Research On Privacy Protection In Cognitive Radio Networks

The rapid development of wireless communication technology not only comes with an increasing number of wireless devices but puts more pressure on limited spectrum resources as well.That becomes a serious problem for further development of wireless communications.Cognitive radio technology,which improves spectrum utilization and thus to alleviate spectrum shortage,is a critical part of next-generation wireless communication.Based on cognitive radio technology,Cognitive Radio Networks(CRNs)enable spectrum reuse in time,space and frequency domain by sharing spectrum among primary users(PUs)and secondary users(SUs).Thus,CRNs are considered as the solid foundation of future wireless communications.However,during spectrum sharing in CRNs,there is a high risk of privacy leakage in both spectrum sensing and spectrum access phases.SUs will be unwilling to take part in spectrum sensing or even refuse to use CRNs for communications at all,once their privacy is threatened.This definitely hinders the development of CRNs.This thesis focuses on identity and location privacy preservation of CRNs in spectrum sensing phase and spectrum access phase as well,which is of both academic and practical significance,and the corresponding solutions are proposed.The main contributions are summarized as follows.Firstly,a privacy-preserving data aggregation scheme with fault tolerance for spectrum sensing is proposed.The elliptic curve cryptography technique over a finite field is utilized to generate pseudonyms for SUs.The real identities of SUs are kept secret from others except the trusted certificate authority such that SUs’ identity privacy is preserved.Moreover,SUs encrypt sensing reports related to locations with random keys generated by the trusted certificate authority,and then submit encrypted reports with different pseudonyms each time.That implies no one can obtain identities of SUs based on sensing reports and the connections between SUs and locations are cut off as well.Thus,location privacy of SUs is preserved.On the other hand,if some SUs fail to submit their sensing reports,then random keys can be canceled out by the trusted certificate authority,such that the spectrum management center is still able to compute the sum of remaining SUs.This indicates the fault tolerance of the proposed scheme.Secondly,we propose a reliable privacy-preserving data aggregation scheme without a trusted certificate authority for spectrum sensing.The scheme employs Schnorr blind signature to generate anonymous certificates and reputation certificates for SUs.SUs submitted sensing reports with anonymous certificates to preserve identity privacy.In addition,each SU obtains a new anonymous certificate from the spectrum management center every time they participate in spectrum sensing,and no one is able to map sensing reports to a specific SU such that location privacy of SUs is preserved.Furthermore,to ease the impact of malicious SUs who tend to offer false reports,the weighted average of sensing reports is provided based on SUs’ reputations for reliable data aggregation.Thirdly,a dynamic real-time channel allocation framework is proposed for spectrum access.SUs request available channels from base stations instead of the spectrum management center,which protects the location privacy of SUs to some extent.Meanwhile,multiple base stations cope with SUs’ requirements to offload the spectrum management center and further ease the impact of its unavailability.Based on the framework,a privacy-preserving spectrum access scheme with channel reservation is proposed.The elliptic curve cryptography technique is employed to generate pseudonyms for SUs to provide identity privacy protection during channel request.Similarly,multiple pseudonyms of each SU make it more unlikely to build a connection between the identity and locations of a specific SU,such that location privacy of SUs is thus protected.In addition,this framework learns the number of channels required for each base station from reservation,and then assigns the corresponding number of channels in advance.Furthermore,the elliptic curve cryptography technique is proved to be efficient in channel allocation to shorten the time of available channel acquisition.Finally,we propose a privacy-preserving spectrum access scheme without channel reservation to reduce information leakage.In general,a Poisson distribution based spectrum demand prediction is developed to obtain the number of channels needed in each base station.Then,the modular square root technique is employed to generate unlinkable pseudonyms,which cut off the connection between SUs and their locations for location privacy protection.More importantly,integrating the framework with the modular square root technique reduces the overhead of spectrum access,such that the channel allocation is improved efficiently for better user experience.