Quantification of Information Flow in a Smart Grid

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The key to computer security is the notion of information flow. Information flow occurs either explicitly or implicitly in a system. In cyber-physical systems (CPSs), complicated interactions occur frequently between computational components and physical components. Thus, detecting and quantifying information flow in these systems is more difficult than it is in purely cyber systems. In CPSs, failures and attacks are either from the physical infrastructure, or from cyber part of data management and communication protocol, or a combination of both. As the physical infrastructure is inherently observable, aggregated physical observations can lead to unintended cyber information leakage. The computational portion of a CPS is driven by algorithms. Within algorithmic theory, the online problem considers input that arrives one by one and deals with extracting the algorithmic solution through an advice tape without knowing some parts of input. In this paper, a smart grid CPS is examined from an information flow perspective, physical values constitute an advice tape. As such, system confidentiality is violated through cyber to physical information flow. An approach is generalized to quantify the information flow in a CPS.