Coding Schemes for Securing Cyber-Physical Systems Against Stealthy Data Injection Attacks

Abstract

This paper considers a method of coding the sensor outputs in order to detect\nstealthy false data injection attacks. An intelligent attacker can design a\nsequence of data injection to sensors and actuators that pass the state\nestimator and statistical fault detector, based on knowledge of the system\nparameters. To stay undetected, the injected data should increase the state\nestimation errors while keep the estimation residues small. We employ a coding\nmatrix to change the original sensor outputs to increase the estimation\nresidues under intelligent data injection attacks. This is a low cost method\ncompared with encryption schemes over all sensor measurements in communication\nnetworks. We show the conditions of a feasible coding matrix under the\nassumption that the attacker does not have knowledge of the exact coding\nmatrix. An algorithm is developed to compute a feasible coding matrix, and, we\nshow that in general, multiple feasible coding matrices exist. To defend\nagainst attackers who estimates the coding matrix via sensor and actuator\nmeasurements, time-varying coding matrices are designed according to the\ndetection requirements. A heuristic algorithm to decide the time length of\nupdating a coding matrix is then proposed.\n