A Trust Degree Based Method For Trustworthy Friendly Jammer Selection

With the rapid development of information technology,great changes have taken place in society and economy.At the same time,many security issues and challenges also follow.The significance of information security is very important.It is related to citi-zens' privacy and national security.Therefore,all countries regard information security as a major national strategy.In the current information communication,the proportion of wireless communication networks is increasing,and the broadcasting nature of wireless transmission makes information security face great challenges.In this case,the issue of in-formation security in wireless communication networks has gradually become a research hot issue.In addition,eavesdroppers' equipments are also developing rapidly,gradually improving the ability to crack encryption methods,and constantly challenging the secrecy performance of traditional encryption methods.In order to meet these challenges,re-searchers have proposed physical layer security technology to supplement and strengthen encryption methods.The physical layer security technology protects information secu-rity by using the characteristics of the wireless channel,such as time-varying characteris-tics and random characteristics.Among them,cooperative jamming technology can well realize information security transmission,and is very commonly used in physical layer security technology.In the cooperative jamming technology,if the source node needs to transmit information to the destination node,a friendly jammer will be selected.The jammer sends a certain power interference signal to the eavesdropper,and then the source node will provide a certain reward to the jammer in return.Under the interference of the jammer,the eavesdropper cannot correctly decode the information transmitted in the channel,so that secure information transmission can be carried out between the source node and the destination node.In the cooperative jamming technology,the method of selecting jammers is very im-portant,and it is related to the quality of network secrecy performance.However,the current method for selecting cooperative jammers has the following limitations:1)Since each candidate jammer hopes to be selected to obtain rewards,the candidate nodes will report channel state information(CSI)to increase their chances of being selected.Such dishonest candidate nodes will cause unfairness on the one hand,and reduce the secrecy performance of the entire network on the other hand.In addition,the jammer may be selfish when sending jamming signals,only sending part(or even not sending)jamming signals to the eavesdropper,and then get undue rewards.2)The trust model for the analy-sis and selection of untrusted j ammers has not been studied yet.On the one hand,due to the mobility of wireless nodes,the spatial topology of wireless networks is highly dynamic.Therefore,the trust model must be flexible and able to adapt to the dynamic changes of the network space.On the other hand,considering the time dimension,the jammers may have dynamic behaviors at different time intervals.Therefore,the trust model must be able to respond differently to these dynamic behaviors in different time intervals.3)For the behavior of jammers,it is impractical to define it only from the perspective of"dual-ism"(trusted or untrusted).In fact,jammers may have different degrees of untrustworthy behavior,that is,"multiple behaviors".How to evaluate such"multiple behaviors" of jammers has not been studied yet.In view of the above limitations,this paper studies the method of selecting trusted jammers based on the trust degree,so as to select trustworthy friendly jammers.The main contributions of this paper are summarized as follows:·In order to deal with the dishonest and untrustworthy behaviors of candidate jam-mers,at the physical layer,this paper firstly encourages the jammers based on the Vickrey auction strategy,so that the candidate jammers will ensure honesty when reporting CSI.Secondly,this article uses energy detection method to detect whether the j ammer sends interference signals.In the social layer,the trust category and trust degree are innovatively introduced to evaluate the trust degree of each candidate jammer.Specifically,by observing its interference behavior,an additive multiply-ing and multiplying algorithm is used to update the trustworthiness of the jammer.Finally,according to the updated trust level and trust category,a trusted j ammer can be selected.·In order to adapt to the spatial dynamics of the network and the time dynamics of the nodes,this paper creatively designs two trust models,namely the Beta trust model for the dynamics of the network space and the hidden Markov model(HMM)for the temporal dynamics of the nodes.In both models,the trustworthiness of the jam-mer is quantified as the trust degree.In the Beta trust model for spatial dynamics,the probability of the interference signal detection result is represented by the Beta distribution.Specifically,the Beta trust model allows the use of detection results obtained from direct detection and/or indirect detection.This ability to combine results from different detections ensures that the Beta trust model is flexible and can therefore be applied to networks with strong spatial topologies.In the time ori-ented HMM trust model,the time interval between node dynamic detection results is considered,which makes it possible to capture the behavioral time characteristics of jammers.This means that the trust model of HMM can adapt well to the time dynamics of nodes.·In order to quantify and evaluate the multiple behaviors of j ammers,this paper inno-vatively introduces the Dirichlet trust model,and uses multiple results to evaluate the multiple behaviors of jammers.Since a single energy threshold cannot adapt to the fluctuation of the received interference signal,it cannot detect the multiple behaviors of the jammer.This paper proposes an energy detection method with multiple thresholds.Using the multi-threshold energy detection method,multiple detection results can be obtained,so that the jammers can be divided into multi-ple levels.In order to provide scores with these multiple levels,this paper builds a trust model based on the Dirichlet distribution.The trust model can classify the reputation value and normalize it to a trust degree.In the Dirichlet trust model,the posterior(updated)reputation value is calculated by combining the a priori(previ-ous)reputation value with the new rating.Finally,this paper assigns a weight value to each rating of the reputation value,and calculates the normalized reputation value as the trust degree to evaluate the credibility of the jammer.The thesis consists of 5 chapters,including 45 figures and 156 references.