A substantial amount of research on the security of cyber-physical systems assumes that the physical system model is available to the adversary. In this paper, we argue that such an assumption can be relaxed, given that the adversary might still be able to identify the system model by observing the control input and sensory data from the system. In such a setup, the attack with the goal of identifying the system model using the knowledge of input-output data can be categorized as a Known-Plaintext Attack (KPA) in the information security literature. We first prove a necessary condition and a sufficient condition, under which the adversary can successfully identify the transfer function of the physical system. We then provide a low-rank controller design which renders the system unidentifiable to the adversary, while trading off the LQG performance.

This Authorea document template can be used to prepare documents according to a desired citation style and authoring guidelines. Abstracts are not always required, but most academic papers have one and writers should know how to produce a useful abstract. An abstract should be a very short, clear and concise summation of the entire paper.An abstract should provide enough of a preview that a typical reader will know whether or not they wish to read the paper. It should reveal both the purpose and conclusions of the paper.IntroductionThe format of this template follows a typical journal publication with an introduction, results and conclusion. Examples of an equation, list and citation are also included. The purpose of the introductionMost academic introductions follow an ‘inverted pyramid’ structure: they start broad and narrow down to a specific thesis or research question. The introduction should reveal:some broad knowledge of the overall topicreferences to related and prior work in the field of investigationsuccinct overview of the major point of the paperResultsThis section is only included in papers that rely on primary research. This section catalogues the results of the experiment. The results should be presented in a clear and unbiased way. Most results sections will contain links and citations, e.g., \cite{Feynman_1986}, and equations, e.g. \(e^{i\pi}+1=0\).ConclusionThe conclusion should reinforce the major claims or interpretation in a way that is not mere summary. The writer should try to indicate the significance of the major claim/interpretation beyond the scope of the paper but within the parameters of the field. The writer might also present complications the study illustrates or suggest further research the study indicates is necessary.