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Research Interests
My current research interests lie in reasoning about access control policies on the web. I am interested in the trade-off between expressiveness of the policy language and the analysis services that can be provided for it.
Currently, I am exploring using decidable subsets of First-Order logic (Description Logics or Datalog) to provide analysis services for expressive web services policy languages (such as WS-Policy and XACML).
More information is available in my thesis proposal below. Also, you can visit our WS-Policy project page
or visit my publications page for more info.
Thesis Proposal
With the widespread use of web services, there is a need for adequate security
and privacy support to protect the sensitive information these services could provide.
As a result, there has been a great interest in access control policy languages for web
services which accommodate large, open, distributed and heterogeneous environments
like the web. Currently, the languages with largest momentum include XACML (an
expressive, general purpose XML-based language that can be used to specify policies
on web resources) and WS-Policy, a policy language for web services.
With these expressive languages, a new problem has emerged: it becomes much
harder for security administrators to understand the overall effects and consequences
of their policies. Even checking that the access policy will not result in the leakage
of permissions to an unintended or unauthorized principal ( i.e., safety enforcement ),
has become difficult, if not impossible to do manually. Underspecified security policies
might unintentionally give access to an intruder. How can a security administrator
be certain that her policy covers all possible corner cases? In the cases when the administrator
does discover a bug and fixes the policy accordingly, the consequences of
that fix (change) are difficult to analyze. It is possible that due to subtle interactions of
some other policy rules with the fix, other security holes are opened. To be certain their
security policies express the desired safety requirements, policy administrators
could benefit from automated tools that can formally verify policies against safety
properties and suggest possible fixes in cases errors are found.
The goal of my research is to develop a logic-based framework that provides means
for automated analysis and verification of expressive access control policy languages for
web services. As basis for this framework I use Description Logics (DL), which are a
family of formalisms that are decidable subsets of First-Order logic, and the basis for
theWeb Ontology Language (OWL). Because of the correspondence of policy analysis
services to DL reasoning services (e.g., change analysis and verification can be
reduced to concept satisfiability and policy containment to subsumption), the framework can provide a variety of novel services
and leverage off-the-shelf optimized DL reasoners. Being based on Description Logics,
the policy framework is a) expressive, because it captures common policy idioms such
as separation of duty, role cardinality constraints, role hierarchies, conflict resolution
and negative authorizations, and b) analyzable because DL can provide all of the aforementioned
services in a manner more efficient than using full FOL theorem provers.
The analysis framework also benefits from the web-like nature of OWL-DL, which
makes it convenient for expressing policies for web services.
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