published_or_final_version / abstract / Computer Science / Doctoral / Doctor of Philosophy

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Collaborative environments allow users to share and access data across networks spanning multiple administrative domains and beyond organisational boundaries. This poses several security concerns such as data confidentiality, data privacy and threats to improper data usage. Traditional access control mechanisms focus on centralised systems and implicitly assume that all resources reside in the one domain. This serves as a critical limitation for inter-organisational collaborative environments, which are characteristically decentralised, distributed and heterogeneous. A consequence of the lack of suitable access control mechanisms for inter-organisational collaborative environments is that data owners relinquish all control over data they release. In these environments, we can reasonably consider more complex cases where documents may have multiple contributors, all with differing access control requirements. Facilitating such cases, as well as maintaining control over the document’s content, its structure and its flow path as it circulates through multiple administrative domains, is a non-trival issue. This thesis proposes an architecture model for specifying and enforcing access control restrictions on sensitive data that follows a pre-defined inter-organisational workflow. Our approach is to embed access control enforcement within the workflow object (e.g. the circulating document containing sensitive data) as opposed to relying on each administrative domain to enforce the access control policies. The architecture model achieves this using cryptographic access control – a concept that relies on cryptography to enforce access control policies.

M.Sc. (Computer Science) / Client/Server computing is currently one of the buzzwords in the computer industry. The client/server environment can be defined as an open systems environment. This openness of the client/server environment makes it a very popular environment to operate in. As information are exceedingly accessed in a client/server manner certain security issues arise. In order to address this definite need for a secure client/server environment it is necessary to firstly define the client/server environment. This is accomplished through defining three possible ways to partition programs within the client/server environment. Security, or secure systems, have a different meaning for different people. This dissertation defines six attributes of information that should be maintained in order to have secure information. For certain environments some of these attributes may be unnecessary or of lesser importance. Different security techniques and measures are discussed and classified in terms of the client/server partitions and the security attributes that are maintained by them. This is presented in the form of a matrix and provides an easy reference to decide on security measures in the client/server environment in order to protect a specific aspect of the information. The importance of a security policy and more specifically the influence of the client/server environment on such a policy are discussed and it is demonstrated that the framework can assist in drawing up a security policy for a client/server environment. This dissertation furthermore defines an electronic document .management system as a case study. It is shown that the client/server environment is a suitable environment for such a system. The security needs and problems are identified and classified in terms of the security attributes. Solutions to the problems are discussed in order to provide a reasonably secure electronic document management system environment.

M.Com. (Accounting) / Please refer to full text to view abstract

The increasing reliance on information technology to support business processes has emphasised the need for information security mechanisms. This, however, has resulted in an ever-increasing workload in terms of security administration. Security administration encompasses the activity of ensuring the correct enforcement of access control within an organisation. Access rights and their allocation are dictated by the security policies within an organisation. As such, security administration can be seen as a policybased approach. Policy-based approaches promise to lighten the workload of security administrators. Separation of duties is one of the principles cited as a criterion when setting up these policy-based mechanisms. Different types of separation of duty policies exist. They can be categorised into policies that can be enforced at administration time, viz. static separation of duty requirements and policies that can be enforced only at execution time, viz. dynamic separation of duty requirements. This dissertation deals with the specification of both static separation of duty requirements and dynamic separation of duty requirements in role-based workflow environments. It proposes a model for the specification of separation of duty requirements, the expressions of which are based on set theory. The model focuses, furthermore, on the enforcement of static separation of duty. The enforcement of static separation of duty requirements is modelled in terms of invariant conditions. The invariant conditions specify restrictions upon the elements allowed in the sets representing access control requirements. The sets are themselves expressed as database tables within a relational database management system. Algorithms that stipulate how to verify the additions or deletions of elements within these sets can then be performed within the database management system. A prototype was developed in order to demonstrate the concepts of this model. This prototype helps demonstrate how the proposed model could function and flaunts its effectiveness.

M.Com. (Computer Auditing) / The need to evaluate today's complex computer environments from an audit perspective has increased, particularly in viewof the disappearance of a paper audit trail and the inefficiencies of auditing "around" the computer in these environments. By making use of the Access Path and the Path Context Models, it was possible to carry out an evaluation of the MVS/XA environment. This evaluation was carried out using the methodology developed in this research essay. This methodology may have universal applicability in the evaluation of computer security. The concept of each layer in the access path being a "net", which only allows authorised users to drop to the next layer, was applied. It was found that each systems software component had sufficient facilities to meet the control objectives. The operating system itself, however, was found to present the installation with more risk factors than controls. It was therefore concluded that an external access control software package needs to be implemented to supplement the controls in this environment, if the control objectives are to be met. It was also concluded that the implementation of this package would not, in itself, solve all the security issues, and that the matrices developed should be used in the implementation of this package. This is a further indication of the usefulness of the model and the methodology. The applicability of the Access Path and the Path Context Models in the evaluation of the predefined environment has therefore been established.

D.Phil. (Computer Science) / The need for security in a database is obvious. Object-orientation enables databases to be used in applications where other database models are not adequate. It is thus clear that security of object-oriented databases must be investigated...

Workflow systems have gained popularity not only as a research topic, but also as a key component of Enterprize Resource Planning packages and e- business. Comprehensive workflow products that automate intra- as well inter-organizational information flow are now available for commercial use. Standardization efforts have centered mostly around the interoperability of these systems, however a standard access control model have yet to be adopted. The research community has developed several models for access control to be included as part of workflow functionality. Commercial systems, however, are still implementing access control functionality in a proprietary manner. This dissertation investigates whether a comprehensive model for gain- ing context-sensitive access control, namely CoSAWoE, can be purposefully implemented in a commercial workflow product. Using methods such as an exploratory prototype, various aspects of the model was implemented to gain an understanding of the di±culties developers face when attempting to map the model to existing proprietary software. Oracle Workflow was chosen as an example of a commercial workflow product. An investigtion of the features of this product, together with the prototype, revealed the ability to affect access control in a similar manner to the model: by specifying access control constraints during administration and design, and then enforcing those constraints dynamically during run-time. However, only certain components within these two aspects of the model directly effected the commercial workflow product. It was argued that the first two requirements of context-sensitive access control, order of events and strict least privilege, addressed by the object design, role engineering and session control components of the model, can be simulated if such capabilities are not pertinently available as part of the product. As such, guidelines were provided for how this can be achieved in Oracle Workflow. However, most of the implementation effort focussed on the last requirement of context-sensitive access control, namely separation of duties. The CoSAWoE model proposes SoD administration steps that includes expressing various business rules through a set of conflicting entities which are maintained outside the scope of the workflow system. This component was implemented easily enough through tables which were created with a relational database. Evaluating these conflicts during run-time to control worklist generation proved more di±cult. First, a thorough understanding of the way in which workflow history is maintained was necessary. A re-usable function was developed to prune user lists according to user involvement in previous tasks in the workflow and the conflicts specified for those users and tasks. However, due to the lack of a central access control service, this re- usable function must be included in the appropriate places in the workflow process model. Furthermore, the dissertation utilized a practical example to develop a prototype. This prototype served a dual purpose: firstly, to aid the author's understanding of the features and principles involved, and secondly, to illustrate and explore the implementation of the model as described in the previous paragraphs. In conclusion the dissertation summarized the CoSAWoE model's compo- nents which were found to be product agnostic, directly or indirectly imple- mentable, or not implemented in the chosen workflow product. The lessons learnt and issues surrounding the implementation effort were also discussed before further research in terms of XML documents as data containers for the workfow process were suggested.

Due to the correspondence between the role abstraction in Role-based Access Control (RBAC) and the notion of organizational positions, it seems easy to construct role hierarchies. This is, however, a misconception. This paper argues that, in order to reflect the functional requirements, a role hierarchy becomes very complex. In a bid to simplify the design of role hierarchies suitable for the expression of access control requirements in workflow systems, the paper proposes a “typed” role hierarchy. In a “typed” role hierarchy a role is of a speci fic type. The associations between different types of roles are limited by rules that govern the construction of a role hierarchy. This paper proposes a methodology to systematically construct a “typed” role hierarchy. Since the “typed” nature of the role hierarchy is only relevant during the construction of the role hierarchy, it can seamlessly be integrated into existing RBAC schemes that support the concept of role hierarchies. / Eloff, J.H.P., Prof.