18 research outputs found
Risk-based Security Measure Allocation Against Injection Attacks on Actuators
This article considers the problem of risk-optimal allocation of security
measures when the actuators of an uncertain control system are under attack. We
consider an adversary injecting false data into the actuator channels. The
attack impact is characterized by the maximum performance loss caused by a
stealthy adversary with bounded energy. Since the impact is a random variable,
due to system uncertainty, we use Conditional Value-at-Risk (CVaR) to
characterize the risk associated with the attack. We then consider the problem
of allocating the security measures which minimize the risk. We assume that
there are only a limited number of security measures available. Under this
constraint, we observe that the allocation problem is a mixed-integer
optimization problem. Thus we use relaxation techniques to approximate the
security allocation problem into a Semi-Definite Program (SDP). We also compare
our allocation method across different risk measures: the worst-case
measure, the average (nominal) measure, and across different search
algorithms: the exhaustive and the greedy search algorithms. We depict the
efficacy of our approach through numerical examples.Comment: Submitted to IEEE Open Journal of Control Systems (OJ-CSYS
Risk Assessment of Stealthy Attacks on Uncertain Control Systems
In this article, we address the problem of risk assessment of stealthy
attacks on uncertain control systems. Considering data injection attacks that
aim at maximizing impact while remaining undetected, we use the recently
proposed output-to-output gain to characterize the risk associated with the
impact of attacks under a limited system knowledge attacker. The risk is
formulated using a well-established risk metric, namely the maximum expected
loss. Under this setups, the risk assessment problem corresponds to an
untractable infinite non-convex optimization problem. To address this
limitation, we adopt the framework of scenario-based optimization to
approximate the infinite non-convex optimization problem by a sampled
non-convex optimization problem. Then, based on the framework of dissipative
system theory and S-procedure, the sampled non-convex risk assessment problem
is formulated as an equivalent convex semi-definite program. Additionally, we
derive the necessary and sufficient conditions for the risk to be bounded.
Finally, we illustrate the results through numerical simulation of a
hydro-turbine power system
A Zero-Sum Game Framework for Optimal Sensor Placement in Uncertain Networked Control Systems under Cyber-Attacks
This paper proposes a game-theoretic approach to address the problem of
optimal sensor placement against an adversary in uncertain networked control
systems. The problem is formulated as a zero-sum game with two players, namely
a malicious adversary and a detector. Given a protected performance vertex, we
consider a detector, with uncertain system knowledge, that selects another
vertex on which to place a sensor and monitors its output with the aim of
detecting the presence of the adversary. On the other hand, the adversary, also
with uncertain system knowledge, chooses a single vertex and conducts a
cyber-attack on its input. The purpose of the adversary is to drive the attack
vertex as to maximally disrupt the protected performance vertex while remaining
undetected by the detector. As our first contribution, the game payoff of the
above-defined zero-sum game is formulated in terms of the Value-at-Risk of the
adversary's impact. However, this game payoff corresponds to an intractable
optimization problem. To tackle the problem, we adopt the scenario approach to
approximately compute the game payoff. Then, the optimal monitor selection is
determined by analyzing the equilibrium of the zero-sum game. The proposed
approach is illustrated via a numerical example of a 10-vertex networked
control system.Comment: 8 pages, 3 figues, Accepted to the 61st Conference on Decision and
Control, Cancun, December 202
Design of multiplicative watermarking against covert attacks
This paper addresses the design of an active cyberattack detection
architecture based on multiplicative watermarking, allowing for detection of
covert attacks. We propose an optimal design problem, relying on the so-called
output-to-output l2-gain, which characterizes the maximum gain between the
residual output of a detection scheme and some performance output. Although
optimal, this control problem is non-convex. Hence, we propose an algorithm to
design the watermarking filters by solving the problem suboptimally via LMIs.
We show that, against covert attacks, the output-to-output l2-gain is unbounded
without watermarking, and we provide a sufficient condition for boundedness in
the presence of watermarks.Comment: 6 page conference paper accepted to the 60th IEEE Conference on
Decision and Contro
Risk-averse controller design against data injection attacks on actuators for uncertain control systems
In this paper, we consider the optimal controller design problem against data
injection attacks on actuators for an uncertain control system. We consider
attacks that aim at maximizing the attack impact while remaining stealthy in
the finite horizon. To this end, we use the Conditional Value-at-Risk to
characterize the risk associated with the impact of attacks. The worst-case
attack impact is characterized using the recently proposed output-to-output
-gain (OOG). We formulate the design problem and observe that it is
non-convex and hard to solve. Using the framework of scenario-based
optimization and a convex proxy for the OOG, we propose a convex optimization
problem that approximately solves the design problem with probabilistic
certificates. Finally, we illustrate the results through a numerical example.Comment: Accepted for publication to the 2022 American Control Conferenc
Joint controller and detector design against data injection attacks on actuators
This paper addresses the issue of data injection attacks on actuators in control systems. Considering attacks that aim at maximizing impact while remaining undetected, the paper revisits the recently proposed output-to-output gain, which is compared to classical sensitivity metrics such as H-infinity and H_. In its original formulation, the output-to-output gain is unbounded for strictly proper systems. This limitation is further investigated and addressed by modifying the performance output of the system and ensuring that the system from attack signal to performance output is also strictly proper. With this system description, and by using the theory of dissipative systems, a Bi-linear Matrix Inequality (BMI) is formulated for system design. Using this BMI, a design algorithm is proposed based on the heuristic of alternating minimization. Through numerical simulations of the proposed algorithm, it is found that the output-to-output gain presents advantages over the other metrics: the effect of the attack is reduced in the performance output and increased in the detection output in a relatively large spectrum of frequencies
Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel-tungsten composite coatings
Silicon carbide (SiC) reinforced nickel-tungsten (Ni-W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni-W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni-W-5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni-W-5 g/l SiC coating was showed higher corrosion resistance (i.e. similar to 21% increase in corrosion potential, E-corr) compared to Ni-W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni-W-5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO4 and SiO2. (C) 2015 Elsevier B.V. All rights reserved