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A Dynamic Coding Scheme to Prevent Covert Cyber-Attacks in Cyber-Physical Systems

Mahdi Taheri, Khashayar Khorasani, Nader Meskin

TL;DR

This work addresses covert cyber-attacks in cyber-physical systems by deriving necessary and sufficient disruption-resource conditions that define which input and output channels must be compromised. It then introduces a dynamic coding scheme with an encoder and decoder to shield the CPS, proving that with one secure input and two secure outputs, covert attacks can be prevented under specified design conditions. The authors formulate a horizon-based I/O model, utilize relative-degree concepts to avoid heavy controllability analyses, and validate the approach through a numerical flight-control case study. The findings offer a practical defense mechanism for CPS operators and suggest avenues for extending the method to distributed, multi-agent settings.

Abstract

In this paper, we address two main problems in the context of covert cyber-attacks in cyber-physical systems (CPS). First, we aim to investigate and develop necessary and sufficient conditions in terms of disruption resources of the CPS that enable adversaries to execute covert cyber-attacks. These conditions can be utilized to identify the input and output communication channels that are needed by adversaries to execute these attacks. Second, this paper introduces and develops a dynamic coding scheme as a countermeasure against covert cyber-attacks. Under certain conditions and assuming the existence of one secure input and two secure output communication channels, the proposed dynamic coding scheme prevents adversaries from executing covert cyber-attacks. A numerical case study of a flight control system is provided to demonstrate the capabilities of our proposed and developed dynamic coding scheme.

A Dynamic Coding Scheme to Prevent Covert Cyber-Attacks in Cyber-Physical Systems

TL;DR

This work addresses covert cyber-attacks in cyber-physical systems by deriving necessary and sufficient disruption-resource conditions that define which input and output channels must be compromised. It then introduces a dynamic coding scheme with an encoder and decoder to shield the CPS, proving that with one secure input and two secure outputs, covert attacks can be prevented under specified design conditions. The authors formulate a horizon-based I/O model, utilize relative-degree concepts to avoid heavy controllability analyses, and validate the approach through a numerical flight-control case study. The findings offer a practical defense mechanism for CPS operators and suggest avenues for extending the method to distributed, multi-agent settings.

Abstract

In this paper, we address two main problems in the context of covert cyber-attacks in cyber-physical systems (CPS). First, we aim to investigate and develop necessary and sufficient conditions in terms of disruption resources of the CPS that enable adversaries to execute covert cyber-attacks. These conditions can be utilized to identify the input and output communication channels that are needed by adversaries to execute these attacks. Second, this paper introduces and develops a dynamic coding scheme as a countermeasure against covert cyber-attacks. Under certain conditions and assuming the existence of one secure input and two secure output communication channels, the proposed dynamic coding scheme prevents adversaries from executing covert cyber-attacks. A numerical case study of a flight control system is provided to demonstrate the capabilities of our proposed and developed dynamic coding scheme.

Paper Structure

This paper contains 10 sections, 5 theorems, 17 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Problem Statement and Formulation
  3. State-Space Representation of the CPS Under Cyber-Attacks
  4. Input/Output Model of the CPS Under Cyber-Attacks
  5. Objectives
  6. Covert Cyber-Attacks
  7. The Coding Scheme
  8. Design Specifications of the Dynamic Coding Scheme for Securing the CPS Against Covert Cyber-Attacks
  9. Numerical Case Study: Flight Control System of a Fighter Aircraft
  10. Conclusion

Key Result

Lemma 1

The triple $({C},{A},{B})$ is left-invertible if and only if $\text{rank}(P(\lambda))=n+m$ for all but finitely many $\lambda\in\mathbb{C}$, where is the Rosenbrock system matrix.

Figures (4)

  • Figure 1: The dynamic coding scheme, where $u_\text{e}(k)$ is the output of the encoder and $u_\text{d}(k)$ is the output of the decoder.
  • Figure 2: Covert cyber-attack while the first input and the first output communication channels are compromised.
  • Figure 3: Covert cyber-attack while actuators $2,\, 3$, and $4$ along with sensor $1$ are compromised.
  • Figure 4: Covert cyber-attack in presence of the dynamic coding scheme.

Theorems & Definitions (14)

  • Definition 1: Left-Invertibility ctfls
  • Lemma 1: ctfls
  • Definition 2: Covert Cyber-Attacks
  • Definition 3
  • Theorem 1
  • proof
  • Remark 1
  • Corollary 1
  • proof
  • Remark 2
  • ...and 4 more