Trust Building and Usage Control for Electronic Business Processes

Information technology (IT) supports companies to streamline their business processes. The main contributions of IT are the digitalization of data and efficient communication networks, which allow companies to automatize their business processes and thus increase their efficiency, i.e., their value creation. This effort started with the optimization of internal business processes within a company. Nowadays, it also includes external business processes, in which multiple enterprises and even customers are involved. However, using IT also causes undesirable side effects for companies. They are exposed to a wide range of vulnerabilities and threats. Digitalizing data, e.g., documents, spurs the access to that data and the exchange of it. However, a disadvantageous result of digitalizing data is the increased risk of unauthorized access to that data. Communication networks provide an excellent foundation for collaboration between companies. At the same time, the open and anonymous character of communication networks is a reason for distrust towards business partners offering their goods and services over such networks. As a result of these undesirable side effects, the outcome of a certain business process supported by IT may be suboptimal or companies may refrain from using IT. Against this background, this thesis focuses on securing electronic business processes with regard to two aspects, i.e., building trust in open networks and controlling the usage of digital objects. Trust is the prerequisite for all kinds of commercial transactions. Using reputation information is one possible way to build up trust among business partners. In this thesis, we propose two new reputation systems to establish trust for ad-hoc processes in open markets. The first reputation system facilitates trust building in the context of electronic negotiations which are performed with the help of a centralized system. The reputation system enables companies to find trustworthy business partners and provides decision support during a negotiation. The second reputation system supports trust building in decentralized Peer-to-Peer (P2P) networks. A main feature of this system is its robustness against coalition attacks, which is proven with the help of a simulation. Controlling the usage of digital objects demands two functionalities. First, we need methods for defining usage rules. Second, mechanisms for enforcing the defined usage rules are required. In this thesis, we address both aspects of usage control. Digital documents play a central role in business processes, since they are a means of integration and are handled among business partners. Some documents are sensitive and thus have to be protected from being accessed by unauthorized parties. For this purpose, we propose a flexible and expressive access control model for electronic documents. Our model captures the information about the operations performed on documents. This history information can be used to define access control rules. Customers are involved in the execution of special kinds of business processes, such as selling and consuming digital goods. In these cases, digital goods have to be protected from being used in an unauthorized way, e.g., being shared in public networks. Thus, the trustworthiness of customers' platforms has to be verified before transferring digital goods. For this, we propose a robust integrity reporting protocol which is necessary when a remote platform has to perform security relevant operations, e.g., to enforce a security policy which controls the usage of digital content. This integrity reporting protocol is a building block of a new Digital Rights Management system which is also presented in this thesis. This system provides a high protection level. At the same time, it allows users to transfer their purchased content to other devices or users.

DACA: arquitetura para implementação de mecanismos dinâmicos de controlo de acesso em camadas de negócio

Doutoramento em Ciências da ComputaçãoAccess control is a software engineering challenge in database applications. Currently, there is no satisfactory solution to dynamically implement evolving fine-grained access control mechanisms (FGACM) on business tiers of relational database applications. To tackle this access control gap, we propose an architecture, herein referred to as Dynamic Access Control Architecture (DACA). DACA allows FGACM to be dynamically built and updated at runtime in accordance with the established fine-grained access control policies (FGACP). DACA explores and makes use of Call Level Interfaces (CLI) features to implement FGACM on business tiers. Among the features, we emphasize their performance and their multiple access modes to data residing on relational databases. The different access modes of CLI are wrapped by typed objects driven by FGACM, which are built and updated at runtime. Programmers prescind of traditional access modes of CLI and start using the ones dynamically implemented and updated. DACA comprises three main components: Policy Server (repository of metadata for FGACM), Dynamic Access Control Component (DACC) (business tier component responsible for implementing FGACM) and Policy Manager (broker between DACC and Policy Server). Unlike current approaches, DACA is not dependent on any particular access control model or on any access control policy, this way promoting its applicability to a wide range of different situations. In order to validate DACA, a solution based on Java, Java Database Connectivity (JDBC) and SQL Server was devised and implemented. Two evaluations were carried out. The first one evaluates DACA capability to implement and update FGACM dynamically, at runtime, and, the second one assesses DACA performance against a standard use of JDBC without any FGACM. The collected results show that DACA is an effective approach for implementing evolving FGACM on business tiers based on Call Level Interfaces, in this case JDBC.Controlo de acesso é um desafio para a engenharia de software nas aplicações de bases de dados. Atualmente, não há uma solução satisfatória para a implementação dinâmica de mecanismos finos e evolutivos de controlo de acesso (FGACM) ao nível das camadas de negócio de aplicações de bases de dados relacionais. Para solucionar esta lacuna, propomos uma arquitetura, aqui referida como Arquitetura Dinâmica de Controlo de Acesso (DACA). DACA permite que FGACM sejam dinamicamente construídos e atualizados em tempo de execução de acordo com as políticas finas de controlo de acesso (FGACP) estabelecidas. DACA explora e utiliza as características das Call Level Interfaces (CLI) para implementar FGACM ao nível das camadas de negócio. De entre as características das CLI, destacamos o seu desempenho e os diversos modos para acesso a dados armazenados em bases de dados relacionais. Na DACA, os diversos modos de acesso das CLI são envolvidos por objetos tipados derivados de FGACM, que são construídos e atualizados em tempo de execução. Os programadores prescindem dos modos tradicionais de acesso das CLI e passam a utilizar os dinamicamente construídos e atualizados. DACA compreende três componentes principais: Policy Server (repositório de meta-data dos FGACM), Dynamic Access Control Component (componente da camada de negócio que é responsável pela implementação dos FGACM) e Policy Manager (broker entre DACC e Policy Server). Ao contrário das soluções atuais, DACA não é dependente de qualquer modelo de controlo de acesso ou de qualquer política de controlo de acesso, promovendo assim a sua aplicabilidade a muitas e diversificadas situações. Com o intuito de validar DACA, foi concebida e desenvolvida uma solução baseada em Java, Java Database Connectivity (JDBC) e SQL Server. Foram efetuadas duas avaliações. A primeira avalia DACA quanto à sua capacidade para dinamicamente, em tempo de execução, implementar e atualizar FGACM e, a segunda, avalia o desempenho de DACA contra uma solução sem FGACM que utiliza o JDBC normalizado. Os resultados recolhidos mostram que DACA é uma solução válida para implementar FGACM evolutivos em camadas de negócio baseadas em CLI