deal with attacks over cognitive radio networks authenticationognitive radio

Deal with attacks over cognitive radio networks authentication

Saeideh TaheriSchool of Computer

Engineering, Iran Universityof Science & Technology

Tehran, [email protected]

Ahmad SharifiSchool of Information

Technology, JawaharlalNehru Technological

University, Hyderabad, [email protected]

Reza BerangiSchool of Computer

Engineering, Iran Universityof Science & Technology

Tehran, [email protected]

Abstract

According to the recent development, we look forwardto further widespread use of wireless networks soon.Thus one of the issues that we face to them is shortageof spectrum. Cognitive radio networks (CRNs) are anappropriate way to overcome this deficiency and alsoCRNs increase productivity and efficiency of spectrum.

The crucial assumption is that secondary user shouldnot interfere with primary user, therefore when primaryuser does not use of spectrum, usage permission of thisspectrum is given to authorized secondary user. Sothere must be a secure way for CRNs authenticationand it must be able to deal with the attacks in CRNsauthentication. In this paper we discuss aboutclassification and attacks definition, dangers and risksin wireless networks and CR and eventually we proposea new method for preventing attacks in CRNs based onID encryption in the encrypting method based on twoencryption keys.

Keywords: Cognitive radio networks, Authentication,Attacks, ID, Key, Encryption

1. IntroductionRadio spectrum is a valuable and limited resource thattransmitters and receivers must get permission from therelevant organization for using it. In 2002, the FederalCommunications Commission (FCC) released a reportaimed at improving using methods of this valuableresource in the United States. Among FCC findings andrecommendations noted to this point that if weconsidered the entire radio spectrum we will understand

that a number of frequency bands of the spectrum, areoften useless and in some of them, only a part of thecapacity and in the others, a large parts of the frequencybands are used.

Non-optimal use of the electromagnetic spectrum, leadto the definition of holes frequency. The permission ofan electromagnetic hole has been given to the primaryuser, but it has not been used at a certain time andplace. Now if the secondary user accesses this hole,there will be a significant improvement in thespectrum. Thus the cognitive radio is the appropriateway for an optimum use of the spectrum that usesfrequency holes as opportunistic uses.

Cognitive radio was first introduced by Mitola in1998.Mitola has defined cognitive radio as follow:Opportunistic access to the bands that we are not theirowner, without causing intolerable interference tolicensed users of bandwidth.

Cognitive radio is an intelligent wirelesscommunication technology that is aware of his externalenvironment and with considering it adjustsperformance parameters such as transmitter power,carrier frequency and modulation method in order totake the efficient use of the spectrum. The cognitiveradio can intelligently understand which frequencyband is empty and which one is in use so it uses ofempty bands to transmit its data [1]. There is a majorchallenge, one of them is that the attacker won't replaceitself instead of authorized secondary user with this aimthat it can use of the spectrum and the other one is thatit won’t attack to system with destruction purpose anddoesn’t interrupt the system. Due to these cases, we

Saeideh Taheri et al ,Int.J.Computer Technology & Applications,Vol 3 (6), 2027-2032

IJCTA | Nov-Dec 2012 Available [email protected]

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ought to study the attacks on the secondary user anddeal with them.

In the second part it will be paid a brief explanation incognitive radio networks and we consider the types ofarchitecture and it’s given a brief description aboutsome of the attacks against cognitive radio networks.

In the third section the types of attacks on wirelessnetworks will be reviewed and then we classify them.In the fourth part of a new method for secureauthentication of cognitive radio network will beintroduced and then the types of attacks in thisauthentication method will be studied and eventually inthe fifth part the final conclusions of this paper will bediscussed.

2. Cognitive radio network2.1. Cognitive radio networks actively detect andidentify low used spectrum and dynamically create anumber of authorized channels for using of thespectrum. (Maximizing spectrum efficiency, improvingspectrum performance, minimize interference) And theagreement in consideration of local traffic distributionand local user adjusts the bandwidth adaptively [2].

A radio transceiver is designed to automatically detectwhether a particular part of the radio spectrum is beingused or not and temporary uses of that low usedspectrum, without any interference with authorizedusers, or to abandon it [3]. The key for enablingcognitive radio networks technology, are cognitiveradio techniques which they are capable of sharing thespectrum in opportunistic ways [4]. A cognitive radiodefined as a radio, which can change its transmissionparameters based on interaction with their environment.Based on this definition two main features of cognitiveradio are defined: Cognitive capability;Reconfiguribility [5].

- Cognitive capability, through real time interactionwith the radio environment, the spectral ratios that arenot used in a particular time and place, is determined.As shown in Figure 1, cognitive radio allows thetemporary used of useless spectrum. (Spectrum hole orwhite space) Eventually the best spectrum is selectedand share with other users and it is used withoutinterfering with licensed user.

Figure 1. An overview of cognitive radio. Theconcept of spectrum hole [4]

- Reconfigurability: a cognitive radio can beprogrammed so that it can send and receive differentfrequencies and uses of different access methods thatare supported by its hardware designing. Due to thisfeature, a better spectrum band and the most suitableoperating parameters can be selected and adjusted [6].

In order to provide these capabilities, the cognitiveradio requires a new architecture of radio frequencytransceiver. Components of the cognitive radio networkarchitecture is shown in Figure 3, is divided into twogroups: the primary networks and cognitive radionetworks.

Figure 3. Architecture of cognitive radio network [4]

The primary network or authorized network: It refers toan existing network, where the main users have alicense for operation in a specific spectral band. . Ifprimary networks have infrastructure, the primary useractivities are controlled from the main base station.Because of their priority in spectrum access, theprimary users must not be affected by users withoutany permission.

Cognitive radio networks: They have no license tooperate in desired band. Therefore additional functionis necessary for cognitive radio users in order to sharethe licensed spectrum band. Users of these systems



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communicate with each other by dynamic use ofspectral holes.

In one hand, cognitive radio users are able to access tothe licensed spectrum which is not used by the primaryuser and in the other hand they can access to unlicensedspectrum, by broad-band technology. A licensed bandis used primarily by the primary user at first, Thereforecognitive radio networks have concentrated in trackingthe primary users [4]. The channel capacity depends onthe primary users' interference. Furthermore, if theprimary users appear in the spectrum bands that areoccupied by cognitive radio users, cognitive radionetworks have to leave spectrum immediately andmove to another available spectrum.

In the absence of the primary users, cognitive radiousers have the same right to access to the license bands.

Cognitive radio users have three different types ofaccess: Cognitive radio network access, cognitive radioAd-hoc access, Primary network access.

There are two types of wireless communication systemin cognitive radio networks: Main systems andcognitive radio systems, which are classified, based ontheir priorities in the frequency bands [7].

3. Classifying the attacks on wirelessnetworksSince wireless networks, are developed more and morein today's world and according to the nature of thesenetworks, which are based on radio signals, the mostsignificant point in using this technology, is beingaware of the strengths and weaknesses. Considering theawareness necessity of dangers for using thesenetworks, despite its inherent features, correctconfiguration will help to achieve to an acceptable levelof security. Totally the security points are common inthe entire wireless networks category.

The following figure shows a view of the attacksclassification:

Figure 3. Classification of attacks

According to the above tree, security attacks aredivided into two groups; active and passive.

3.1. Passive attacks

In these attacks, an unauthorized user can access tonetwork resources, However that does not alter themessage text, but it wants to use the networkinformation [8]. There are three types of passiveattacks:

- Response: In this method, the hacker accesses the tothe data channel and it doesn't damage the system, atfirst but hacker can send some message to the networkauthorized users with this aim that they think themessage is coming from the server.

- Eavesdropping: in this method, intruder listens to allexchange data over network to find the appropriatemessage from the station to the server side.

- Traffic analysis: Another way for attacking in which ahacker analyzes network traffic to find the overallpattern of the network .thus it realizes that what exactlya workstation does and how it works.

3.2. Active attacksAgainst passive attacks, in these kinds of attacks,intruder changes the information, which is obtainedfrom sources that doing these changes are notpermitted. [9] Since the information changes in thiskind of attacks, identifying of happening attacks it is apossible process. These attacks are commonly dividedinto the four following categories:- Masquerade: In this type of attack, intruder forges themain identity. This method involves changing theidentity of the connected parties or changing the actualstream of information processing.- Fake reply: In this kind of attacks intruder check thepackets which the information recipient gets on aconnection. Of course for informing of the connectionnature a link is studied of the first. But only theinformation that is sent from receiver to transmitter isuseful. This type of attack is used when the senderidentify receiver. In this case the response packets thatare sent to the sender as the response to senderquestions are considered as a flag to identify thereceiver. Therefore this can be exploited if the intruderstores these packets and when the receiver is not active,or activity or its connection is interrupted consciouslyby to the intruder. Intruder replaces as receiver withresending packets and it can gain the desirable accesslevel.Message modification: In some cases, the mostcommon and most varied kinds of active attacks aremodifying the message. Since there are various types oftraffic on the network and each of these traffic andprotocols used a method for their security management



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so for each types of these traffic, the intruder can adoptcertain types of messages modification and thereforeattacks by knowing of the various protocols.Considering the extent of this kind of attack whichcompletely depends on the type of protocol, theseattacks are not only for accessing to information butalso they can apply certain changes for misleading thetwo sides and this can provide some difficulties for thedesired level of accessing, which can be a normal user.- Denial-of-Service Attacks: This type of attack, intypical scenarios, includes the most common attacks. Inthis type of attack, the intruder or attacker wants tochange the operation or management of acommunication or information system. The simplestexample is trying to disables software and hardware. Insome cases, due to Dos attack the service won't downcompletely and only the operation will be stopped. Inthis matter the intruder can use of the same service byabusing of disturbance.

4. Studying of attacks and ways to dealwith them on the authentication ofcognitive radio networksThe primary user uses of licensed band, but sometimesthis band is not used by primary user, thus the right ofusing the band is given to secondary user for increasingproductivity and efficiency of the spectrum when it isnot used by the primary user.

The secondary user is an authorized user which theaccess right of using the primary user spectrum hasgiven to it when it's not used by primary user.

Now we must examine whether the secondary user isauthorized user or not? This is done by the secondaryuser authentication.therefore the primary user mustauthenticate secondary user to find that it is authorizedor attacker.

Secondary user sends an authentication message toprimary user and it is authenticated by that. But if thereare a lot of authentication requests for a user, it ispossible that this request is from an attacker which itwants stop system or it wants to find a secondary userlicense with checking responses.

The next mode is when the secondary user requestauthentication and it receives 2 answers which this canbe indicates that there is an attacker and in addition tothe primary user the attacker answers too.

The authentication request cannot be encrypted and ifthe authentication reply is not encrypted, the attacker

could easily find it.Now if the authentication responseis encrypted by the key k1and algorithm, it is true thatthe attacker is not able to detect it but the attacker mayattack the response actively and finally it will find keyK1. So that the secondary user sends an authenticationmessage with an identifier to primary user and weknow that primary users and secondary users alreadyhave agreed on key k1. Primary user checks thisrequest and encrypts the response by the key k1 andalgorithm A1 and the encrypted response is decoded inthe second user side by the same agreement key k1 andalgorithm A1, thus the answer is in two modes: 1 –User is authorized and it has access to the band or 2 -User is unauthorized and access is denied.

Then there is an issue here and it is that the attacker istrying to understand the key k1 and if the attacker canaccess k1, it can replace itself as secondary user anddecode the encrypted message and understand it whilereplace itself as authorized secondary user or it can usesthe spectral bands which its license has given tosecondary user or stop the system by sending so manyrequests.

Here comes passive and active attack discussion.Active attacks are that an attacker sends a large numberof requests and evaluate their responses to find the keyk1. The purpose of attacker for sending a lot of requeststo can cut off the system which it named DoS (Denialof Service) attack or it sends many requests to evaluatetheir responses. Thereby the attacker mimics thesecondary user Ids and then sends a large number ofrequests with the same ID toward the primary user andfinally the attacker can find the key k1 with evaluatingthe responses received from the primary user.

One way to deal with this attack is that to re-encrypt theencrypted answer with key K1 and algorithm A1,which is in two forms: access allowed (Ack) or accessis denied (Nack) is by another key K2 and encryptionalgorithm A2, on the primary user side and on thesecondary user side we can decrypt it. Thus it can befound that authentication is correct or not.



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Figure 4. Encryption by two encrypted keys

Even in this case the attacker can get keys, and passiveattacks issue occurs and attacker listens to the messagesand their replies passively several times and because IDhas not changed the attacker understands that all ofthem are from the same secondary user and the user hasnot changed so the attacker list all the answers in atable for comparing them to get the key. Thereforethere is a solution to deal with this attack and it is thatto change the secondary user ID for hiding this fact thatthe same user has requested re-authentication. Becausesometimes, there is no possibility of a successfulauthentication due to a problem in primary system orthe authentication process maybe takes a lot more thanthe time we have considered. Then in this cases thesecondary user request re-authentication.

4.1. Message identification Problem as a blindmessage

Another plan can be considered that there is a centerwhich primary user is connected to it and authorizedsecondary users have registered in it. Thus once asecondary user sends its ID for authentication toprimary user, primary user encrypts it with key K1 andsends it for the center and center encrypts theauthentication answer with key K2, and returns it to theprimary user. However, if the attacker is in the way, inaddition to primary user, the attacker is informed of thisanswer too, so the attacker copies the answer withoutunderstanding what the message is and because ID hasnot changed and this represents the same secondaryuser. Therefore the attacker realizes original responsewith collecting the answers. (Thereby, it checks the

reaction of a particular user, after several timesattempts for authentication and guesses the answerwithout understand what the original answer is). At lastthe attacker replaces itself as primary user and answersto secondary user.

For example when attacker observes that after aspecific response, the connection is interrupted, itrealizes this answer: access is denied, and sends theanswer to the original user. Thus the primary usercannot use of the spectrum or attacker uses thespectrum itself or the attacker reaches to its final targetthat might be just interrupting the system. Therefore theattacker has attacked ID and identified the message as ablind so this problem can be solved by the proposedmethod which include encrypting the answer with twokeys and changing the ID and the attacker won't be ableto find the answer any more because the ID is changedevery time and it does not indicate whether the user isthe previous secondary user or not.

Figure 5. Message identification as a blind message

Thus it has achieved to purpose which is establishing asecure communication.

5. ConclusionDue to the widespread use of cognitive radio networks,establishing a secure communication is especiallyimportant in these networks. In this paper it has tried toconsider a secure method based on two encryption keyand change the ID. According to this method onlyauthorized users are able to use these networks and theattacks on the secondary user authentication, whetheractive or passive, cannot be an issue in this relationshipon this network.

6. References[1] Parvin, S.; Song Han; Biming Tian; Hussain, F.K.,”

Trust-Based Authentication for SecureCommunication in Cognitive Radio Networks“,Embedded and Ubiquitous Computing (EUC), 2010IEEE/IFIP 8th International Conference on ,p 589-596,2010

[2] Yuan Yuan, Cognitive Radio Networks: From Systemand Security Perspectives, Google Inc.



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[3] Luiz Dasilva, and Allen MacKenzie, CognitiveNetworks,CrownCom 2007

[4] Akyildiz, I.F.; Won-Yeol Lee; Vuran, M.C.; Mohanty,S.,” A survey on spectrum management in cognitiveradio networks”, Communications Magazine, IEEE ,p40-48,2008

[5] Nomura, Ritsu; Kuroda, Masahiro; Mizuno,Tadanori,” Evaluation of EAP based Re-authentication Protocol for High-speedVehicularHandover in Cognitive Radio Networks “, CognitiveRadio Oriented Wireless Networks andCommunications, 2007. CrownCom 2007. 2ndInternational Conference On , p 549-553 ,2007

[6] Chen, K., Peng, Y., Prasad, N., Liang, Y., Sun, S,”cognitive radio network architecture”, ICUIMC '08Proceedings of the 2nd international conference onUbiquitous information management andcommunication,2008

[7] Wang Weifang, “Denial of service attacks in cognitiveradio networks”, Environmental Science andInformation Application Technology (ESIAT), 2010International Conference on, p 530 – 533, 2010

[8] Prasad, N.R., “Secure Cognitive Networks”, WirelessTechnology, 2008. EuWiT 2008. EuropeanConference on, p 107-110 ,2008

[9] Li Zhu; Huaqing Mao, “Research on AuthenticationMechanism of Cognitive Radio Networks Based onCertification Authority”, Computational Intelligenceand Software Engineering (CiSE), 2010 InternationalConference on , p 1-5, 2010

[10] Yi Tan; Sengupta, S.; Subbalakshmi, K.P., “Analysisof Coordinated Denial-of-Service Attacks in IEEE802.22 Networks”, Selected Areas inCommunications, IEEE Journal on , p 890-902, 2011



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