  In Cyber-Physical Systems (CPS), inference based on communicated data is of
critical significance as it can be used to manipulate or damage the control
operations by adversaries. This calls for efficient mechanisms for secure
transmission of data since control systems are becoming increasingly
distributed over larger geographical areas. Distortion based security, recently
proposed as one candidate for secure transmissions in CPS, is not only more
appropriate for these applications but also quite frugal in terms of prior
requirements on shared keys. In this paper, we propose distortion-based metrics
to protect CPS communication and show that it is possible to confuse
adversaries with just a few bits of pre-shared keys. In particular, we will
show that a linear dynamical system can communicate its state in a manner that
prevents an eavesdropper from accurately learning the state.
