Audit-based Compliance Control (AC2) for EHR Systems

Traditionally, medical data is stored and processed using paper-based files. Recently, medical facilities have started to store, access and exchange medical data in digital form. The drivers for this change are mainly demands for cost reduction, and higher quality of health care. The main concerns when dealing with medical data are availability and confidentiality. Unavailability (even temporary) of medical data is expensive. Physicians may not be able to diagnose patients correctly, or they may have to repeat exams, adding to the overall costs of health care. In extreme cases availability of medical data can even be a matter of life or death. On the other hand, confidentiality of medical data is also important. Legislation requires medical facilities to observe the privacy of the patients, and states that patients have a final say on whether or not their medical data can be processed or not. Moreover, if physicians, or their EHR systems, are not trusted by the patients, for instance because of frequent privacy breaches, then patients may refuse to submit (correct) information, complicating the work of the physicians greatly. \ud \ud In traditional data protection systems, confidentiality and availability are conflicting requirements. The more data protection methods are applied to shield data from outsiders the more likely it becomes that authorized persons will not get access to the data in time. Consider for example, a password verification service that is temporarily not available, an access pass that someone forgot to bring, and so on. In this report we discuss a novel approach to data protection, Audit-based Compliance Control (AC2), and we argue that it is particularly suited for application in EHR systems. In AC2, a-priori access control is minimized to the mere authentication of users and objects, and their basic authorizations. More complex security procedures, such as checking user compliance to policies, are performed a-posteriori by using a formal and automated auditing mechanism. To support our claim we discuss legislation concerning the processing of health records, and we formalize a scenario involving medical personnel and a basic EHR system to show how AC2 can be used in practice. \ud \ud This report is based on previous work (Dekker & Etalle 2006) where we assessed the applicability of a-posteriori access control in a health care scenario. A more technically detailed article about AC2 recently appeared in the IJIS journal, where we focussed however on collaborative work environments (Cederquist, Corin, Dekker, Etalle, & Hartog, 2007). In this report we first provide background and related work before explaining the principal components of the AC2 framework. Moreover we model a detailed EHR case study to show its operation in practice. We conclude by discussing how this framework meets current trends in healthcare and by highlighting the main advantages and drawbacks of using an a-posteriori access control mechanism as opposed to more traditional access control mechanisms

Contributions to the privacy provisioning for federated identity management platforms

Identity information, personal data and user’s profiles are key assets for organizations and companies by becoming the use of identity management (IdM) infrastructures a prerequisite for most companies, since IdM systems allow them to perform their business transactions by sharing information and customizing services for several purposes in more efficient and effective ways. Due to the importance of the identity management paradigm, a lot of work has been done so far resulting in a set of standards and specifications. According to them, under the umbrella of the IdM paradigm a person’s digital identity can be shared, linked and reused across different domains by allowing users simple session management, etc. In this way, users’ information is widely collected and distributed to offer new added value services and to enhance availability. Whereas these new services have a positive impact on users’ life, they also bring privacy problems. To manage users’ personal data, while protecting their privacy, IdM systems are the ideal target where to deploy privacy solutions, since they handle users’ attribute exchange. Nevertheless, current IdM models and specifications do not sufficiently address comprehensive privacy mechanisms or guidelines, which enable users to better control over the use, divulging and revocation of their online identities. These are essential aspects, specially in sensitive environments where incorrect and unsecured management of user’s data may lead to attacks, privacy breaches, identity misuse or frauds. Nowadays there are several approaches to IdM that have benefits and shortcomings, from the privacy perspective. In this thesis, the main goal is contributing to the privacy provisioning for federated identity management platforms. And for this purpose, we propose a generic architecture that extends current federation IdM systems. We have mainly focused our contributions on health care environments, given their particularly sensitive nature. The two main pillars of the proposed architecture, are the introduction of a selective privacy-enhanced user profile management model and flexibility in revocation consent by incorporating an event-based hybrid IdM approach, which enables to replace time constraints and explicit revocation by activating and deactivating authorization rights according to events. The combination of both models enables to deal with both online and offline scenarios, as well as to empower the user role, by letting her to bring together identity information from different sources. Regarding user’s consent revocation, we propose an implicit revocation consent mechanism based on events, that empowers a new concept, the sleepyhead credentials, which is issued only once and would be used any time. Moreover, we integrate this concept in IdM systems supporting a delegation protocol and we contribute with the definition of mathematical model to determine event arrivals to the IdM system and how they are managed to the corresponding entities, as well as its integration with the most widely deployed specification, i.e., Security Assertion Markup Language (SAML). In regard to user profile management, we define a privacy-awareness user profile management model to provide efficient selective information disclosure. With this contribution a service provider would be able to accesses the specific personal information without being able to inspect any other details and keeping user control of her data by controlling who can access. The structure that we consider for the user profile storage is based on extensions of Merkle trees allowing for hash combining that would minimize the need of individual verification of elements along a path. An algorithm for sorting the tree as we envision frequently accessed attributes to be closer to the root (minimizing the access’ time) is also provided. Formal validation of the above mentioned ideas has been carried out through simulations and the development of prototypes. Besides, dissemination activities were performed in projects, journals and conferences.Programa Oficial de Doctorado en Ingeniería TelemáticaPresidente: María Celeste Campo Vázquez.- Secretario: María Francisca Hinarejos Campos.- Vocal: Óscar Esparza Martí