Adding Privacy Protection to Policy Based Authorisation Systems

An authorisation system determines who is authorised to do what i.e. it assigns privileges to users and provides a decision on whether someone is allowed to perform a requested action on a resource. A traditional authorisation decision system, which is simply called authorisation system or system in the rest of the thesis, provides the decision based on a policy which is usually written by the system administrator. Such a traditional authorisation system is not sufficient to protect privacy of personal data, since users (the data subjects) are usually given a take it or leave it choice to accept the controlling organisation’s policy. Privacy is the ability of the owners or subjects of personal data to control the flow of data about themselves, according to their own preferences. This thesis describes the design of an authorisation system that will provide privacy for personal data by including sticky authorisation policies from the issuers and data subjects, to supplement the authorisation policy of the controlling organisation. As personal data moves from controlling system to controlling system, the sticky policies travel with the data. A number of data protection laws and regulations have been formulated to protect the privacy of individuals. The rights and prohibitions provided by the law need to be enforced by the authorisation system. Hence, the designed authorisation system also includes the authorisation rules from the legislation. This thesis describes the conversion of rules from the EU Data Protection Directive into machine executable rules. Due to the nature of the legislative rules, not all of them could be converted into deterministic machine executable rules, as in several cases human intervention or human judgement is required. This is catered for by allowing the machine rules to be configurable. Since the system includes independent policies from various authorities (law, issuer, data subject and controller) conflicts may arise among the decisions provided by them. Consequently, this thesis describes a dynamic, automated conflict resolution mechanism. Different conflict resolution algorithms are chosen based on the request contexts. As the EU Data Protection Directive allows processing of personal data based on contracts, we designed and implemented a component, Contract Validation Service (ConVS) that can validate an XML based digital contract to allow processing of personal data based on a contract. The authorisation system has been implemented as a web service and the performance of the system is measured, by first deploying it in a single computer and then in a cloud server. Finally the validity of the design and implementation are tested against a number of use cases based on scenarios involving accessing medical data in a health service provider’s system and accessing personal data such as CVs and degree certificates in an employment service provider’s system. The machine computed authorisation decisions are compared to the theoretical decisions to ensure that the system returns the correct decisions

My private cloud--granting federated access to cloud resources

We describe the research undertaken in the six month JISC/EPSRC funded My Private Cloud project, in which we built a demonstration cloud file storage service that allows users to login to it, by using their existing credentials from a configured trusted identity provider. Once authenticated, users are shown a set of accounts that they are the owners of, based on their identity attributes. Once users open one of their accounts, they can upload and download files to it. Not only that, but they can then grant access to their file resources to anyone else in the federated system, regardless of whether their chosen delegate has used the cloud service before or not. The system uses standard identity management protocols, attribute based access controls, and a delegation service. A set of APIs have been defined for the authentication, authorisation and delegation processes, and the software has been released as open source to the community. A public demonstration of the system is available online

On Properties of Policy-Based Specifications

The advent of large-scale, complex computing systems has dramatically increased the difficulties of securing accesses to systems' resources. To ensure confidentiality and integrity, the exploitation of access control mechanisms has thus become a crucial issue in the design of modern computing systems. Among the different access control approaches proposed in the last decades, the policy-based one permits to capture, by resorting to the concept of attribute, all systems' security-relevant information and to be, at the same time, sufficiently flexible and expressive to represent the other approaches. In this paper, we move a step further to understand the effectiveness of policy-based specifications by studying how they permit to enforce traditional security properties. To support system designers in developing and maintaining policy-based specifications, we formalise also some relevant properties regarding the structure of policies. By means of a case study from the banking domain, we present real instances of such properties and outline an approach towards their automatised verification.Comment: In Proceedings WWV 2015, arXiv:1508.0338