Research On Data Covert Transmission Mechanism Based On Anonymous Communication Network

In the current social environment with the rapid development of information technology,the Internet has been integrated into all aspects of social operation.The wide application of the Internet makes cyberspace security particularly important,and the data security requirements of some government departments also put forward higher requirements for communication protection.Covert communication is a type of technical method that hides the actual communication behavior of users in other communication processes to protect the communication behavior from being discovered.This technology has important applications in scenarios with high security requirements because of its high communication security.Network covert channel is the main form of covert communication in the field of network communication.It belongs to one-to-one communication mode.Once its concealment is destroyed,attackers can easily obtain the address information of both sides of covert communication through overt channel.Therefore,the traditional network covert channel has the problem of lack of anonymity,and network covert channel with anonymity has important research value.In practical applications,the anonymity network represented by Tor can provide anonymity enhancement services to protect the communication relationship between the two parties.Therefore,this paper chooses to build a network covert channel based on Tor which is widely deployed to realize covert communication with anonymity.The specific research work of this paper includes the following four aspects:Firstly,a network covert channel model based on anonymous communication network is designed.Aiming at the anonymity defect of traditional network covert channel,the concept of Anonymous Network Covert Channel is proposed and a conceptual model is given.Then,based on Tor,two types of Anonymous Network Covert Channels are proposed without relying on third parties and based on third parties,and their scenarios are described respectively.According to the characteristics of different models,evaluation indicators such as robustness,channel capacity,concealment,and anonymity are proposed.Secondlly,two Anonymous Network Covert Channel schemes that do not rely on third parties are designed.Based on the mechanism of Tor anonymous communication,a timing covert communication scheme based on anonymous communication flow rate is designed by adding dummy packets to the overt channel to modulate the flow rate.Based on the mechanism of Tor hidden service introduction circuit,a storage covert communication scheme based on the hidden service introduction link is designed by rewriting INTRODUCE1 cell in the RC,PK and padding field.After evaluation,the above schemes can achieve high robustness and channel capacity with good concealment and anonymity.Thirdly,two Anonymous Network Covert Channel schemes based on third parties are designed.Based on the domain name registration and query mechanism of Tor hidden service directory server,a storage covert communication scheme based on hidden service domain name status is designed by modulating the domain name status of different directory servers by hidden service.Based on the mechanism of Tor hidden service descriptor,a storage covert communication scheme based on covert service descriptor is designed by using the padding part.After evaluation,the above storage schemes can achieve high robustness and channel capacity and good concealment and anonymity.Finally,based on the above research results,an anonymous data covert transmission system is designed and implemented.The system consists of three modules: user interface module,out-of-band channel,and modulation and demodulation module.The user interface module realizes parameter input and real-time communication visualization.The out-of-band channel module and the modulation and demodulation module realize data concealment communication.The practical deployment verifies the practicability of the system.To sum up,this thesis proposes and implements covert communication technologies based on anonymous network.These technologies effectively make up for the anonymity defect of the traditional network covert channel model and improve the security of data communication.this thesis realizes an anonymous data covert transmission system based on these technologies.It can provide support for data communication scenarios with high security requirements.