

With the increasing availability of large collections of personal and sensitive information to a wide range of user communities, services should take more responsibility for data privacy when disseminating information, which requires data sharing control. In most cases, data are stored in a repository at the site of the domain server, which takes full responsibility for their management. The data can be provided to known recipients, or published without restriction on recipients. To ensure that such data is used without breaching privacy, proper access control models and privacy protection methods are needed. This thesis presents an approach to protect personal and sensitive information that is stored on one or more data servers. There are three main privacy requirements that need to be considered when designing a system for privacy-preserving data access. The first requirement is privacy-aware access control. In traditional privacy-aware contexts, built-in conditions or granular access control are used to assign user privileges at a fine-grained level. Very frequently, users and their privileges are diverse. Hence, it is necessary to deploy proper access control on both subject and object servers that impose the conditions on carrying out user operations. This thesis defines a dual privacy-aware access control model, consisting of a subject server that manages user privileges and an object server that deals with granular data. Both servers extract user operations and server conditions from the original requests and convert them to privacy labels that contain access control attributes. In cross-domain cases, traditional solutions adopt roaming tables to support multiple-domain access. However, building roaming tables for all domains is costly and maintaining these tables can become an issue. Furthermore, when roaming occurs, the party responsible for multi-domain data management has to be clearly identified. In this thesis, a roaming adjustment mechanism is presented for both subject and object servers. By defining such a dual server control model and request process flow, the responsibility for data administration can be properly managed. The second requirement is the consideration of access purpose, namely why the subject requests access to the object and how the subject is going to use the object. The existing solutions overlook the different interpretations of purposes in distinct domains. This thesis proposes a privilege-oriented, purpose-based method that enhances the privacy-aware access control model mentioned in the previous paragraph. It includes a component that interprets the subject's intention and the conditions imposed by the servers on operations; and a component that caters for object types and object owner's intention. The third requirement is maintaining data utility while protecting privacy when data are shared without restriction on recipients. Most existing approaches achieve a high level of privacy at the expense of data usability. To the best of our knowledge, there is no solution that is able to keep both. This thesis combines data privacy protection with data utility by building a framework that defines a privacy protection process flow. It also includes two data privacy protection algorithms that are based on Chebyshev polynomials and fractal sequences, respectively. Experiments show that the both algorithms are resistant to two main data privacy attacks, but with little loss of accuracy