Algorithm Design For Covert Communications In Wireless Open-Access Networks

The openness of wireless networks is one of the foundations of the Internet of Everything.The open network provides an efficient and convenient communication environment,such as the extensive application of the Internet of vehicles,the Internet of Things,the industrial Internet of Things and the intelligent medical service,providing convenient life services for the public.However,due to the existence of the attacker or the eavesdropper,communication eavesdropping and privacy data leakage often occur,which seriously threatens the security of wireless network communication.For example,in the network with a passive eavesdropper in it,communication behaviors and messages between devices may be stolen and abused by the eavesdropper,resulting in privacy data leakage.In view of open network communication eavesdropping and data security problems,currently commonly used covert communication strategies,such as physical layer security technology,prevent communication from being eavesdropped by reducing the signal strength of the eavesdropping channel,but this method is applied to multiple messages Tao case;The secure multi-party computing strategy usually adopts cryptographic method to encrypt data,but this method usually has high energy consumption.At present,lightweight open network devices are gradually widely used because of their small size,fast speed,low energy consumption and flexible use,but their hidden communication problems are difficult to be solved by the above strategies.Therefore,it is still a great challenge to realize efficient and covert communication among lightweight devices in a single channel.Based on this,the covert communication algorithm of lightweight devices in a single channel in open networks with a passive eavesdropper is studied in this work.Specifically,according to the transmission power assignment to the device,it can be divided into two casses:uniform power and arbitrary power assignment.1)The equipment transmits signals with uniform power.Firstly,the transmitting power of all nodes is the same under the homogeneous device.In wireless networks with given communication links and Ad Hoc networks without infrastructure,the covert communication algorithms based on link scheduling and broadcast are designed respectively.2)The equipment transmits signals with arbitrary power.The transmitting power of equipment is an important factor affecting the communication efficiency.The existence of one distributed covert link scheduling algorithm and the upper bound of the algorithm running time are studied in wireless networks with given communication links.In addition,the conditions of covert communication and the range of safe and dangerous communication are defined in Ad Hoc networks,and a general conversion framework is given to transform algorithms without considering eavesdropping into covert communication algorithms.The main contributions of this paper are.summarized as follows:(1)A centralized covert communication algorithm is designed in an open wireless network with given links under uniform power assignment.In view of the existence of communication interference in a single channel,the covert communication problem is transformed into a covert link scheduling problem,and the problem is proved to be NP-hard.Based on the cooperative jamming model,a friendly jammer is set up to construct the cooperative jamming communication model,and a random algorithm based on greedy strategy is designed.According to the decreasing order of link length,the algorithm selects the corresponding partition set successively,and finally obtains the covert scheduling scheme,so as to realize the covert communication.The running time of this algorithm is only O(logn)times that of the optimal covert communication scheme.(2)A distributed covert communication algorithm is designed in an open wireless network with given links under uniform power assignment.Since wireless network devices are independent of each other,distributed algorithm is more suitable and more stable.By decreasing the probability of each device sending messages independently,communication interference between links is reduced.The artificial noise continuously emitted by the jammer can not only interfere with the eavesdropper’s interception of legitimate communications,but also interfere with legitimate links.Therefore,with the assistance of the friendly jammer,this paper studies how to interfere with the eavesdropper,while ensuring the normal process of legitimate communications.Based on affectance definition of link interference measure,the correctness and covetness of the algorithm are proved,and the approximate ratio between the running time of the algorithm and the optimal concealment communication mechanism is only O(log n).(3)The running time limit of covert communication algorithm for a given link in open wireless networks is studied at any power.Because there are many devices in the network,it is more appropriate to set the transmitting power of devices to arbitrary power.We consider the problem of covert communication when the device power is arbitrary and prove the existence of the distributed algorithm whose running time is O(log log Δ logn)-approximate to the optimal covert link scheduling algorithm.(4)The covert problem in Ad Hoc networks is studied under unform power.First,the conditions and scope of covert communication are given,and the sender and receiver are divided into three areas.The whole network space is divided into safe area,dangerous area and grey area,which correspond to the communication status of safe,dangerous and unknown respectively.Secondly,the Ad Hoc network covert communication based on broadcast is constructed-In addition,a general covert algorithm conversion framework is presented,which can transform the existing algorithms without considering the problem of eavesdropping into a covert algorithm with the same time complexity.