Automatic Compliance of Privacy Policies in Federated Digital Identity

Privacy [13] in the digital world is an important problem which is becoming even more pressing as new collaborative applications are developed. The lack of privacy preserving mechanisms is particularly problematic in federated identity management contexts. In such a context, users can seamlessly interact with a variety of federated web services, through the use of single-sign-on mechanisms and the capability of sharing personal data among these web services. Because of the latter feature, user’s privacy is at a stake, if the sharing of such data among federated service providers is not properly controlled to ensure that privacy is preserved and user’s privacy preferences are complied with. Current federated identity managed solutions adopt simplistic approaches to privacy management, based on contractual/legal approaches and/or limited simple checks on users’ privacy preferences. We argue that more comprehensive privacy policies (consisting of access control and obligation constraints, along with privacy preferences) should be stated by federated service providers and proactively checked by these providers, before disclosing users’ data to federated partners. To address such requirements, we introduce mechanisms and algorithms for policy compliance checking between federated service providers, based on an innovative policy subsumption approach. We formally introduce and analyze our approach. We also show how our approach is suitable for deployment and application in existing federated identity management solutions, such as Liberty Alliance, WS-* and Shibboleth.