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Expressing Security Policies

[This blog post was conceived by Steve Chong, at Harvard, and co-authored with Michael Hicks.]

Enforcing information security is increasingly important as more of our sensitive data is managed by computer systems. We would like our medical records, personal financial information, social network data, etc. to be “private,” which is to say we don’t want the wrong people looking at it. But while we might have an intuitive idea about who the “wrong people” are, if we are to build computer systems that enforce the confidentiality of our private information, we have to turn this intuition into an actionable policy.

Defining what exactly it means to “handle private information correctly” can be subtle and tricky. This is where programming language techniques can help us, by providing formal semantic models of computer systems within which we can define security policies for private information. That is, we can use formal semantics to precisely characterize what it means for a computer system to handle information in accordance with the security policies associated with sensitive information. Defining security policies is still a difficult task, but using formal semantics allows us to give security policies an unambiguous interpretation and to explicate the subtleties involved in “handling private information correctly.”

In this blog post, we’ll focus on the intuition behind some security policies for private information. We won’t dig deeply into¬†formal semantics for policies, but we provide links to relevant technical papers at the end of the post. Later, we also briefly mention how PL techniques can help enforce policies of the sort we discuss here.

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Filed under Semantics, Software Security