Research And Implementation Of Covert Channel Based On Radio Access Network Protocol Stack Control Plane

Communication security is the key to ensuring confidentiality of the country's military and political information.Traditionally,information is encrypted through an encryption algorithm for the security of the content,meta-information being exposed,however,the communication process is not secured,which leave the potential of interception and decryption of the information.Based on the traditional cryptography,covert channels provide a secret communication method under a high security scenario accomplishing the protection of the communication process.This paper studies the covert channels for 5G access networks to solve the low covertness and low robustness of unreliable transmission of covert information.In terms of the low covertness caused by the traditional covert channels using users' data as covert carriers,which makes detectors finding hidden communication by detecting communication behaviors possible,this paper proposes a control-plane-signaling-based design strategy of concealed carriers.Also,a covert information coding method is designed to construct a covert channel based on RAN control plane.The covert channels being independent of users' data is built to improve the concealment.The robustness of traditional covert channels tends to be low,as lacking the error control mechanism,the hidden information between the two sides of the communication are inconsistent.This paper designs an error control method for covert channels which is based on the RLC layer of AM transmission mode and implements window mechanism to transmit the hidden information reliably and rise the robustness.An anti-detection method based on entropy adjustment is suggested regarding that traditional cover channels could be easily detected.The signaling probability distribution of covert channels then corresponds the distribution of normal channels,which disables detection methods based on relative entropy,and the ability to anti-detection is increased.This paper designs and implements a covert channel of RAN control plane based on OAI platform,and verifies the covertness and the robustness of the channel through experiments.Experimental findings show that the covert channel proposed in this paper could resist detection methods based on relative entropy;the covert communication behavior therefore would not be detected by the detection methods,and the covertness is verified.At the same time,the consistency of the covert information between senders and receivers is ensured in the case of a poor communication environment,which verifies the robustness.