{"id":155310,"date":"2004-01-01T00:00:00","date_gmt":"2004-01-01T00:00:00","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/msr-research-item\/cassandra-flexible-trust-management-applied-to-electronic-health-records\/"},"modified":"2018-10-16T22:08:25","modified_gmt":"2018-10-17T05:08:25","slug":"cassandra-flexible-trust-management-applied-to-electronic-health-records","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/cassandra-flexible-trust-management-applied-to-electronic-health-records\/","title":{"rendered":"Cassandra: flexible trust management, applied to electronic health records"},"content":{"rendered":"<div class=\"asset-content\">\n<p>We study the specification of access control policy in large-scale distributed systems. We present Cassandra, a language and system for expressing policy, and the results of a substantial case study, a security policy for a national Electronic Health Record system, based on the requirements for the ongoing UK National Health Service procurement exercise. Cassandra policies are expressed in a language based on Datalog with constraints. The expressiveness of the language (and its computational complexity) can be tuned by choosing an appropriate constraint domain. Cassandra is role-based; it supports credential-based access control (e.g. between administrative domains); and rules can refer to remote policies (for automatic credential retrieval and trust negotiation). Moreover, the policy language is small, and it has a formal semantics for query evaluation and for the access control engine. For the case study we choose a constraint domain C0 that is sufficiently expressive to encode many policy idioms. The case study turns out to require many subtle variants of these; it is important to express this variety smoothly, rather than add them as ad hoc features. By ensuring only a constraint compact fragment of C0 is used, we guarantee a finite and computable fixed-point model. We use a top-down evaluation algorithm, for efficiency and to guarantee termination. The case study (with some 310 rules and 58 roles) demonstrates that this language is expressive enough for a realworld application; preliminary results suggest that the performance should be acceptable.<\/p>\n<\/div>\n<p><!-- .asset-content --><\/p>\n","protected":false},"excerpt":{"rendered":"<p>We study the specification of access control policy in large-scale distributed systems. We present Cassandra, a language and system for expressing policy, and the results of a substantial case study, a security policy for a national Electronic Health Record system, based on the requirements for the ongoing UK National Health Service procurement exercise. Cassandra policies [&hellip;]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"footnotes":""},"msr-content-type":[3],"msr-research-highlight":[],"research-area":[13558],"msr-publication-type":[193716],"msr-product-type":[],"msr-focus-area":[],"msr-platform":[],"msr-download-source":[],"msr-locale":[268875],"msr-field-of-study":[],"msr-conference":[],"msr-journal":[],"msr-impact-theme":[],"msr-pillar":[],"class_list":["post-155310","msr-research-item","type-msr-research-item","status-publish","hentry","msr-research-area-security-privacy-cryptography","msr-locale-en_us"],"msr_publishername":"","msr_edition":"17th IEEE Computer Security Foundations Workshop (CSFW)","msr_affiliation":"","msr_published_date":"2004-01-01","msr_host":"","msr_duration":"","msr_version":"","msr_speaker":"","msr_other_contributors":"","msr_booktitle":"17th IEEE Computer Security Foundations Workshop 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