SECURITY-AWARE WAVEFORMS FOR ENHANCING WIRELESS COMMUNICATIONS PRIVACY IN CYBER-PHYSICAL SYSTEMS VIA MULTIPATH RECEPTIONS
ABSTRACT
Cyber-Physical System (CPS), regarded as the nextgeneration of engineered system, has the capability to interactwith the real physical world. Applications of CPS span variousfields such as medical monitoring, traffic control, and smartgrid. With such widespread applications, privacy assurance isbecoming more and more important since what the CPS connectsare people and the real world. Any leakage of private informationwill cause serious consequences. In this paper, we focus onenhancing the secrecy of wireless communications in CPS byuse of physical layer security techniques. Specifically, we studyan amplify and forward (AF) relay network where all devicesareequipped with a single antenna. We propose a privacy-enhancedwaveform design approach aided by artificial noise (AN) toenhance the communication secrecy in a wireless environmentwith multipath receptions. First, we consider the case with perfecteavesdropper’s channel state information (CSI). We optimizethe AF coefficient for forwarding the information-bearing signaland the AN covariance to maximize the achievable secrecyrate. The optimal solution is obtained by solving a series ofsemidefinite programs (SDPs). Then, a more practical scenariowith imperfect eavesdropper’s CSI is studied. We develop arobust waveform design method and obtain the lower boundof the achievable secrecy rate. Numerical results are presentedto show the effectiveness of our proposed algorithms.
EXISTING SYSTEM:
The basic security requirements of CPS include robust-ness to unpredictable conditions, self-healing capabilities, andappropriate assurances in terms of authentication, integrity,serviceavailability, and non-repudiation of the informationflows. However, different kinds of external maliciousattacks are threatening the security of CPS, such as denial-ofservice(DoS) attack and false-data injection (FDI) attack. Severalresearches have been conducted to defeat specific attacksn specific CPS applications .studiedthe real-time detection of DoS attacks in vehicular networksunder the random jamming attack and on-off jamming attack.In, the optimal FDI attack strategy and the correspondingtwo defense schemes were proposed. In , the authorsstudied the effect of replay attacks on a control system andproposed a detection method.Apart from the aforementioned security requirements, privacyor secrecy is also an essential characteristic of a trustworthyCPS. Privacy issues in CPS mainly refer to the leakage of personalsensitive information. The main reason for informationleakage is that the CPS highly depends on the communicationnetworks and heterogeneous IT elements. Furthermore,the widely used wireless communications in CPS make theconfidential information much more vulnerable to eavesdroppingattack. The traditional anti-eavesdropping strategy isbased on the cryptographic encryption. However, withthe enhancement of eavesdroppers’ computing capabilities, theencryption method faces an increasing risk of informationleakage. Moreover, the management and distribution of thesecret keys often require complex protocols and architectures,which makes the cryptographic method difficult to be appliedin the CPS especially the Internet of Things (IoT) withdistributed resource-constrained devices
PROPOSED SYSTEM:
In this paper, we concentrate on the confidential messagetransmission from a source (e.g., wearable medical device) to adestination (e.g., doctor’s smartphone) in a medical CPS. Dueto the lack of direct source-destination link, one pre-selectedrelay is employed to help forward the message. During thetransmission, an eavesdropper is attempting to extract thisconfidential message. We try to enhance the security of thisrelay network by performing security-aware waveform design.Unlike, we consider a more practical scenario wherethe destination uses the maximum ratio combining (MRC)receiver, the complexity of which is much lower than theminimum mean square error (MMSE) receiver in [39]. What’smore, we also study the robust waveform design with imperfecteavesdropper’s channel state information (CSI).the maincontributions of this paper can be summarized as follows:1) The secure relay-aided SISO transmission is studied interms of waveform design for the first time. The relay usesan AN-aided amplify-and-forward (AF) protocol to forwardthe confidential message.2) With perfect CSIs of legitimate links and the eavesdroppinglink, we optimize the AF coefficient for informationbearingsignal and the AN covariance to maximize theachievable secrecy rate. The optimal solution is obtainedthrough convex optimization.3) With imperfect CSI of the eavesdropping link, to make theproblem tractable we enlarge the space of estimation errorwhich strengthens the CSI uncertainty constraint. Then wetransform the secrecy rate maximization problem into asemidefinite program (SDP) and obtain the optimal robustAF coefficient and AN covariance. Since the uncertaintyconstraint has been strengthened, the maximum achievablesecrecy rate after optimization is actually the lower boundof the original problem.
CONCLUSIONS
Although CPS is expected to produce enormous economicbenefits, it is vulnerable to many kinds of malicious attacksdue to the employment of communication networks. Athese attacks, privacy is becoming a very critical issue sincewhat the CPS connects is the real physical world and thusany information leakage will cause serious consequences. Westudied the privacy-enhanced waveform design method for aSISO relay network with multipath receptions. Specifically, weproposedan AN-AF strategy which required the relay to forwardthe source message and inject artificial noise at the sametime. We first studied the case with perfect eavesdropper’sCSI. The AF coefficient for forwarding information-bearingsignal and the AN covariance were optimized to maximizethe achievable secrecy rate. We obtained the optimal solutionby using a one-dimensional search and solving a series ofSDPs. Then, we considered a more practical scenario wherethere exists channel estimation error for eavesdropper’s CSI.Totackle this problem, we enlarged the estimation error spaceand then obtained the lower bound of the achievable secrecyrate. Numerical examples were presented to show the performancesof the proposed schemes under different simulationenvironments. Simulation results demonstrate that although theinjectedAN will cause interference to the legitimate user, itis still helpful for increasing secrecy rate.
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